Equine Rhinitis in Respiratory Infection Cases (AAEP 2011)
by: Nancy S. Loving, DVM
January 23 2012, Article # 19482, Reprinted from www.thehorse.com
When considering viral respiratory infections in horses, a common assumption among veterinarians is animals are infected with either influenza or rhinopneumonitis (a respiratory condition--mostly of young horses--caused by equine herpesvirus). However, another viral infection--equine rhinitis--is commonly responsible for respiratory disease outbreaks. Andres Diaz-Mendez, Med Vet, MSc, of the University of Guelph presented information about equine rhinitis virus A (ERAV) at the 2011 American Association of Equine Practitioners Convention, held Nov. 18-22 in San Antonio, Texas.
Diaz-Mendez described clinical signs of ERAV, which mimic those seen with equine influenza or rhinopneumonitis: nasal discharge ranging from serous (clear, runny) to mucopurulent (thick, greenish-white), fever, and cough. In one study of nasal swabs from horses with acute respiratory disease, researchers found the prevalence of influenza was 56%, ERAV was 42%, and 24% of the horses were infected with both viruses. He explained that ERAV affects both the upper and lower airways with moderate inflammation that exacerbates inflammatory airway disease (IAD) and recurrent airway obstruction (heaves).
Genome sequencing of ERAV has shown that any changes since it was first isolated in 1962 have been very minor, as the currently circulating virus is 96% similar to when it was first identified. This is in contrast to equine influenza virus, which mutates frequently.
In Diaz-Mendez's study he induced experimental infection in a dozen 8- to 12-month-old healthy ponies by suppressing their immune systems with the corticosteroid dexamethasone three days prior to viral exposure. Within 24 hours of exposure, clinical signs began to appear as fever and increased wheezing lung sounds.
Understanding Equine Medications is your A-Z guide to learning more about generic and brand-name pharmaceuticals, possible side effects and precautions, and proper dosage.
By Day 3, the ponies' submandibular (under the jaw) lymph nodes were enlarged and they had nasal discharge and tracheal mucus that was confirmed with endoscopy; the tracheal mucus persisted until Day 21. Lower airway samples revealed viral shedding Days 5 to 7. In the infected ponies an antibody response appeared by Day 7 that persisted to Day 21, along with airway inflammation lasting for three weeks. By Day 21, the lymph nodes were still enlarged but nasal discharge had abated.
Equine rhinitis virus can have a marked impact on health and performance by its effects on both the upper and lower respiratory tracts persisting for three weeks. Diaz-Mendez noted that infection with ERAV might be considerably underestimated in the equine population and, thus, practitioners should consider it when presented with a horse with acute respiratory viral infection. In addition, he pointed out that equine rhinitis virus might be associated with episodes of other respiratory conditions, such as IAD and heaves. At this time there is no vaccine available to protect against equine rhinitis virus.
Diaz-Mendez continues to research ERAV and received one of three inaugural $25,000 Boehringer Ingelheim Vetmedica Equine Research Awards at the convention for a study proposal. In a study to be completed in 2012 he'll examine the response of equine airway epithelium to ERAV infection and he'll perform viral surveillance.
PRODUCT AND EQUINE HEALTH CARE NEWS:
Couple Donates $1 Million to UPenn Laminitis Research Fund
by: Edited Press Release
November 15 2007, Article # 10821
University of Pennsylvania School of Veterinary Medicine has announced a gift of $1 million from philanthropists Marianne and John K. Castle to support its laminitis research.
"We are enormously grateful for the Castles' generosity. Their thoughtful philanthropy leverages two of the University's strengths--research and the translation of research into medicine for both animals and humans," said Penn President Amy Gutmann, PhD.
In speaking about the gift, John Castle said, "Marianne and I are thrilled to be able to support Dr. Orsini and the faculty of the University of Pennsylvania School of Veterinary Medicine in their research. Our hope is that the knowledge acquired will be important in helping both animals and humankind."
There are big plans for the funds.
"The Castles' generosity will allow us take a significant step forward in creating a research institute dedicated to sharing and advancing the breadth of knowledge about this deadly condition," said Joan C. Hendricks, VMD, PhD, the Gilbert S. Kahn Dean of Veterinary Medicine.
When fully funded, the institute will include new research laboratories, funding for research projects at Penn Vet, and in collaboration with other institutions, a home-care treatment model, support for student research opportunities, and improved clinical facilities.
In addition to funding research in laminitis, the Castles' gift will support the institute directorship, which will be held by James Orsini, DVM, Dipl. ACVS, associate professor of surgery at Penn Vet's New Bolton Center campus. In 2001, Orsini founded the First International Conference on Laminitis and Diseases of the Foot, building on his many years of experience treating patients afflicted with this condition. The biennial conference is funded in large part by the Castles, in memory of their beloved horse Spot, who died from laminitis.
Parasiticidal Resistance Reported in New Study
by: Stacey Oke, DVM, MSc
June 19 2008, Article # 12105
Kentucky researchers report that roundworms and small strongyles, two common equine intestinal parasites, are developing resistance against most of the commercially available worming products. What's worse, no new drugs against either of these parasites are forthcoming on the market.
"Since drug resistance by small strongyles and roundworms has been increasing since the late 1950s, the purpose of this study was to obtain field data regarding the efficacy of commercial wormers to obtain more information on the development of drug resistance," explained Eugene Lyons, PhD, from the University of Kentucky's Gluck Equine Research Center.
Drug resistance by small strongyles and roundworms has been increasing since the late 1950s.
Between June 1 and December 20, 2007, foals on five farms located in Central Kentucky were monitored in this field study. Efficacy of fenbendazole, oxibendazole, pyrantel pamoate, and ivermectin were evaluated by calculating the reduction in the number of foals with roundworm eggs or small strongyle eggs in their feces before versus after treatment.
"Our results showed that there was a significant reduction in roundworm eggs after treatment with fenbendazole and oxibendazole, but not ivermectin or pyrantel pamoate," summarized Lyons. "In addition, only ivermectin reduced the number of small strongyle eggs--the remaining three drugs were ineffective."
Lyons explained that while ivermectin still appears to be effective against small strongyles, research using worm count data in addition to egg count data needs to be done in order to evaluate why eggs of these parasites are returning more quickly than previously after treatment.
"In this study, we calculated eggs counts only one to two weeks post-worming. This might have been too early and providing misleading information because other studies have suggested that small strongyle eggs counts are returning more quickly than they used to post-treatment," said Lyons. (See Study: Small Strongyles Developing Resistance to Ivermectin for more on this.)
Parasite resistance to these drugs is a serious concern for horse owners, veterinarians, and the scientific community in general.
The study, "Evaluation of parasiticidal activity of fenbendazole, ivermectin, oxibendazole, and pyrantel pamoate in horse foals with emphasis on ascarids (Parascaris equorum) in field studies on five farms in Central Kentucky in 2007," was published in the July 2008 edition of Parasitology Research.
FEVER TICKS SPREADING ACROSS TEXAS COULD HAVE EQUINE IMPACT
Veterinarians from the Texas Animal Health Commission (TAHC) are worried because fever ticks (Boophilus microplus) capable of carrying and transmitting deadly cattle "tick fever" protozoans Babesia bigemina or Babesia bovis, have been detected on livestock or wildlife in 139 Texas pastures during the past 12 months. More than one million acres in Texas is under quarantine, according to a statement from the TAHC.
Horse owners are worried because this tick species can also spread Babesia equi and B. caballi protozoal parasites that attack and destroy red blood cells in horses. The resulting disease is known as piroplasmosis. (There are Babesia parasites that affect horses, cattle, dogs, cats, mice, humans, and other mammals.)
"In July 2007, the first preventive quarantine was established--39,325 acres in Starr County--to enable the U.S. Department of Agriculture's Tick Force and the TAHC to inspect and treat livestock moved from the area, get ahead of the fever tick, and push it back across the quarantine line," said Bob Hillman, DVM, Texas' state veterinarian and head of the TAHC, the state's livestock and poultry health regulatory agency, in the release. "Now, a year later, we have more than a million acres under preventive quarantines in Starr, Zapata, Jim Hogg, Maverick, Dimmit, and Webb Counties, in addition to the half-million acres in the permanent fever tick quarantine zone that runs alongside the Rio Grande, from Del Rio to Brownsville."
Equine Piroplasmosis Facts
An infectious, tick-borne disease caused by two protozoal parasites (Babesia caballi and B. equi), which attack the red blood cells.
Characterized by fever, anemia, weight loss, jaundice, and, in some cases, death.
Case fatality rate can be up to 20% in naive horses.
The only treatment is a potent type of chemotherapy that is only effective in eliminating B. caballi and can have serious side effects in some horses.
Disease is spread by ticks, the use of contaminated needles, and possibly through blood-contaminated semen of infected stallions.
Can be spread by some tick species in the United States, and a few species can pass the parasite transovarially (from mother to offspring).
Infected ticks can live for two years without feeding, and they pass the parasite while feeding.
The United States has screened all imported horses for piroplasmosis for nearly 30 years.
The fever tick, which can survive winters from coast to coast and as far north as Washington, D.C., was successfully pushed back into Mexico in 1943, according to the TAHC. Periodic tick incursions since then have occurred in Texas, but only one, in the 1970s, eclipsed the current outbreak for the number of premises infested, and that outbreak took six years to eradicate.
"Historically, fever ticks preferred cattle, and sometimes hitched a ride on horses," the TAHC statement noted. "Now fever ticks are being detected not only on white-tailed deer and nilgai (an antelope species), but also on aoudad sheep, fallow, axis, and red deer, and elk. Fighting fever ticks on a variety of species--especially free-ranging animals that don't respect fences--makes this battle much more difficult," said Hillman.
B. equi and B. caballi can be transmitted by adult and nymphal ticks of several genera, including Dermacentor, Hyalomma, Rhipicephalus, and Boophilus.
Equine piroplasmosis is a tick-borne protozoal infection of horses (EPM, equine protozoal myeloencephalitis, is another disease caused by a protozoal parasite, Sarcocystis neurona, although it is transmitted differently). It can be difficult to diagnose piroplasmosis since the parasites cause a wide variety of clinical signs, including acute fever, lack of appetite, anemia, jaundice, chronic weight loss, poor exercise tolerance, and sudden death. The disease can be fatal in up to 20% of previously unexposed animals. The tick vectors exist in the United States, and cases of piroplasmosis were seen in Florida in the 1960s. It took until 1988 before piroplasmosis was eradicated from Florida, according to Peter Timoney, MVB, PhD, FRCVS, a researcher at the University of Kentucky's Gluck Equine Research Center.
Recovered horses become chronic carriers without clinical signs.
The only treatment is a potent type of chemotherapy that should eliminate clinical signs of disease; however, it won't necessarily eliminate the parasites from infected horses. Recent research at Washington State University found that administration of a specific drug can effectively clear B. caballi from infected horses.
Piroplasmosis is found in nearly every country in the world except the United States, Canada, Australia, England, Ireland, Japan, and Iceland. It is estimated that only 10% of the world's horse population is naive (has not been exposed to or developed antibodies to one or both parasites). Therefore, it is crucial that the naïve U.S. horse population avoids exposure.
Equine piroplasmosis can also be spread by contaminated needles and syringes. Piroplasmosis can infect a fetus in utero, particularly if it's caused by B. equi. After recovery, equids can become carriers for long periods of time, probably lifelong in many cases, said Timoney. Semen from chronically infected stallions that might show no outward signs of disease could potentially spread the parasites if semen is contaminated with infected blood.
