Research News: 07/06

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Targeting Small Strongyle Larvae

A study performed at Justus Leibig University in Germany, published in Veterinary Pathology, looked at the response to larvicidal deworming with either Quest (moxidectin) or five days of double dose Panacur (fenbendazole) in ponies heavily parasitized with small strongyle larvae.

Reduction in the number of parasites in the bowel wall began four to six days after starting the fenbendazole and six to 14 days after starting moxidectin. Both were effective in significantly reducing the number of parasites, but the fenbendazole treated ponies developed an inflammatory response around the dead larvae that in some cases was severe enough to cause ulceration of the bowel lining at the 14-day mark (14 days after starting treatment, 9 days after ending treatment). They did not mention any symptoms associated with the damaged gut wall, but that’s certainly a possibility.

The greater inflammatory response and gut damage following fenbendazole treatment has to be weighed against the much higher incidence of reported suspected adverse events following moxidectin (FDA adverse drug event reporting). Moxidectin dosing should always be based on an accurate body weight and some veterinarians feels animals with little body fat are at higher risk of side effects. If you use fenbendazole, pretreatment with ivermectin will kill the late L4 stage larvae that started the inflammatory reaction in this study. When deworming a heavily parasitized horse, involve your veterinarian.

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Prepurchase X-Rays

A study performed at the University of California, Davis, examined both front legs of the cadavers of 328 racing Thoroughbreds and found sesamoid bone fractures in a whopping 41.5% of those legs. Evidence of sesamoiditis, including bone proliferation as osteophytes and enlarged vascular channels, were found in 81% and 99% of the legs, respectively. As an interesting observation, horses that didn’t have evidence of sesamoiditis were two to five times more likely to have fractures. In any event, a high percentage of these horses have problems in their fetlock joints that could have a negative impact on their soundness. If considering buying a ex-racehorse, it would be wise to include radiographs of the fetlocks in your prepurchase exam.

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New Technique For Fusing Hocks

”Bone spavin” is a degenerative arthritis in the hock joints. It’s common in all disciplines, especially with horses that work heavily off their hind ends, such as working Western horses, dressage horses and horses that jump.

The condition slowly erodes away the cartilage between the small hock bones in this complicated joint, and results in the development of painful bone spurs along the edges of the joint. These spurs form as an effort by the horse’s body to bridge the bones with solid bone, a process called ”fusion,” so that there is no more movement and irritation. When fusion occurs in the lower joint of the hock, it has no significant effect on movement but does eliminate the pain.

Veterinarians have tried many things over the years in attempts to hurry along this fusion process, which can take years and in some cases never does completely occur on its own. Various surgical techniques and injections have been tried, with limited success and often considerable discomfort to the horse. An article in the American Journal of Veterinary Research is offering some hope.

Researchers in Canada at the University of Saskatchewan studied the effects of injections of either 70% or 95% ethyl alcohol (140 proof or ”grain”) into the joints of horses with hock arthritis. 50% of the treated joints were fused 4 months after treatment, most in the 70% group, and 15 out of 16 injected joints were completely fused at the 12 month mark. An added plus was that the ethyl alcohol treatment caused no pain. Further studies on larger numbers of horses are needed, but these preliminary results are promising.