UK Researchers Awarded Grant to Study an Avermectin Dewormer

A team of researchers at the University of Kentucky (UK) Department of Veterinary Science received a $19,285 Koller Fund grant to study the pharmacokinetics (study of a substance administered externally) of moxidectin, a type of avermectin dewormer. Moxidectin is used to treat and prevent external and internal parasites in the horse and other species.

Cindy Gaskill, DVM, PhD, clinical veterinary toxicologist at the UK Veterinary Diagnostic Laboratory (UKVDL); Martin Nielsen, DVM, PhD, EVPC, assistant professor at the UK Gluck Equine Research Center; and Lori Smith, PhD, senior chemist, toxicology, at the UKVDL are the investigators of the grant.

Macrocyclic lactone (ML) anthelmintic intoxication can occur in horses from overdoses, from interactions with other drugs or plant compounds, or from inappropriate dosing of very young or old animals. Signs of ML intoxication occur due to excessive accumulation of the drugs in the brain. Confirming ML poisoning as a cause of death can be difficult, especially if the owner provides no history of known exposure. The best post-mortem confirmatory test is by measuring drug concentrations in the brain tissue.

The UKVDL has recently received a number of horses for post-mortem evaluation with histories of neurologic abnormalities and suspected exposure to the ML anthelmintic moxidectin at unknown doses. Several of the horses came from Central Kentucky farms.

As stated in the grant proposal, “Results of this study will help confirm or reject a diagnosis of moxidectin intoxication in these horses.”

The grant will further help the researchers determine expected brain concentrations of moxidectin post-therapeutic dosing in horses and develop a quantitative HPLC (high performance liquid chromatography) method for macrocyclic lactone anthelmintic (e.g., moxidectin, ivermectin) analyses in equine brain tissue.

Jenny Evans, MFA, is the marketing and promotion specialist senior at the University of Kentucky Gluck Equine Research Center.

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