The incubation period for piroplasmosis varies between five and 21 days.
Equine piroplasmosis is considered a foreign animal disease by the USDA and, therefore, should be reported immediately to state and federal authorities, noted Timoney.
Texas' Financial Fight
"Early this year, the fever tick program received $5.2 million of the $13 million of federal funds requested to fight the tick, and while appreciated and used, it is not enough to win this battle," said Hillman in the release.
"It's really a 'pay now or pay later' scenario, because this tick won't be stopped with less than an all-out assault that requires adequate personnel, sufficient treatment products, and enough equipment, such as portable dipping vats or portable spray boxes for cattle, and treatment equipment for deer and other wildlife hosts," continued Hillman. "Texas has a ticking time bomb in south Texas. So far, we have had only two of the three elements for a 'tick fever' outbreak--fever ticks and fever tick hosts, including cattle, horses, and several species of wildlife. If, however, some of these fever ticks carry Babesia, a blood parasite deadly to cattle, the equation would be complete and we could see livestock death losses."
"Fighting fever ticks may seem simple, but it's not easy … and it's never cheap," said Hillman.
Poisonous Plant Risk Increases as Pasture Grass Goes Dormant
by: Jodi DeLong
October 14, 2008 The Horse.com E Newsletter
As autumn rolls around, pastures become depleted as grasses and other plants slow their growth prior to going dormant for winter. So, it's not surprising that this time of year can also bring an increase in reports of horses becoming ill from eating something they shouldn't have.
Karyn Bischoff, DVM, MS, Dipl. ABVT, a diagnostic toxicologist at Cornell University's New York State Animal Health Diagnostic Center, said it does appear there are more suspected cases of poison plant ingestion in late summer and autumn, but also says these are difficult to diagnose.
"Plant ingestions over time can cause chronic disease, so by the time the horse is noticeably sick, the plant is gone because it was all eaten, it's out of season, or the horses were moved to another stable or pasture after exposure," Bischoff explained.
She added that plant toxins can be difficult to find in the body as the particular toxin are sometimes not known, there are no good tests for it, or the toxin has metabolized and gone before the horse presents clinical signs of serious illness.
Happily, most toxic plants are not very palatable, and horses tend to avoid them.
Jack van Roestel, MSc, a longtime horse owner and forage consultant with AgraPoint in Kentville, Nova Scotia, stressed that prevention of poisoning begins with good pasture management.
"When it comes to grazing, it's good to have several paddocks that are rotationally grazed, with proper entrance and exit heights, rest periods, stocking numbers, and applied fertility," van Roestel said. "By having a fairly competitive grass stand, weed problems will be reduced."
Bischoff agreed that good pasture management goes a long way in preventing poisoning, but also stressed that horse owners should contact their veterinarian whenever they have concerns about health issues. "If they can't answer your questions right away, they are usually going to know the best places to find trustworthy information for you," she said.
Some wild plants to watch out for
Toxic plants will vary by the region you live in. Contact your local extension office to find out more information on noxious plants for your area. The botanical name is given first: the abbreviation spp. indicates there can be more than one species involved.
Senecio spp. Tansy ragwort, groundsel, or stinking willy
Prunus spp. Cherries, apricots, peaches and plums
Cicuta maculata. Water hemlock is one of the most poisonous plants found in North America.
Taxus spp. Yew (often used as an ornamental)
Sorghum halepense. Johnsongrass
Robinia pseudoacacia. Black locust.
Asclepias syriaca. Common milkweed
Phytolacca americana. Common pokeweed.
Pteridium aquilinum. Bracken fern.
Crotalaria spp. Rattlebox or rattlepod
Solanum spp. Bittersweet, nightshade. *Other members of the Solanum (nightshade) family including Physalis (Japanese lanterns, an ornamental) Datura (Jimsonweed) and the tomato (Lycopersicon) are also highly toxic.
Acer rubrum. Red maple. *Wilted leaves of red maple are especially toxic, but avoid feeding leaves of any maple species to horses.
Juglans nigra: Black walnut. *Avoid bedding made from sawdust or shavings of black walnut as these can cause laminitis in horses.
Astragalus and Oxytropis spp. Locoweeds. *These plants are not only toxic but addictive. Bischoff said once a horse has started eating the plant it must never again be in a pasture where locoweed is present, because it will seek the plant out.
For more on toxic plants and substances see "Poisoning in Horses: Common Toxic Substances."
TREATING SEASONAL HEADSHAKING WITH EYE DROPS
by: Stacey Oke, DVM, MSc
October 07 2008
Horses that shake their heads in an unexpected, intermittent, potentially violent, and apparently involuntary way are not only frustrating, but widely deemed unsafe for the rider or handler.
Horses suffering from seasonal headshaking can display either a vertical or horizontal movement. They might flip their noses as if an insect was up the nose, or strike at their face. These behaviors appear worse in sunny weather.
In the new report, "Treatment of seasonal headshaking in three horses with sodium cromoglycate eye drops," British veterinarians explained that an underlying cause of headshaking is only identified in a fraction of horses. To date, headshaking remains a poorly understood phenomenon and treatments, such as steroid therapy, have been met with limited success.
In horses with excessive tearing and photophobia (a sensitivity or aversion to light), sodium cromoglycate eye drops (one drop per eye four times per day) appears to markedly decrease the incidence of headshaking.
Based on these findings, the authors suggested that in some horses headshaking might be indicative of a generalized rhinitis related to an allergic condition.
Dennis Brooks, DVM, PhD, Dipl. ACVO, a professor of Ophthalmology in the Department of Small Animal Clinical Sciences at the University of Florida's College of Veterinary Medicine, commented on this report.
"Headshaking is a terrible disease for afflicted horses and their owners," emphasized Brooks. "This is a relatively inexpensive option to try and may help some horses."
In the United States, sodium cromoglygate eyedrops are available through veterinarians (known as Opticrom, it's a cromolyn sodium ophthalmic solution; a clear, sterile solution intended for topical ophthalmic use that functions as a mast cell stabilizer).
In addition, Brooks relayed that pulsed oral dexamethasone therapy is another option for some headshaking horses.
The short communication was published in the September 6th edition of The Veterinary Record.
Treatment for Ringworm
by: Jeffrey T. Berk, VMD
March 01, 2005, The Horse.com Newsletter
Q: I have consulted with three local veterinarians about the best way to treat ringworm. Each one gave me a different treatment recommendation. What is the most effective way to treat ringworm? Mary
A: Ringworm, which is not actually a worm but a fungal infection, is most likely a normal inhabitant of the skin. It can be introduced into the skin through abrasions or inflammation to create the crusty, flaky, round, hairless areas that are typically associated with the disease. There are many treatment options, which is why you have received the variety of recommendations. Your veterinarian will make a treatment plan that is most likely going to be safe and effective for your horse and also fit into your management situation.
Usually, the first part of treatment is to remove as much loose hair and crust as possible. This will decrease the number of fungal elements available that can re-infect the skin and spread to other objects, such as brushes, saddle pads, and blankets. Povidone iodine, used in frequent daily treatments, is a common agent used to disinfect the surface of the skin. Other agents may include chlorhexidine (Nolvasan), diluted bleach (watch out for irritation), and anti-fungal shampoos. In some cases, this may be all that is needed.
It takes several weeks to kill all of the fungal organisms, as they are living deep in the hair follicle. It is also important to disinfect grooming equipment and tack with povidone iodine or bleach to decrease the spread of the organism.
Some stubborn cases will benefit from treatment with a specific anti-fungal agent, such as gresiofulvin (Fulvacin), which can be added daily to the feed. In some cases it will be administered by your veterinarian in a bolus via a stomach tube. There are some health risks associated with gresiofulvin that include liver toxicity, so it is important to consider the general health of your horse before choosing the best treatment.
This can be a stubborn problem, so be diligent in the course and duration of treatment. There also can be an underlying cause for the ringworm infection, and a medical work-up, including a blood panel, might be needed. Working closely with your veterinarian will usually clear up the infection.
Deworming Keeps Horses Healthy from the Inside Out
Pfizer Animal Health recommends one of two deworming methods for regular deworming: Periodic Paste Deworming (Rotation is Key) and Continuous Deworming (Daily Plus). With periodic paste deworming you administer a paste dewormer every 6 to 8 weeks, rotating between chemical classes. The recommended products to use are STRONGID? C (pyrantel tartrate) Paste, ANTHELCIDE? EQ (oxibendazole) Paste and EQUIMAX? (ivermectin 1.87%/praziquantel 14.03%) Paste.
With continuous deworming, horses receive a small amount of granular dewormer in their feed every day, plus a combination paste dewormer twice a year to protect against tapeworms and bots. The recommended daily dewormer is STRONGID C Paste or the more concentrated STRONGID C 2X, and the recommended twice-yearly dewormer is EQUIMAX.
To learn more visit RotationIsKey.com or ask your veterinarian.
STRONGID and ANTHELCIDE EQ are registered trademarks of Pfizer Inc. EQUIMAX is a registered trademark of Virbac S.A. and is distributed by Pfizer Inc. ? 2008 Pfizer Inc. All rights reserved.
Thoroughbred Adoption Service Launched for FREE Horses
by: Kimberly S. Brown, Editor
November 01 2008, Article # 13006-The Horse.com
Thoroughbreds are great athletes, and they also are great pleasure and companion animals for those who love horses.
Bloodhorse.com and TheHorse.com are teaming up to bring Thoroughbreds in need of homes to the attention of hundreds of thousands of horse owners across the United States. Creating this database was the brainchild of Antony Beck of Gainesway Farm.
With the Thoroughbred Adoption Services, any registered Thoroughbred, of any age, is eligible to be placed on this database of FREE horses. The database will be housed on TheHorse.com and will be promoted in the Thoroughbred industry by The Blood-Horse and Bloodhorse.com and in the pleasure horse and sport horse industries by The Horse and TheHorse.com.
In these tough economic times some Thoroughbreds need to find other homes and careers. This database allows Thoroughbred owners, breeders, and trainers to place a description of a Thoroughbred in front of horse industry participants with the objective of finding a good home for that horse. Any transactions will be the responsibility of the owner of the horse, who will be contacted directly by those interested in adopting that horse.
If you--or someone you know--has a Thoroughbred in need of a new home, please visit TheHorse.com. Links to the database will be on the home page starting Friday, Oct. 31.
Or you can visit Add A Horse to add a horse or Horses Available to view horses seeking new homes.
We recommend anyone giving away a horse, whether to a private individual or a welfare/rescue organization, learn as much as possible about that person or group prior to giving the horse away. There have been unscrupulous individuals and groups who take horses under the pretense of giving them good homes, then sell them for slaughter. (See article "Rescue Highlights Danger of Free Horses".)
The article "Horse Rescue Organizations: Questions to Ask" offers some tips on making sure the person or group who takes your horse has good intentions.
There also are some very good organizations that are recognized throughout the Thoroughbred and horse industries as being legitimate places to donate your horses, especially the sound horses looking for other careers. The article "Options for Ex-Racehorses" will give you the names and contact information for some of these groups whether you are interested in donating or adopting a Thoroughbred. BloodHorse.com offers an online directory of welfare and rescue organizations, as does the Unwanted horse Coalition.
Please spread the word to help Thoroughbreds find new homes and careers.
Report: Government Must Revise Wild Horse Program
by: The Associated Press
November 11 2008, Article # 13066, thehorse.com
The U.S. Bureau of Land Management (BLM) needs to consider euthanizing wild horses or selling many of them to reduce spiraling costs of keeping them in long-term holding pens, said a government report Monday.
