Detecting Tapeworms, Reducing Resistance through 'Diagnostic Deworming'

Diagnostic deworming of horses with anti-tapeworm drugs could play an important role in reducing resistance to antiparasitic drugs, report veterinarians from Japan and North America.

Tapeworm infections are an important issue in equine health. Infections are difficult to detect because the available tests are unable to reliably detect or quantify parasite burdens.

"While infections are often subclinical, some evidence exists that tapeworms can concentrate at the ileocecal junction and contribute to volvulus (twisting) or rupture of the cecum," explained Hajime Nagahata, DVM, PhD, from the school of veterinary medicine at Rakuno Gakeun University. "Knowing the tapeworm status of horses is important."

Prior research revealed that large numbers of tapeworm eggs were identified in fecal samples obtained from horses after deworming with pyrantel pamoate; therefore, Nagahata and colleagues treated 12 Thoroughbreds (seven mares and five foals) with bithionol (5-10 mg/kg), an anti-tapeworm drug available in Japan, and collected feces on days 0, 1, and 10 of the study.

"Fecal tapeworm eggs were increased in all 12 of the treated horses, including three horses that were negative for tapeworm eggs prior to bithionol administration," relayed Nagahata. "The optimum time for detecting eggs to tapeworms was one day post-treatment."

The study authors recommend that this diagnostic deworming technique should be applied to a fraction of every herd, and, in the face of high infection rates, the entire herd should be dewormed.

According to Andrew Peregrine, BVMS, PhD, DVM (Hons) Glasgow, Dipl. EVPC, MRCVS, from the Department of Pathobiology at the Ontario Veterinary College in Canada, "Since we are trying to reduce the amount of dewormers given to horses to decrease the rate of selection for anthelmintic resistance, testing a cohort of horses (approximately 10 per herd) after worming with pyrantel pamoate, for example, does make sense. I haven't heard of anyone doing this yet, but would not be surprised if I soon do."

The study, "Evaluation of marked rise in fecal egg output after bithionol administration to horses and its application as a diagnostic marker for equine Anoplocephala perfoliata infection," was published in the May 2009 edition of the Journal of Veterinary Medical Science.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.

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