Mites in Drafts: Simultaneous Treatment Not Effective

Luxurious, flowing feathers are a hallmark of many draft breeds. Without proper care, however, the thick lower-leg hair can become a virtual incubator for external parasites, setting the stage for skin conditions that are difficult to treat.

One common mite that triggers pastern dermatitis in horses is Chorioptes bovis. If severe enough, pastern dermatitis can progress to chronic edema of the distal limbs, formation of thick skin folds with wartlike lesions, and lameness.

Researchers at the University of Berne, Switzerland, studied the efficacy of oral moxidectin in controlling C. bovis infestation in a double-blind, placebo-controlled study using 19 heavily feathered horses. Moxidectin was given twice in a three-week interval in combination with a bactericide and insecticide bath.

Follow-up examinations over a 180-day period revealed significantly more skin crusting in the placebo group than in the treatment group. Despite this, no other differences in clinical signs or the numbers of mites detected were found between the two groups.

Moxidectin in combination with environmental insecticide treatment proved ineffective in the treatment of C. bovis in feathered horses.

The full article, titled “Combined moxidectin and environmental therapy do not eliminate Chorioptes bovis infestation in heavily feathered horses,” was published in the July 2010 issue of Veterinary Dermatology.