The report by the Government Accountability Office, the investigative arm of Congress, said costs of caring for wild horses have skyrocketed in recent years and likely will account for 74% of the program's overall budget this year, or more than $27 million.
Within its current budget, "BLM cannot afford to care for all the animals off the range, while at the same time manage wild horse and burro populations on the range," the report said.
The BLM determines how many wild horses can graze in various areas and rounds up the excess number to protect the herd, the range and other foraging animals. The horses are offered for adoption.
There are about 33,000 wild horses on the range in 10 Western states, half of those in Nevada. The BLM has set a target "appropriate management level" of horses at 27,000. About 30,000 more horses are in holding facilities.
Tom Gorey, a BLM spokesman in Washington, D.C., said the agency welcomed the findings.
"The GAO report correctly depicts the difficult situation that the BLM finds itself in with regard to maintaining unadopted or unsold animals in holding facilities," Gorey said in a written statement.
In late June, BLM Deputy Director Henri Bisson said the agency would consider euthanizing and selling horses to reduce costs.
The report noted the agency has authority to euthanize or sell large numbers of horses without restrictions but has not done that because of fear of outrage from the public or Congress.
Other options could be explored, the report said, including relocating infertile herds to areas outside original boundaries set by the 1971 Wild Horse and Burro Act, or giving tax breaks to large land owners willing to care for large numbers of animals.
Some of those measures, however, are outside the agency's authority and would require congressional approval.
The BLM has relied on adoption programs that require people who adopt the animals not to sell them for slaughter. The agency also keeps older animals or those deemed unadoptable in long-term facilities. Some live for 15 to 20 years in the pens.
Some advocates say horse populations are a result of years of mismanagement by the BLM. They also say horses are given short shrift on public lands because they compete with livestock for available forage.
Advocates could not be reached for immediate comment on the lengthy report, but they have said other alternatives need to be considered.
"There are better ways to deal with the problems BLM is facing," Lacy Dalton, president of the Let 'Em Run Foundation, said in July. Dalton says the government should build sanctuaries and give tax breaks to ranchers who let wild horses in their grazing areas.
"These horses are a beautiful symbol of this country, and I believe the public will not stand for their deaths. The public is willing to do what they can to prevent that," Dalton said.
Researchers Explore Reasons for 'Early' Return of Small Strongyles Following Treatment
by: Stacey Oke, DVM, MSc
November 11 2008
Research has shown that small strongyle eggs, apparent in feces, are returning sooner after treating horses with ivermectin (a commonly administered broad-spectrum anti-parasitic drug) than when the drug was first marketed.
According to parasitologist Eugene Lyons, PhD, and colleagues from the department of veterinary science at the University of Kentucky's Gluck Equine Research Center, this trend has been reported in many parts of the world. Researchers continue to study the extent and possible reasons for this "early" return.
Field studies performed in 2007 on horses on one farm revealed that parasite eggs in study horses' manure (eggs per gram, or EPGs) returned about twice as quickly after treatment with ivermectin compared to when the drug was first commercially available in the early 1980s. (Read more.)
In follow-up tests performed this year, Lyons evaluated the effect of ivermectin at the therapeutic dose rate of (200 µg/kg) in four yearling horses born and raised together on a farm in Central Kentucky. He wanted to determine the reason for the egg counts' swift return.
"In feces passed within six days post-treatment, 13 different species of adult small strongyles were identified," summarized Lyons. "On Day 6 post-treatment, almost 100% removal of adult small strongyles was noted; however, removal of fourth stage (L4) small strongyles was only 36-80%."
In the one horse assessed on Day 25 post-treatment, adult small strongyles were plentiful.
According to Lyons, "This suggests that the adult small strongyles found in the horse evaluated on Day 25 post-treatment are a result of the incomplete removal of the immature L4s by ivermectin, allowing these immature parasites to develop into adults and begin laying eggs by Day 25 post-treatment."
The rate of maturation of the L4s into egg-laying adult worms is faster than when ivermectin was first marketed. In effect, this means that the life cycle of the parasite has shortened.
While these results might appear outwardly discouraging, Lyons reminds the veterinary community that together, his results show that ivermectin in still highly effective against adult small strongyles and partially effective against the L4s.
Lyons noted that researchers need to conduct similar studies on other farms to determine if the same phenomenon occurs throughout the horse industry. Research in this field of study is important, considering that small strongyles have shown resistance to most commercial deworming products and because no new products effective against small strongyles are forthcoming on the market. Studies in Lyons' laboratory are ongoing.
The study, "Probable reason why small strongyle EPG counts are returning 'early' after ivermectin treatment of horses on a farm in Central Kentucky," is scheduled to be published in an upcoming edition of the journal Parasitology Research. The abstract is currently available on PubMed.
|All Topics Infectious Diseases
From African horse sickness to zoonotic diseases (those you and your horse can share), there are more than 35 infectious/contagious diseases that can affect your horse. Find out about treatment and prevention of diseases such as West Nile virus, equine protozoal myeloencephalitis (EPM), encephalitis, rabies, strangles, pneumonia, equine herpesvirus, botulism, anthrax, and many more.
Dealing with Emerging Infectious Diseases
by: Stacey Oke, DVM, MSc
March 05 2008, Article # 11438-thehorse.com
Scientists are becoming increasingly concerned about the marked and persistent development of emerging infectious diseases--infections that are new to a population or geographic area, have appeared more frequently, or have become more virulent (able to cause disease).
Within the past two decades, the list of emerging infectious diseases and pathogens of clinical relevance to the equine industry has expanded and now includes: the equine herpesvirus-1 neuropathogenic mutant; equine multi-nodular pulmonary fibrosis; Clostridium difficile; equine protozoal myeloencephalopathy (EPM), and; methicillin-resistant Staphylococcus aureus (MRSA), among others.
Within the North American equine populations, likely the best example of an emerging infectious disease is West Nile virus (WNV).
"Prior to 1999, WNV was not recognized in the United States," explained Josie Traub-Dargatz, DVM, MS, Dipl. ACVIM, professor of equine medicine at Colorado State University, "Now, the WNV equine vaccine is the most commonly administered vaccine among equine operations that vaccinate against one or more diseases, which illustrates a rapid and broad response by veterinarians and equine owners that were faced with an emerging disease."
Infectious diseases are on the rise, and horse owners and veterinarians are responding to this challenge by becoming increasingly cognizant of abnormal behaviors in horses. Owners, with the assistance of their veterinarians, possess the ability to recognize new diseases.
What has caused this surge in emerging infectious diseases?
According to Barbara Bischoff, DVM, veterinary analyst from the Centers for Emerging Issues at the USDA's Animal and Plant Health Inspection Service, a variety of factors are thought to contribute to the development of an emerging disease.
"In general, shifts in the environment-host-agent triad result in the opportunity for an emerging disease to develop," said Bischoff.
The most common causes of emerging infectious diseases include:
Climate change or other environmental changes that can potentially impact the life cycle of the vectors (e.g., insects and other animals);
Urban sprawl of humans and horses into geographic areas that are home to animals or insects that can transmit viruses, bacteria, or parasites;
Alterations in host factors such as immune capabilities of horses (perhaps via changes in management practices);
Globalization of humans and animals that provides unique opportunities to potentially spread disease; and
Changes in the agent (virus, bacterium, parasite) itself at a cellular level such as the shifting or drifting of genetic material.
"Because it is challenging to predict what the next emerging diseases might be, the best way to protect horses is to contain potentially contagious diseases via hygiene and isolation measures, until targeted intervention strategies (such as vaccination) are available," suggested Traub-Dargatz. "Other control measures could include insect or rodent management to control spread of infection, depending on the mode of transmission."
While it may not be possible to predict the next "big" infectious disease in horses, recent technological advances permit the relatively rapid development of diagnostic tests as well as vaccines, as evidenced by the rapid vaccine development subsequent to the WNV outbreak.
Emerging infectious diseases also have an obvious economic impact on the horse industry. For example, in 2002 WNV-associated costs in Colorado and Nebraska alone were $4 million; these included such factors as cost of treatment, loss of use, loss of horse, and cost of vaccinations.
"Nonetheless, beneficial impacts to the equine industry include an increased awareness of emerging diseases, increased biosecurity measures on the owner's part, an increased co-operation between owners and veterinarians in the face of new or abnormal clinical signs of disease, and an impressively rapid rate of developing diagnostic tests and safe, effective vaccines as we saw following the emergence of WNV," concluded Bischoff.
Form and Function of Joints
by: Les Sellnow
June 01 2001, Article # 36 , thehorse.com
There is a definite correlation between joint angle, hoof flight pattern, and weight bearing. One might even wax a bit poetic and declare that as the joint angles, so flies and lands the hoof. That's where the poetry ends, however, because if there are improper joint and/or hoof angles during weight bearing, there can be lameness problems.
There are three types of joints--fibrous, cartilaginous, and synovial. While all three are highly important, the synovial joints are more apt to affect hoof flight if they are out of alignment.
Fibrous joints are pretty much immovable and are united by fibrous tissue. Those fibrous joints are found in the skull and between the shafts of some long bones.
Cartilaginous joints have a bit more movement, but their range is still limited. Included in these types of joints are the pelvic and spinal joints.
The synovial joints are the most active in the horse's body and, as mentioned above, are the ones that will normally have a strong bearing on hoof flight pattern. One can say that these joints serve as the horse's ball bearings. They consist of two bone ends covered by articular cartilage. This cartilage is smooth and resilient, which allows for frictionless movement of the joint when properly lubricated with synovial fluid.
Joint stability is maintained by a fibrous joint capsule, which attaches to both bones, and collateral ligaments. The collateral ligaments are located on either side of most joints. They are important in maintaining stability in joints such as the fetlock, knee, elbow, hock, and stifle. Other ligaments surrounding the joint capsule also play a supporting role--a prime example involves the distal sesamoidean ligaments and suspensory ligaments that, together with the sesamoid bones, make up the suspensory apparatus and hold the fetlock in position.
Other ligaments within the joint, such as the cruciate ligaments, also help with stability. These ligaments provide important support.
While ball bearings are designed to provide frictionless movement in vehicles, they can only continue to do so if they are lubricated. It is the same with the joints. The joint capsule contains an inner lining known as the synovial membrane. Its function is to secrete synovial fluid, which lubricates the joint.
It becomes immediately obvious that a sophisticated structure like the joint needs proper alignment if it is to remain healthy. A joint that is not aligned correctly bears inappropriate strain throughout the entire structure. Not only is proper hoof flight altered by misalignment, but the potential for injury and disease from improper weight bearing is magnified.
Before discussing just how joint angle affects locomotion and weight bearing, let's take a quick look at the various movements that occur when a horse travels. Our tutor is Hilary M. Clayton, BVMS, PhD, MRCVS, holder of the Mary Anne McPhail Chair in Equine Sports Medicine at Michigan State University. Although she has spoken and written at great length on this subject, we will capsulize her work here.
The swing phase, when the horse's hoof is not in contact with the ground, does not result in great stress on poorly aligned joints. In the swing phase, the limb is first pulled forward, then pulled backward in the final movement prior to ground contact. "The forces on tendons and ligaments of the joints during the swing phase are very small," Clayton says.
Any damage usually occurs from misalignment trauma during the stance or weight-bearing phase, which describes that period when the hoof is in contact with the ground. The phase is divided into ground contact, impact, loading, and breakover.
