Researchers Complete 40-Year Parasite Study

Researchers at the University of Kentucky's Gluck Equine Research Center recently completed a 40-year investigation of drug-resistant small strongyles in horses. E.T. "Gene" Lyons, PhD, a researcher at Gluck, said the study offered information that could help horse owners and clinicians better understand parasitism in horses. The study was published in the July issue of Parasitology Research.

Lyons said, "The information from this study is unique because of accurate records kept over an almost 40-year period on antiparasitic compounds used and frequency of usage. The purpose of the data was mainly to provide (quantification of) the prevalence of internal parasites in horses of known age in a closed herd, without antiparasitic usage for many years."

The study included 14 horses ranging from 239 days old to 23 years old housed on two separate lots. Lyons said it had been 26 years since the horses in one lot had been given any type of dewormer and nine years since the other lot's horses had received anthelmintic treatment.

He said the study provided many unique pieces of information such as:

  1. Bots (Gasterophilus intestinalis) were found attached to an unusual part of the stomach (i.e. the glandular part, not the usual esophageal part). While bots rarely perforate the stomach wall--theoretically they could more easily do so when attached to the thinner-walled glandular portion of the stomach.
  2. Large strongyles (Strongylus vulgaris and S. edentatus) were found in the large intestine and S. vulgaris were found migrating in the cranial mesenteric arteries even in horses older than 20 years old. This verified previous findings that older horses are not completely immune to these parasites. 
  3. Tapeworms (Anoplocephala perfoliata) were found in all ages of horses.
  4. Adult pinworms (Oxyuris equi) were found in the oldest horses (21 and 23 years of age) ever recorded in Kentucky.

Lyons said, "Like most research, it is not 'earth-shattering,' but each small aspect may contribute to the larger picture of parasitism in horses."

About the Author

Chad Mendell

Chad Mendell is the former Managing Editor for .

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