Targeted Deworming Advocated for Cushing's Horses

Horses with Cushing's disease (also called pituitary pars intermedia dysfunction, PPID) tend to have higher fecal egg counts (FECs) than healthy horses and might benefit from more aggressive parasite control measures, reported researchers from Oklahoma State University.

"While it has long been suggested that horses with PPID are more susceptible to internal parasites than healthy horses, until now, there was no published data to support this hypothesis," explained lead researcher Dianne McFarlane, DVM, PhD, Dipl. ACVIM, from the Department of Physiological Sciences at Oklahoma State's Center for Veterinary Health Sciences.

To determine whether FECs returned more quickly after deworming horses with PPID compared to healthy horses living in similar environments, McFarlane and colleagues dewormed 29 healthy horses and 13 horses with PPID with ivermectin. Small strongyle FECs were then calculated at two-week intervals.

"Horses with PPID had higher FECs than the healthy horses both before being dewormed and again at eight, 10, and 12 weeks after deworming," said McFarlane.

These results give credence to the widely-speculated theory that horses with PPID would benefit from custom-designed parasite control programs.

"While we found that horses with PPID were more likely to have high FECs, it was also true that some horses with PPID had low FECs, similar to that of healthy horses. Therefore, it is important to perform FECs in horses with PPID to establish their susceptibility to internal parasites. Then, with your veterinarian, an appropriate individualized strategic deworming program can be designed in light of the horse's risk and farm environment," advised McFarlane.

McFarlane's group at Oklahoma State University continues to study equine PPID and is working on understanding both the cause and the clinical consequence of this common disease of aged horses.

The study, "Fecal egg counts after anthelmintic administration to aged horses and horses with pituitary pars intermedia dysfunction," was published in the February 1, 2010, edition of the Journal of the Veterinary Medical Association. Co-authors were Hale, BS; Johnson, DVM, PhD; and, Maxwell, DVM, PhD, Dipl. ACVCP. The abstract is available online.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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