Ground Contact--The first contact is either heel first, flat-footed, or toe first, depending on gait, speed, farriery, and/or lameness.
Impact Phase--The impact phase occupies the first 50 milliseconds (one-twentieth of a second) after the hoof contacts the ground. During this time, the limb undergoes rapid deceleration that causes a shock wave to travel up the horse's limb. Important shock absorbers at this point are the joints. During the impact phase, the bones receive their maximum amount of shock, so this is the phase when most bone and joint injuries occur.
Loading Phase--Loading and unloading occupy the period from the end of the impact phase until breakover. During this phase, forces are applied more gradually than during impact, and it is during this phase that ligaments and tendons are maximally loaded. Naturally, this is the phase when most soft tissue injuries occur.
Breakover--The breakover phase begins when the heels leave the ground and begin to rotate around the toe of the hoof, which is still in contact with the ground.
Aligning the Front End
Let's start with the front end, because this is where the horse carries 60-65% of its weight. As a result of this "heavier" front end, a horse is more apt to have joint problems in the front legs than in the rear.
If the hoof flight is to be straight and true, all parts of the moving leg must be aligned, beginning with the shoulder. When we look at a horse from in front, we should see a straight line down the forearm, through the knee, and into the pastern and hoof. The distance between the legs at the chest should be the same as the distance between the feet on the ground. Few horses have perfect conformation, and the amount of deviation has a strong bearing on hoof flight abnormality and the potential for injury and joint disease.
Proper alignment in the front end begins in the shoulder. What this means is that the slope of the shoulder should match the slope of the pastern and hoof, with forearm and cannon bones forming a straight line through the knee until reaching the pastern. This alignment has all of the bones fitting neatly together with properly aligned joints.
One of the most troublesome abnormalities in front limb joint conformation is toeing out. These horses have pastern, knee, and/or shoulder joints out of alignment, with the toes pointing out instead of forward. There's not a big problem as long as the horse remains still, but when he moves, particularly at the trot, the abnormality causes serious hoof flight problems. The hooves will wing inward, sometimes striking the opposite leg during the flight phase. Injury, accompanied by lameness, is often the result.
The reverse problem of toeing out is toeing in. Here the toes point inward instead of straight ahead during the ground contact phase. As the horse travels, the hooves will swing outward during the flight phase--this is known among horsemen as paddling. While this abnormal hoof flight pattern puts undue strain on joints, there is at least a bit of good news involved--the horse doesn't strike itself.
Base-wide horses (those that stand with their hooves farther apart than the legs are at the chest) often have narrow chests, and often toe out as well. Base-narrow horses stand with their hooves closer together than the legs are at the chest, and usually have wide chests. They tend to toe in.
The pasterns are key shock-absorbing joints, and as a result must be strong, yet pliable. The pastern is made up of two bones between the fetlock joint and the hoof, and the joint between those two bones. Long pasterns tend to have these two bones longer than normal, and the pasterns tend to drop more horizontally especially during high-stress disciplines such as racing and jumping. This increased range of motion can put more stress on the suspensory apparatus.
Pasterns that are too short remain fairly upright even with high stress. This results in too much concussion traveling up the leg because these less flexible pasterns are less efficient shock absorbers.
Other joint alignment problems originate in the knee or carpal joint. One that was previously thought to be quite serious is bench knee. This means that the forearm and cannon bone are not properly aligned. The bench-kneed horse will have the forearm entering the knee on the inside or medial aspect, while the cannon bone below the knee joint will exit on the outside or lateral aspect. Though it has commonly been thought that bench knees put a horse at serious risk for injury especially in high-stress disciplines, recent research suggests that this might not be the case.
Two other conditions of the knee joint that can alter normal hoof flight and weight bearing and raise the injury potential are being over at the knee (with the forearm ahead of the cannon bone viewed from the side, also known as bucked knee), or being behind at the knee (the reverse of over at the knee, also called calf knee). Of the two, calf knee is the more serious because of the stress on tendons and ligaments that run down the back of the leg, and because of the predisposition to chip fractures from overextension of the joint.
Knees can be misaligned laterally or medially as well. These conditions are known as bow legs and knock knees, respectively. See the table on page 108 for more information on these.
Rear End Alignment
Deviations in joint angles of the rear limbs can also have a profound effect on hoof flight and weight bearing. As with the front end, we want to see proper alignment down through the bones and joints of the rear limbs.
When the joints of the hind limbs are not correctly aligned, the horse will often not be a good athlete because it is unable to make proper use of muscle power either in propelling itself forward or in putting on the brakes for a sliding stop (when it will have difficulty keeping the feet parallel).
One fairly common stance in horses is being base narrow; when the base-narrow horse is at rest, its rear hooves are closer together than its hocks and hip joints. Mild base-narrow conformation behind does not usually cause problems. If a base-narrow horse has a tendency to wing in, however, the horse might interfere and cut or bruise the opposite leg. The opposite condition, which is much less common, is being base-wide. This means that the hooves, when on the ground, are wider apart than the hocks and stifles.
In the hind limbs, toeing out is common and less of a problem than in the front end--in fact, a recent study found that roughly 70% of horses naturally toe out behind.
Joint abnormalities in rear legs can also influence the length of a horse's stride. Generally speaking, horses with more angulation to their joints can have a longer stride than horses with straighter joints, much like the actual length of a tightly coiled spring versus a loosely coiled one.
An example is the sickle-hocked horse, where the rear cannon bone is angled forward from a vertical line. Such a horse might be able to reach well under itself. Conversely, the horse that is straight behind--where there is very little angulation between the thigh bone (femur) and the tibia--will be unable to reach as far forward with the rear legs and show very little engagement of the hind limbs for collection.
Several hock misalignments can cause lameness problems as well; see the table on pages 110-111 for diagrams of, and stresses associated with, these problems.
Proper alignment in the lower limbs means that the slope of the pastern should be the same as or very similar to the slope of the foot so that the long pastern bone, short pastern bone, and coffin bone all fit smoothly and neatly together.
The problem involving improper joint alignment, with resultant alteration of hoof flight and weight bearing, is that very little can be done to correct the problem.
"By the time the horse is mature, the limb structures have adapted to the misalignment," Clayton says. "If the horse is still sound and performing well, alterations in foot balance should be made carefully if at all, because any change at this point may ruin the horse's adaptation to his problem."
Hoof trimming to encourage proper alignment can be done, but only during the very early formative stages in a foal, and must be approached with great skill and care.
Once the horse reaches maturity, what you see is what you get. By attempting corrective trimming at that stage, one is merely adding additional stress and pressure on the joint.
AAEP 2008: Deworming--To Rotate or Not to Rotate?
by: Christy West, TheHorse.com Webmaster
March 01 2009, Article # 13695
Rotational deworming--dosing horses with different classes of dewormers in rotation--is often recommended for controlling equine internal parasites. The theory is that by using all of the available effective deworming drug classes, we combine their benefits into a maximally effective program. However, some researchers say rotation isn't a good idea because it contributes to parasite resistance and will reduce the effectiveness of available deworming drugs.
At the 2008 American Association of Equine Practitioners convention, held Dec. 6-10 in San Diego, Calif., two different viewpoints on rotational deworming were presented. We've included both here so you can see the evidence for both sides and make your own choices.
Presentation 1: Evaluation of Anthelmintic Rotational Regimens on a Previously Documented Fenbendazole-Resistant Farm
Wade Nichols, PhD, a senior technical services specialist at Intervet/Schering-Plough Animal Health, presented the results of a multiyear Texas Tech University study evaluating the efficacy of various parasite control strategies in a closed herd with documented resistance to fenbendazole.
"Parasite resistance is a real area of concern worldwide," he began. "It was first reported in 1960, and the main problem (in horses) is cyathostomes (small strongyles). Currently there are no new deworming drug classes on the horizon, so it's important that we preserve the use of all of our current drug classes.
"This series of experiments was conducted due to the fact that there is virtually no data concerning the use of anthelmintic (deworming) strategies in the equine animal and their effects on anthelmintic resistance by parasites," he said.
The herd in question included 28 Quarter Horses of mixed gender and age (from weanlings to adult mares when the study began in September 2003). They were initially dewormed with fenbendazole (FBZ) every 90 days for 18 months, after which time cyathostome resistance was documented (as expected). Next, Experiment 1 evaluated the efficacy of three dose levels of FBZ: 5 mg/kg, 10 mg/kg, and the larvicidal dose of 50 mg/kg (10 mg/kg given daily for five days) given every 28 days. Fecal egg count reduction tests (FECRT) showed resistance at all doses for the entire 140-day experiment, with only about 80% fecal egg count reduction (FECR) at even the highest larvicidal initial dose (the 100% target means no eggs after treatment and, thus, few worms left alive). He also noted that resistance was easier to detect in younger horses (which have less natural exposure and immunity to parasites); this group had higher parasite loads before and after treatment than mature horses.
"Regardless of dosage level, there was still some resistance," Nichols summarized. "So we can't get rid of resistant parasites just by using more drug or using it more often."
After three months, Experiment 2 on the same horses (in re-randomized groups) compared the 50 mg/kg larvicidal FBZ dose to moxidectin (0.4 mg/kg) and ivermectin (200 mcg/kg). Moxidectin and ivermectin significantly outperformed FBZ, with FECRs of 99.9% and 98.7%, compared to 84.3% for FBZ. Again, age was a significant factor; adult horses had at least 98.7% FECR even with FBZ, while young horses' FECR was lower, especially with FBZ (only 69.9% FECR).
"The performances of moxidectin and ivermectin were not significantly different from each other, but both were significantly more effective than fenbendazole," Nichols reported.
After another three-month break, the entire Texas Tech farm's equine population went onto a fast quarterly rotational deworming program for Experiment 3 (pyrantel pamoate in June, ivermectin+praziquantel in September, fenbendazole at the larvicidal dose in December, and moxidectin in March).
"Mean FECR in the first year was 95.8% with pyrantel, 100% with ivermectin, 97.8% with fenbendazole, and 100% with moxidectin," Nichols reported. "The majority of horses in 2006 had no or negligible egg counts after every treatment, in contrast to very high loads before. So resistance to fenbendazole can be overcome or drastically reduced by rotation of other classes.
In yet another rotation experiment (Experiment 4) with a six time per year rotation (larvicidal fenbendazole in January, moxidectin in March, pyrantel pamoate in May, fenbendazole in June, moxidectin in September, and ivermectin+praziquantel in November) at the same facility, it was further demonstrated that the use of FBZ was effective when used twice in this rotation. All anthelmintics were effective in reducing FEC in the horses with any parasite burdens. The facility and most horses were basically clean by this point in time. In Experiment 4, this rotational program was implemented in combination with good management practices, including pasture rotation, planting annuals such as winter wheat, rotation of species within pastures, as well as quarantine and anthelmintic treatment of all new horses. Currently they're on Year 6 and parasite loads continue to be very negligible.
"Contrary to other reports, this series says you can go back to fenbendazole after prior resistance," he concluded. "There are limited (dewormer) classes available; we need to use all classes of anthelmintics (deworming drugs) to help preserve their efficacy."
Further, it was stressed that more field and clinical trials need to be conducted on farms and ranches where parasite resistance exists, and that there is an important need in the industry to test various theories of parasite control programs in varied environmental and management conditions.
Presentation 2: Rotation Creates Resistance
Cyprianna Swiderski, DVM, PhD, Dipl. ACVIM, assistant professor of veterinary medicine at Mississippi State University, discussed resistance in small strongyles. She stated that studies of anthelmintic resistance confirm that rotating dewormers without documenting that the drug being used is truly efficacious actually propagates resistance to all drugs in the program. "In such a scenario, the more effective drugs in the rotation mask resistance for a time," she said. "The most powerful way to minimize anthelmintic resistance is to minimize the frequency of anthelmintic use, and therefore reduce the selection pressure placed upon parasites to develop resistance. It is now clear that anthelmintic use can be minimized by capitalizing on seasonal changes in the prevalence of small strongyles as well as differences in parasite immunity among individual horses."
Swiderski presented a review of literature on equine parasite control and recommended new paradigms for small strongyle control in adult horses based on several concepts.
First, the concept of zero tolerance for small strongyles should be abandoned, as some degree of parasitism is necessary to stimulate an immune response. Horses that lack such exposure tend to have more severe health problems when parasite exposure eventually occurs, which is assured in an animal whose optimal health depends upon grazing.
Preserving refugia--parasite populations that are still susceptible to common deworming drugs--is of paramount importance. Refugia are critical because they lack resistance genes. This "resistance-free" population effectively dilutes the pool of resistance genes contributed by anthelmintic-resistant parasites.
Anthelmintic overuse depletes refugia to a greater degree than it depletes the resistant worm population, which accelerates the development of resistance. Thus, we should minimize anthelmintic use wherever possible, such as by strategically deworming horses only when infective small strongyle larvae are plentiful on pasture (spring to fall in cooler regions, and fall to spring in warmer regions).
Individual horses vary greatly in their susceptibility to internal parasites; some limit infection almost entirely even without deworming drugs, while others carry very high parasite loads even with regular deworming (Swiderski cited reports that found approximately 35% of horses account for 85% of pasture contamination). Thus, we can also reduce anthelmintic use by only deworming the horses that really need it.
Fecal egg counts are used to identify individuals needing anthelmintic therapy. Current recommendations are to deworm horses with at least 150-300 parasite eggs per gram (epg) of feces. Horses managed with this threshold for treatment have not shown ill thrift or an increase in colic. (More information on FEC testing, including how to do it
Anthelmintic class (determined active by the ingredient in the dewormer) influences the interval between deworming times (or FEC testing to determine if deworming is necessary), because the time it takes for worms to reinfect horses and produce eggs that are detectable in the feces (egg reappearance period, ERP) after deworming varies by anthelmintic class. When you are identifying horses for deworming treatment, use FEC tests done after the previous anthelmintic's efficacy has completely waned. Your veterinarian can help you determine how long this takes for your deworming program and can help interpret your FEC tests to see if resistance is appearing (for example, if the ERP is shortening). Typical ERPs for common dewormers are as follows: eight weeks for ivermectin, 12 weeks for moxidectin, four to six weeks for pyrantel, and four weeks for benzimidazoles.
Anthelmintics are not the only control measures for internal parasites, nor are they even the most effective ones. For example, removing feces from the environment every few days can be even more effective than deworming. Consider that once they leave the horse in feces, small strongyles must live outside the horse for a few days (depending on the temperature) before they can reinfect him or infect other horses. Thus, removing feces from the environment every few days ensures that only noninfective larvae are available on pasture to be eaten. This practice also increases the grazing area as much as 50%, as it removes the manure piles horses tend to avoid when grazing. This technique should be employed to reduce the need for deworming drugs.
Though small strongyles are the major parasite concern of the adult horse, they're not the only ones. Anthelmintic drugs should be selected based on the parasites found on the premises. For example, macrocyclic lactones such as ivermectin/moxidectin are critical for controlling large strongyles and Gasterophilus (bots), while praziquantel is necessary for controlling Anoplocephala (tapeworms).
The new paradigm for parasite control Swiderski recommended relies on three basic principles: Preserving refugia, deworming only those horses responsible for significant pasture contamination, and restricting anthelmintic therapy to seasons in which horses can become infected from pasture.
"Preventing anthelmintic resistance will require a more integral role for veterinarians in the planning and monitoring of anthelmintic therapy," she concluded. "We must stop looking at deworming as a formula and start recognizing that parasites are living, changing creatures. We need to employ strategies that can change since the parasites themselves can. We can establish guidelines, but we have to be flexible and always look for the worms to change."
Despite the costs of routine FEC tests, she noted that this approach has been proven effective in controlling both cost and parasites.
Points of Agreement
Regardless of their positions on anthelmintic rotation, Swiderski and Nichols agree that sound management practices should be an integral part of equine parasite control programs. Several recommended practices include the following:
Keep pens and pastures as free of feces as possible.
Swiderski recommends the following strategy for new arrivals to the herd: If a horse will be staying less than six weeks, deworm him with ivermectin because it takes six to eight weeks for eggs to reappear in the feces after using this drug, and resistance is rare. If a horse will be staying six weeks or longer, quarantine him and use high-dose fenbendazole to kill encysted small strongyle larvae, followed by ivermectin or moxidectin after two weeks. Release him from quarantine if comparisons of FEC testing from before and two weeks after deworming confirm appropriate reduction in egg counts (at least 80-90% FECR for all nonmacrocyclic lactones, and greater than 98% for the macrocylic lactones).
Swiderski also recommended singling out horses with high fecal egg counts at the beginning of the deworming season (>500 epg) for treatment with either moxidectin or larvicidal fenbendazole therapy (10 mg/kg once daily for five days), because these individuals tend to mount poor immune responses to small strongyles and harbor large numbers of encysted small strongyle larvae. These are also the individuals primarily responsible for contaminating pastures with parasites.
Avoid ground feeding.
Don't overcrowd pastures (avoids forcing horses to graze close to infected manure piles, where worms are usually plentiful) or spread manure on them.
Disc pastures only when climatic conditions (hot summer temperatures) will kill eggs and when pastures can be left unoccupied for two weeks in warm Southern climates or four weeks in cooler Northern climates. Pastures should not be harrowed after Oct. 1 in the United States because parasite larvae dispersed by harrowing will not undergo the climate extremes required to kill them.
Rotate livestock species in pastures when possible.
Leave pastures vacant for at least two months during the warm season when possible, or allow horses to graze fields that have recently produced hay.
Use scales/weight tapes to prevent inaccurate horse weight estimation and, thereby, underdosing when anthelmintics are used.
Run FEC and FECR tests; as Nichols commented, "If you can't measure what you're doing, you can't measure improvement."
Link Between Equine Diet and Behavior Explored
by: Liz Brown
April 16 2009, Article # 13977 -The Horse.com
Diet and stable management play a major role in horse behavior, according to researchers from the University of Bristol.
"There is a growing body of evidence to suggest that the more you can mimic the almost continuous natural grazing behavior of horses in the wild, the better," said study co-author Becky Hothersall, Phd, a researcher studying Equine Learning and Cognition at the University's School of Veterinary Science.
The authors found horses fed more hay displayed generally quieter behavior, and fewer stereotypic behaviors (such as cribbing or weaving), compared to horses fed infrequent and large high-starch meals.
"More time spent eating less nutrient-rich food is likely to fulfill your horse's instincts to forage, and may reduce digestive problems or blood sugar fluctuations associated with large meals," Hothersall said.
The study noted that after a horse ingests a large, starchy meal, "the higher proportion of dry matter in the stomach contents slows the mixing of feed and gastric juice ... and can result in discomfort and even gastric colic."
The authors noted some researchers believe cribbing might be a physiological response to help calm gastric upset, and that certain horses might be predisposed to this behavior.
Hothersall said stereotypic behavior is virtually unknown in the wild and suggests increasing turnout and social contact with other horses as a means to possibly prevent such behaviors. As well, the authors suggest using an automatic, timed feeding device to release smaller grain meals at more frequent intervals, as this may reduce some of these behaviors.
Hothersall said more research is needed to understand exactly how diet and management practices influence behavior.
"More studies that begin before stereotypies do are needed to get a better idea of what management, temperament, or physiological factors predispose a horse to developing stereotypies," she said. "When this is understood, we have a more realistic hope of preventing them."
The study, "Role of diet and feeding in normal and stereotypic behaviors in horses," was published in the April 2009 Veterinary Clinics of North America: Equine Practice
Researchers Evaluate Steps for Diagnosing Cushing's Disease
by: Stacey Oke, DVM, MSc
June 08 2011, Article # 18360
An earlier diagnosis for a horse often means a better prognosis for his recovery, but the reality with equine Cushing's disease has been that clinical signs are abundant before the diagnostic process begins. A team of researchers recently determined what they believe to be the ideal first step for diagnosing PPID early, however, and this could allow affected horses to receive treatment sooner and slow the progression of the debilitating disease.
The disease is caused by an enlargement of the pars intermedia of the pituitary gland, which is the central part of the pituitary gland located at the base of the brain. When the gland becomes enlarged, it secretes excessive amounts of adrenocorticotropin hormone (ACTH) which increases adrenal gland cortisol (stress hormone) secretion. A common condition in older horses, clinical signs include a long hair coat, delayed shedding of the winter hair coat, loss of muscle mass, increased drinking and urination, a pot-bellied appearance, and an increased susceptibility to infections. If left untreated, Cushing's horses generally experience chronic bouts of disease, a decline in health and comfort, and reduced quality of life.
There are several tests currently available to aid veterinarians in diagnosing PPID, measuring:
Resting adrenocorticotropic hormone levels (and keeping in mind that ACTH concentrations can be variable in an individual horse with pituitary dysfunction, it is important to get at least two blood samples);
Suppression of cortisol from dexamethasone administration (the dexamethasone suppression test); and
The change in ACTH concentrations in the blood after administering thyrotropin-releasing hormone (the TRH response test) to the horse.
However, veterinarians report that alternative tests for equine Cushing's are needed, particularly to diagnose the disease prior to the onset of potentially life-threatening conditions, such as laminitis. In an attempt to find a better PPID diagnostic method, Jill Beech, VMD, Dipl. ACVIM, of the Department of Clinical Studies at the New Bolton Center in Pennsylvania, and colleagues compared the ACTH responses in the TRH test to those in a domperidone response test. (Domperidone is the substance that stilumates secretion of ACTH.)
"We also... compared the a-melanocyte-stimulating hormone (aMSH) response with ACTH response to TRH administration, as some research has suggested that measuring the former should be more accurate for diagnosing PPID," said Beech. "aMSH is produced by the pituitary gland like ACTH but is more specific for the pars intermedia."
Key findings of the study were:
The authors' findings indicate that measuring ACTH from several basal (resting) blood samples is the first logical step for diagnosing PPID.
"If the ACTH levels are very high and other potential influential factors have been eliminated from consideration, this is very good evidence that the horse or pony has PPID," advised Beech. Levels of ACHT and aMSH have been documented to vary seasonally, however the reason behind the difference remains unclear.
Understanding Equine Medications is your A-Z guide to learning more about generic and brand-name pharmaceuticals, possible side effects and precautions, and proper dosage.
The authors caution, however, that even if the concentrations on testing are normal, the horse might still have the condition, so he should be kept under close observation for further signs of the disease. In this case the authors attest that the ACTH response to TRH administration appears to be the best test for diagnosing the condition.
According to Beech, "if the horse shows classical signs of PPID, endocrine testing is probably not necessary for making the diagnosis," but it's a better scenario to diagnose the condition before it advances to a less treatable stage.
The study, "a-melanocyte-stimulating hormone and adrenocorticotropin concentrations in response to thyrotropin-releasing hormone and comparison with adrenocorticotropin concentration after domperidone administration in healthy horses and horses with pituitary pars intermedia dysfunction," was published in the May 15, 2011 edition of the Journal of the American Veterinary Medical Association.
HOW VETERINARIANS AND HORSE OWNERS CAN COMBAT THE AFTERMATH OF STRESS
You know the drill: you load your healthy horse into a trailer and head off to a show, a race, a breeding appointment, etc., and the next thing you know, your horse is sick.
That's because stress-inducing events may reactivate the equine herpesvirus Types 1 and 4 (EHV-1 and EHV-4), which the majority of horses can carry latently in their bodies. The result can be an upper respiratory tract illness, or worse. Not to mention lost competition time, expensive veterinary visits and the possibility of infecting other horses.
Your veterinarian has the answer: ZYLEXIS. Given in a series of three injections - two before and one after the stressful event - ZYLEXIS stimulates the horse's immune system, resulting in less nasal discharge, fewer respiratory symptoms and for fewer days.1
Now that's a load off you and your horse. See your veterinarian for more information.
1 Data on file, Study Report No. Equine 1-98, Pfizer Inc.
Zylexis is a trademark of Pfizer Inc.
© 2007 Pfizer Inc. All rights reserved.
Diagnosing Insulin Resistance: Q&A with Researchers
by: Kathryn Watts, BS
August 28 2008, Article # 12588 -thehorse.com
Over the past few years researchers have described a strong association between insulin resistance and laminitis in equines. They are working now on defining standard testing protocols and interpretations to identify horses at highest risk for laminitis. Many questions remain unanswered. How should insulin resistance be defined and diagnosed? How do researchers interpret test results? Can blood tests alone determine the risk of our horse or pony to get laminitis? Until they have more solid science to configure a standard definition of equine insulin resistance, those attempting to define it might find themselves in the same predicament as the proverbial group of blind men describing an elephant.
A study in the United States showed that laminitis affected 2% of all horses, with the incidence going up to 5% in spring, which is when grass sugars peak. The ability to identify high risk animals before laminitis strikes is essential, as this can allow caretakers to implement appropriate management practices to prevent it. Sinking or rotation of the coffin bone requires treatment and rehabilitation regimes that can be difficult, long, expensive, and emotionally draining. Even then, the treatments often fail. But how do we identify the high-risk animal? Of course any horse that has had a brush with laminitis should have tests for underlying endocrine problems, but certain physical characteristics should lead proactive owners to test for insulin resistance.
A "cresty neck" is the classic sign of insulin resistance, and researchers note a solid correlation between neck circumference and the condition. Horses that gain weight much more quickly, often described as "blowing up on grass" than their herdmates under similar management, might be candidates for testing, especially if they also exhibit signs of foot tenderness. Additional signs are rings on the hoof wall, or a stretched white line with blood specks when the foot is viewed from the bottom, both which could be indications of a previous mild case of laminitis.
Not all fat horses are insulin resistant (IR), and not all IR horses are fat. Typical body scoring parameters might not apply to some IR horses. Even horses with ribs showing might have insulin resistance. Even when they maintain proper body weight with dietary restriction, IR equines might still display subtle signs of regional adiposity, with fat pads that form behind the shoulder, around the tailhead, over the loin, or as a slight crest with a dip in front of the withers. These abnormal fat deposits might be lumpy or dimpled in appearance.
In a clinical setting, dynamic tests are considered the most accurate for diagnosis of impaired endocrine function. The combined glucose-insulin tolerance (CGIT) test measures the horse's response to a standard dose of glucose and insulin over several hours with multiple blood draws. Insulin resistant horses maintain high glucose and insulin levels longer than normal. Compared to tests based on a single blood sample, the CGIT is not as practical in the field, is more expensive, and if the horse is stressed by being in a stall away from home, it might affect the results. Therefore, it becomes important to derive as much information as possible from diagnostic tests that can be done with a single blood draw. Baseline insulin and glucose levels can be very informative.
Although the scientific community is far from having all the answers, two leading researchers have shared their expertise and opinions about how insulin resistance should be diagnosed.
Nicholas Frank, DVM, PhD, Dipl. ACVIM, an associate professor of large animal internal medicine at the University of Tennessee is conducting studies on a herd of insulin resistant horses with chronic laminitis. Horse owners managing laminitic horses can relate to his description of this herd as "trying to keep a flotilla of leaky ships afloat."
Ray Geor, BVSc, MVSc, PhD, Dipl. ACVIM, director of research at Virginia Tech's Middleburg Agricultural Research and Extension Center was part of the team who first described pre-laminitic metabolic syndrome in a herd of Welsh and Dartmoor ponies. Ponies at greatest risk for laminitis could be identified by blood tests for insulin, glucose, and triglycerides even before their first laminitis episode was triggered by spring pasture.
Question: What is your stand on fasting before blood draw for insulin and glucose? Some say that the stress of fasting could alter test results, especially if the horse is used to having free access to hay.
Dr. Frank: There are two approaches that I recommend with respect to feeding and fasting before blood draws. If the horse remains calm when deprived of feed for a few hours, I recommend feeding a flake of hay at 10 p.m. the night before and then collecting blood the next morning. However, we have also have found that some of the obese horses that we test become very agitated when feed is withheld. This causes stress, which affects test results because stress hormones such as cortisol and epinephrine cause temporary insulin resistance. Stress during testing can, therefore, lead to the misdiagnosis of insulin resistance. We have not detected any short-term effects of feeding hay on resting blood glucose and insulin concentrations, so we recommend that the horse be fed hay as normal before and during testing. It is possible that feeding hay that is rich in sugars within the 12-hour period before testing could raise concentrations above fasting levels, but we choose to accept this possibility over the known complication of stress. Grain should never be fed in the 12 hours before testing.
Dr. Geor: Standardization of the sampling protocol is extremely important, particularly how the horse is fed during the 12-hour period prior to blood draw. Our studies have shown that the sugars in pasture forage can markedly impact blood insulin (and, to a lesser extent, glucose) levels, potentially leading to a false diagnosis of insulin resistance. This does not seem to be a problem when hay is fed, even when the nonstructural carbohydrate content is moderately high. Therefore, we recommend that horses are removed from pasture--to a stall or drylot-for about 12 hours prior to blood draw. No grain should be fed during this period but hay should be offered. Fasting is not a normal state for the horse and may cause stress that affects test results.
Are there times when testing for insulin and glucose is not appropriate?
Dr. Frank: The most important consideration before collecting blood is whether the horse is experiencing pain as a result of laminitis. If this is the case, stress hormones are likely to be causing insulin resistance and serum insulin levels will be high. It is, therefore, very important to wait until the pain of laminitis has subsided before testing horses for IR.
If a horse is tested on a hay-only diet, and blood levels of insulin or glucose are above the "normal" range of the testing laboratory, a positive diagnosis of hyperinsulinemia or hyperglycemia can be made. But what does "normal" mean? Different labs have different ranges for normal. The analytical procedure for insulin in horses is not standardized and, therefore, may differ from one lab to another. It is, therefore, important to select a laboratory that often measures insulin levels in horse blood and remain with the same lab to assess progress in an individual case.
Might a horse still be considered IR if test results for insulin are within the lab's "normal" range?
Dr. Frank: For our laboratory we consider a blood insulin level > 20 µU/mL (microunits per milliliter) to be suggestive of IR and > 30 µU/mL defines hyperinsulinemia and therefore insulin resistance. We occasionally encounter horses with normal insulin levels and abnormal intravenous combined glucose-insulin test (CGIT) results. These patients suffer from mild insulin resistance that is likely to be exacerbated by pasture grazing, grain feeding, or seasonal changes.
Dr. Geor: I do not place much faith in the reference ranges developed by some of the commercial labs. These ranges are sometimes based on very few animals. In general, I go with >20 µU/mL as suspicious and >30 µU/mL as more convincing evidence of hyperinsulinemia and an IR problem providing the sample was collected in an appropriate manner.
Please define "compensated" and "uncompensated" insulin resistance.
Dr. Geor: Compensated insulin resistance implies that glucose values are being regulated within the norm. There is insulin resistance but increased insulin secretion and, therefore, higher circulating insulin "overcomes" the insulin resistance, such that glucose is taken up by the cells and blood glucose is within reference limits. Uncompensated insulin resistance is when high insulin fails to overcome the resistance and blood glucose values rise above normal.
Do glucose levels alone give us useful information? What level defines hyperglycemia?
Dr. Frank: Most horses with insulin resistance are able to maintain blood glucose concentrations within reference range, so normal blood sugar levels are not diagnostic. Levels are rarely higher than the reference range (hyperglycemia), and when this problem is detected, it is cause for greater concern. Hyperglycemia often indicates that insulin resistance has been going on for long time and is seen in older patients. When hyperglycemia is detected, the veterinarian should test the patient for pituitary Cushing's disease because our research group has detected hyperglycemia in horses and ponies with this hormonal problem. I use 100 mg/dL, (milligrams per deciliter) but this is a somewhat arbitrary cut-off.
Dr. Geor: In the context of evaluating insulin resistance, it is necessary to evaluate both glucose and insulin, e.g., to differentiate compensated versus uncompensated insulin resistance. Blood glucose concentrations tend to rise very quickly in response to pain (e.g. due to current laminitis) or stress, so these factors need to be taken into consideration when interpreting blood glucose values. In general, a glucose value <100 mg/dl can be regarded as okay. Cushing's disease can result in increased glucose concentrations, so a finding of hyperglycemia (>100 mg/dl) in a horse or pony without evidence of current laminitis should prompt the veterinarian to test for this problem.
Might glucose: insulin ratios give us more information?
Dr. Frank: Although blood glucose levels usually remain within reference range, they may be higher than they would be if the horse were healthy. This is one reason for calculating the glucose to insulin (G:I) ratio. Unfortunately there are several problems with measuring blood glucose levels in horses. First, blood glucose levels quickly increase in the stressed horse, even within a few minutes. On the other hand, blood glucose levels decrease if the blood sample is handled improperly. Delaying the time between collection and centrifugation causes levels to decrease, particularly if the sample cannot be refrigerated. Finally, the major problem with the G:I ratio is that it does not account for differences between laboratories with respect to the insulin assay used. Glucose assays are very consistent between laboratories, but insulin values vary because different laboratories use different assays. If only insulin values are used to diagnose insulin resistance, results can be interpreted using the reference range provided by the laboratory. This reference range will have been adjusted up or down according to the assay used. However, you cannot account for differences in reference ranges when the G:I ratio is used, so horses look better or worse, depending upon the laboratory used.
Dr. Geor: For the reasons elaborated on by Dr. Frank, we do not use the glucose:insulin ratio for diagnosis of insulin resistance. Related to this question, there has been interest in the use of other proxy markers of insulin resistance based on measurements of glucose and insulin. The group at Virginia Tech developed proxy markers of insulin resistance (RISQI, calculated from blood insulin) and insulin secretory response (MIRG, modified insulin to glucose ratio) and used these to evaluate predisposition to laminitis in a herd of Welsh and Dartmoor ponies. Ponies with a history of laminitis were more insulin resistant as indicated by lower RISQI and higher MIRG compared with the ponies that were never laminitic. However, it must be stressed that the cutoff values used to separate the two groups should not be used for clinical diagnosis of insulin resistance in other populations of horses or ponies. For example, the RISQI cutoff represented an insulin value of 11-12 µU/mL--a value well below our clinically used cutoff for diagnosis of hyperinsulinemia.
Might a horse be considered IR based on a low G: I ratio even if the individual numbers are within normal range?
Dr. Geor: No, this would seem to be stretch and, in my view, will result in gross over diagnosis of insulin resistance.
Dr. Frank: The G:I ratio is used by some veterinarians to diagnose and characterize insulin resistance in horses. This value can be calculated by dividing the glucose concentration in mg/dL by the insulin concentration in µU/mL (same as mU/L). Glucose concentrations measured in mmol/L (millimoles per liter) must be multiplied by 18 to convert to mg/dL (milligrams per deciliter) and insulin concentrations reported in pmol/L must be divided by 7 to convert to µU/mL. For example, a horse with a blood glucose concentration of 80 mg/dL and serum insulin concentration of 5 µU/mL has a G:I ratio of 16.
Two cut-off values have been proposed for the interpretation of G:I ratios. The first is a value of 10, so a G:I ratio < 10 is supportive of IR. However, if we look at an example and set the blood glucose concentration at 90 mg/dL for the purposes of the discussion, a G:I ratio of 10 would be equivalent to a blood insulin level of 9 µU/mL, which is well within our reference range. A G:I value < 4.5 has also been proposed to diagnose insulin resistance, and this provides results that are more consistent with ours. If we go back to the example, the horse would have blood glucose and insulin concentrations of 90 mg/dL and 20 µU/mL, respectively. We suspect insulin resistance if the blood insulin concentration is > 20 µU/mL. Our research group does not use the G:I ratio because we have found that more variability is introduced when a value is based upon two variables, and each of these variables is potentially susceptible to sampling and handling error. Our group bases the diagnosis of insulin resistance on resting blood insulin concentrations, detection of hyperglycemia, or intravenous glucose and insulin challenge test results. I would not diagnose insulin resistance on the basis of a G:I ratio alone if blood insulin concentrations were not elevated.
Laboratory databases lump horse and ponies together. Is normal insulin for a pony the same as normal for a horse?
Dr. Frank: We currently do not distinguish between horses and ponies with respect to any of these parameters, although this work is in progress.
Dr. Geor: There is evidence that ponies are more insulin resistant than horses, potentially explaining their higher susceptibility to laminitis. Resting insulin values also tend to be higher in ponies compared to horses but we need more data before it will be possible to derive different cutoffs for diagnosis of insulin resistance.
Scientists hope research under way will someday help horse owners who suspect insulin resistance to get more accurate, standardized tests that can identify and define which horses require special management to avoid laminitis. The blood levels of insulin that consistently trigger changes in the foot are unknown. The mechanism for insulin induced laminitis is unknown. Scientists need to standardize the laboratory methods to quantify equine insulin, and they need to establish databases for "normal" insulin levels in populations with different genetic backgrounds.
Even if a horse is diagnosed unequivocally as being IR, that does not mean it will get laminitis. While insulin resistance as a background condition predisposes an animal to laminitis, avoiding the dietary and management practices that trigger the condition can prevent it from ever happening. This is why horse owners need to know.
Eliminating grain, increasing exercise, limiting access to high sugar pasture, and finding hays that test lower in sugar and starch can prevent laminitis even in animals that are predisposed.
Even if your horse or pony is borderline IR based on current definitions subject to revision, these practices generally can't hurt and might help a lot for a healthier future with a lot less worry.
Kathryn Watts, BS, is research director at Rocky Mountain Research & Consulting Inc.
California Declares WNV Emergency in Three Counties
by: The Associated Press
August 03 2007
Gov. Arnold Schwarzenegger declared a state of emergency Thursday in three California counties hit hard by the mosquito-borne West Nile virus, which has killed four people this year and appears to be spreading at a rapid clip.
The emergency declaration applies to Kern, Colusa, and San Joaquin counties, and will provide up to $1.35 million to help combat the spread of the virus, Schwarzenegger said.
West Nile is transmitted to humans through mosquito bites, and so far this year has infected three times more people than it did in the same period in 2006, he said.
The disease's epicenter thus far is Kern County, which has logged two-thirds of the state's 56 human West Nile cases this year including an 85-year-old Shafter man and a 96-year-old Bakersfield woman from Bakersfield who died last month. Health officials announced the state's third and fourth fatalities this week: two elderly residents of San Joaquin and Colusa counties.
Schwarzenegger met with Kern County mosquito control officials Thursday.
"Last year it was down, this year it has increased again," Schwarzenegger said. "The important thing is that we all go all out and we work together, the counties and the state, in order to get the job done and get rid of the virus."
Health officials recommend people avoid infection by staying inside at dawn and dusk, when mosquitoes are most active; wearing clothes that keep mosquitoes away from the skin; draining areas where mosquitoes can breed; and using insecticide with the chemical DEET.
In Sacramento County, authorities said Monday that West Nile had reached an epidemic rate there and had to be combated with a mass aerial-spraying campaign--often considered a last resort. More than 55,000 acres of urban neighborhoods north of the American River were scheduled to be sprayed.
Health officials in San Jose said Thursday that a Santa Clara County resident had become infected, in their first local case this year.
In Kern County, the new funds won't be enough to educate the public in time for the disease's high season in August and September, said Sen. Dean Florez, D-Shafter.
The state needs to provide a more consistent budget for eradication efforts in winter months, hire more vector control officers and coordinate surveillance efforts with real estate agents, who can provide updated information about vacant properties where standing water could provide the insects with a fertile breeding ground, he said.
"Next season could be quite possibly worse than this year unless we get a new infusion of money," Florez said.
Schwarzenegger said he was directing state agencies to take proactive measures, and that more funds could be made available if needed.
Click here for more on WNV in horses.
To track equine WNV cases reported to the USDA's National Animal Health Surveillance System in 2007 see http://nsu.aphis.usda.gov/nahss_web/faces/arbovirus_summary.jsp
Avocado Soybean Unsaponifiable (ASU) Extracts Earn a Passing Grade for Equine Osteoarthritis
by: Stacey Oke, DVM, MSc
July 30 2007
Avocado and soybean unsaponifiable (ASU) extracts--the fraction of oil that does not form soap after hydrolysis--are some of the newest joint products to grace the equine nutritional supplement shelves. The beneficial effects of ASU for horses with osteoarthritis were reported in a new study by David Frisbie, DVM, PhD and colleagues from the Gail Holmes Equine Orthopaedic Research Center at Colorado State University.
The researchers evaluated ASU in horses with experimentally-induced osteoarthritis. This clinical trial concluded that ASU significantly reduced the severity of joint damage and significantly increased the synthesis of cartilage glycosaminoglycans (i.e., the "building blocks" of articular cartilage) in joints with osteoarthritis, compared to horses treated with a placebo.
In this study, 16 horses with osteoarthritis were divided into two groups: eight horses received ASU extracts in molasses and eight received only molasses for 70 days. During the study, the horses were exercised on a treadmill and the researchers measured the horses' lameness, joint swelling, and various gross, microscopic, and biochemical parameters.
"While ASU did not decrease clinical signs of pain in horses with osteoarthritis, a disease-modifying effect was identified suggesting that oral administration of ASU can be useful in the management of horses with osteoarthritis," Frisbie reported.
Despite the need for further research to identify the exact cause of the observed beneficial effects of ASU, the ramifications of this landmark trial are potentially far-reaching. According to Frisbie, this is the first peer-reviewed, placebo-controlled study evaluating an oral nutritional supplement conducted in live horses with osteoarthritis.
The next step, suggested Frisbie, is to hold other supplement companies to higher standards to prove that their products also are effective.
The study, "Evaluation of avocado soybean unsaponifiable extracts for treatment of horses with experimentally induced osteoarthritis" was published in the June 2007 edition of the American Journal of Veterinary Research. Contributing researchers were Frisbie, Kawcak, DVM, PhD; McIlwraith BVSc, PhD; Werby DVM; and Park DVM, PhD.
Late Season Oats Can Reduce Autumn Hay Useby: The Ohio State University Extension
August 02 2007
Oats, traditionally grown in the spring as a grain crop, can also be planted in the summer as a late season forage, providing a feed alternative for horse owners and livestock producers short on hay or pasture. Based on five years of Ohio State University Extension research, oats planted in late July or early August can be grazed well into winter. "We have consistently experienced production of 4 to 7 tons of dry matter with an average of 18% protein. In some trials we were still getting 11% protein with oats grazed as late as March," said Stan Smith, an OSU Extension program assistant in Fairfield County. "The average production of hay harvested from perennial forages in Ohio is less than half of that. Without including land or harvest costs, the oats produced at that tonnage come at a total cost of less than $25 per ton, even at today's fertilizer prices.
Hay, by comparison, is presently valued at $60 to $70 or more per ton." Not all forages--or horses--are created equal. Ask your veterinarian if oats are appropriate for your horse.
With forage production in Ohio and surrounding states down this season due to a spring cold spell and ongoing dry conditions, producers are searching for alternative forages that are easy to establish and won't break the bank. Planting oats in the summer with the idea of grazing the crop was never thought of as an option in Ohio until Fairfield County Soil and Water Conservation District engineering technician Curt Stivison made a trip to the Heart of America Grazing Conference in 2001.
There, Stivison learned about late-planted oats research through the University of Illinois and decided to bring the concept back to Ohio. "I planted oats in my garden that summer. By Christmas the oats were still growing. At the time I didn't know of anyone else in Ohio growing late-planted oats," said Stivison. "In 2002, I moved the trials to a crop field, with similar results, and through collaboration with Stan Smith, we've been conducting late-planted oat trials ever since." Unlike spring oats, which are planted in March or April, head out in June and die soon after maturing, late season oats no longer produce seeds. As a result, all of the energy is put into leaf production (the source of dry matter protein). Oats will continue to grow until a significant freeze stops them, which in some cases can be as late as the end of December. Late-season oats can be seeded after wheat harvest, or interseeded with corn or soybeans. Although oats won't grow as tall in the presence of other crops, they can increase the overall quality of crop residues because of their high protein content, making corn fodder and soybean stubble more nutritional for livestock. Late-season oats can be grazed in the field, baled like hay, or ensiled. Smith said oats are a more attractive forage alternative than sorghum-sudangrass hybrids, cereal rye, or annual rye grass for a number of reasons: ·
When oats are planted after July 1, variety has no impact on forage yields. "We've used bin run seed, certified seed, treated seed, U.S. grown feed oats, and Canadian feed oats and found essentially no difference in the resulting forage production," said Smith. "That essentially means that producers can plant the cheapest oats they can find and still get good yields." By comparison, sorghum seed costs 2 to 3 times more. ·
Oats are a "scavenger" for nutrients and require little additional fertilizer. We've applied 18 to 50 units of supplemental nitrogen to July and early August planted oats and experienced similar yields with each rate," said Smith. "Fertilizer demand of sorghum-sudangrass hybrids is 3 to 4 times that." ·
Oats tend to tolerate dry conditions better than other alternatives. In fact, some of the best yields generated have been in July, August, and September when precipitation was below normal. ·
Oats reach maximum height faster. If a producer's primary need is to provide forage for this summer and winter, oats are a good option, as opposed to cereal rye or annual rye grass. Cereal rye and annual ryegrass, while both will grow in the fall, will not reach nearly the height that oats will before going into winter dormancy. "Cereal rye and annual rye grass are good crops if producers are looking for feed for next spring," said Smith. "Oats don't need to go dormant to elongate. They will reach maximum height and growth about 75 days after planting. Also, late-season oats do not need to be killed in order to plant a spring crop because they will eventually die over the winter. "Late-season oats are also a very forgiving crop, and tend to re-grow top growth if grazed before reaching maturity. "We used to think that fescue was the best crop you could grow as a winter forage, but that's turning out to not be the case," said Smith.
Researchers tested fescue along with oats and found that the protein content of oats was anywhere from 4 to 10% higher, depending on the month harvested. Stivison recently seeded his now dormant pastureland with late-season oats, in the hopes of adding to his forage production options. "Because of the hot weather, the cool-season grasses have shut down, and they won't come out of dormancy until it gets cooler. And even when they do break dormancy, there won't be enough grass available for grazing," said Stivison. "There's no reason to think that oats grown on dormant pastureland can't produce the same results we've seen in crop fields."
OSU Extension will be offering field days in August to provide livestock producers more information on forage options and the late-season oat trials. For more information on upcoming field days, visit the OSU Extension Beef Team web calendar at www.beef.osu.edu. For more information on the late-season oat trials, log on to www.fairfield.osu.edu/ag/graze/wntrgraz.htm.
Alabama Drought Getting Worse
by: The Associated Press
August 04, 2007
The latest survey from the U.S. Drought Monitor shows the drought is getting worse in Alabama despite recent heavy rains in some parts of the state.
The D-4 area representing exceptional drought conditions has grown from about 18% to cover more than 32% of the state. The driest areas run from northeast Alabama to about Montgomery.
Almost two-thirds of the state is covered by the second worst drought condition.
Climatologists also predict that the drought conditions will continue at least through October in north Alabama.
For more on managing horses in drought conditions see www.TheHorse.com/ViewArticle.aspx?ID=9721.
West Nile Virus Claims South Dakota Horse
by: The Associated Press
August 05, 2007
West Nile virus has killed a horse in Meade County, S. D.
This is South Dakota's first horse fatality from the disease since 2005, when three horses were struck by West Nile virus. There were no losses last year.
Sam Holland, DVM, South Dakota state veterinarian, said the 2-year-old Meade County filly had not been vaccinated against the disease.
Holland said vaccinations are at least partially responsible for the reduction in the number of reported cases since the equine form of the disease first appeared in the state in 2002.
Jockey Begins Year Suspension for Shocking Horse
by: The Associated Press
August 06, 2007
A jockey has begun serving a yearlong suspension for using an electronic buzzer on his Quarter Horse last year at Fairplex Park in Southern California.
Carlos Bautista began the suspension on July 24 after stewards at Los Alamitos racetrack were notified by Orange County Superior Court that a temporary restraining order had been lifted.
That allowed the California Horse Racing Board to enforce previous rulings for violations of its rules on possession of contraband and animal welfare.
The board announced Bautista's suspension Sunday in its weekly update of CHRB decisions.
The suspension followed a two-day hearing in October on a complaint filed by the CHRB alleging that Bautista used an electrical device to shock Royal Medallion during the pre-race warmup on Sept. 24, 2006.
Bautista was not accused of using the device, which can shock a horse into running faster, during the actual running of the race. Royal Medallion finished third.
Serbian Minister Checks on Lipizzaner Horses After Reports of Neglect
by: The Associated Press
August 02, 2007
A Serbian government minister Thursday visited a herd of famed Lipizzaner horses rescued from war, but now at the center of claims of starvation and neglect.
The horses were brought to north Serbia from Lipik, Croatia, in 1991 to protect them from the war that erupted after the break up of Yugoslavia.
The Lipizzaners are kept at a farm near Novi Sad, about 70 kilometers (42 miles) northwest of Belgrade, amid continued wrangling between Serbia and Croatia over ownership and the cost of care.
Earlier this week, animal protection groups and media reported that many of the horses were sick and on the verge of starvation.
Serbian Agriculture Minister Slobodan Milosavljevic visited the farm Thursday with vets to examine the horses. "I am no expert to judge their condition, but they seem in a decent state," he told reporters.
The Beta news agency quoted veterinarians as saying they had examined 74 horses and all were healthy.
However, the agency also quoted unnamed neighbors claiming the farm owner put up a "show" for the minister and that horses in bad condition had been hidden.
Milosavljevic said he would soon meet his Croatian counterpart Petar Cobankovic to try to resolve the dispute over the horses.
"We have to determine how they came here, how they were kept, what their present condition is and what should be done to solve the problem," he said.
The farm owner has demanded €300,000 ($410,000) in compensation for the horses' care but Croatia has refused to pay. Serbian authorities in the past have said the matter is to be resolved between the farm and the Croatian government.
Horse Quarantine, Inspection Nixed from Bill
by: Tom LaMarra
August 03, 2007
Weeks of lobbying by the horse industry were successful the evening of Aug. 2, when the United States House of Representatives voted overwhelmingly to remove from the Agriculture Appropriations Act language that could have stymied transportation of horses by halting funding for inspections.
The House voted 237-18 to strike the language, which would have prohibited the federal Animal and Plant Health Inspection Service from performing horse health monitoring and regulatory work. That would have impacted quarantine facilities and stopped the import and export of horses.
Some of the language used in the Agriculture Appropriations Act would have impacted quarantine facilities and stopped the import and export of horses.
Industry groups led by the National Thoroughbred Racing Association (NTRA) and the American Horse Council (AHC) urged the House to remove the language. House members reportedly received more than 100 phone calls and numerous email messages on the issue.
"A lot of people worked on this," AHC President Jay Hickey said. "We clearly got the House's attention."
Keith Chamblin, an NTRA spokesman, said the organization was "very pleased the House responded to the industry's concerns." The stricken language would have had far-reaching negative consequences for all equine disciplines, he added, calling the bill as originally drafted "a poor piece of legislation."
The Bush administration opposed the language that would have prohibited APHIS inspections. In a July 31 policy statement, it also expressed concern over potential withholding of funding for the National Animal Identification System, a voluntary program involving the equine industry.
The statement said the White House "strongly opposes" the full Agriculture Appropriations Act, which exceeds President Bush's request for funding by almost $1 billion. Combined with other fiscal year 2008 appropriations bills, it said, the bill calls for "an irresponsible and excess level of spending and includes other objectionable provisions."
Meanwhile, representatives John Spratt Jr. of South Carolina, Nick Rahall of West Virginia, and Ben Chandler and Ed Whitfield of Kentucky succeeded in inserting a provision in the measure to ban funding for federal officials who inspect horses bound for slaughterhouses. The United States Department of Agriculture has been charging a fee for such inspections, but a federal appeals court is determining the legality of that practice.
A motion to strike the amendment failed during the Aug. 2 debate on the bill.
"With anti-slaughter laws in Illinois and Texas, and now with this anti-slaughter language in a major spending bill in Congress, the writing is on the wall for the Belgian-owned slaughter plants in the United States," Wayne Pacelle, president and chief executive officer of the Humane Society of the United States, said in an Aug. 3 release. "The American people and their elected representatives want an end to horse slaughter -- not later, but right now."
(Originally published at www.BloodHorse.com.)
Foot and Mouth Disease: Restrictions on U.K. Horse Trainers Relaxed
by: Mark Popham
August 13, 2007
The movement of horses to and from the United Kingdom hasn't been affected by the recent small outbreak of foot and mouth disease at two farms in Surrey in southern England. Providing the correct certification has been completed, overseas-trained runners can continue to compete in races in Great Britain.
Restrictions placed on certain trainers in the affected area, imposed following the outbreak, were relaxed as of Aug. 13.
The stables that fell within a 10-kilometer surveillance zone, near the two farms where the disease was found, had been warned by the British Horseracing Authority, under guidance from the Department for Environment, Food, and Rural Affairs (DEFRA), that they wouldn't be able to ship horses to any race meets at home or abroad. However, with authorities believing the disease to be contained, trainers in the surveillance zone are now free to run their horses, providing they carry out the necessary biosecurity measures when transporting them to the racecourse.
Restrictions on trainers within the current three-kilometer protection zones in Surrey, remain in place. Although horses cannot be infected by foot and mouth disease, they can carry the virus on their hooves, skin, hair, and possibly in their nasal passages.
A serious outbreak of foot and mouth disease in the United Kingdom in 2001 devastated the farming community. It led to more than seven million animals being culled and cost the agricultural industry an estimated £8 billion ($16 billion). The 2001 Cheltenham Festival, the highest profile race meet for steeplechase horses in Great Britain, had to be abandoned following the 2001 outbreak.
It is thought the source of the latest outbreak was the Institute for Animal Health's Pirbright laboratory site in Surrey, used by vaccine manufacturer Merial.
(Originally published at www.BloodHorse.com.)
Arabian Horse Quotes
The Arabian stallion is magnificent, and the mare quite glamorous, but the airy-fairy foal is so delicate and fawn-like, he steals your heart away!
- Gladys Brown Edwards, "Know the Arabian Horse"
The wind of heaven is that which blows between a horse's ears. -Arabian proverb
Statements that Arabians are "never parti-color" are wrong, attributed to lack of historical knowledge and refusal to believe very conspicious evidence.
- Gladys Brown Edwards, "Know the Arabian Horse"
My Beautiful! My beautiful! that standest meekly by With thy proudly-arch'd and glossy neck, and dark and fiery eye, Fret not to roam the desert now, with all thy winged speed; I may not mount on thee again--thou'rt sold, my Arab steed! - Caroline Norton, (1808-1877) An Arab's Farewell to His Steed
The following are excerpts from "The Horse: With a treatise of draugh and a copious index" by William Youatt
Published in 1831
"The Arabs have found out that which the English breeder should never forget, that the female is more concerned than the male in the excellence and value of produce; and the genealogies of their horses are always reckoned from the mothers."
"The Arabian horse would not be acknowledged by every judge to possess a perfect form; His head, however, is inimitable. The broadness and squareness of the forehead, the shortness and fineness o the muzzle, the prominence and brilliancy of the eye, the smallness of the ears, and the beautiful course of the veins, will always characterise the head of the Arabian Horse."
"The mare and her foal inhabit the same tent with the Bedouin and his children. The neck of the mare is often the pillow of the rider, and, more frequently, of the children, who are rolling about upon her and the foal: yet no accident ever occurs, and the animal acquires that friendship and love for man which occaisonal ill-treatment will not cause him for a moment to forget."
"When the Arab falls from his mare, and is unable to rise, she will immediately stand still, and neigh until assistance arrives. If he lies down to sleep, as fatigue sometimes compels him, in the midst of th desert, she stands watchful over him, and neighs and rouses him if either man or beast approaches."
"Man, however, is an inconsistent being. The Arab who thus lives with and loves his horses, regarding them as his most valuable treasure, sometimes treats them with a cruelty scarcely to be believed, and not at all to be justified. The severest treatment which the English racehorse endures is gentleness compared with the trial of the young Arabian. Probably the filly has never before been mounted; she is lead out; her owner springs on her back, and goads her over the sand and rocks of the desert at full speed for fifty or sixty miles without one moment's respite. She is then forced, steaming and panting, into water deep enough for her to swim. If, immediately after this, she will eat as if nothing occured, her character is established and she is acknowledged to be a genuine descendant of the Kochlani breed. "
"Our horses would fare badly on the scanty nourishment afforded the Arabian. The mare usually has but one or two meals in twenty-four hours. At night she recieves a little water; and with her scanty provender of five or six pounds of barley or beans, and sometimes a little straw, she lies down content, in the midst of her master's fmaily. She can, however, endure great fatibue; she will travel fifty miles without stopping; she has been pushed, on emergency, one hundred and twenty miles, and, occaisionally, neither she nor her rider has tasted food for three whole days."
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