Are equine tapeworms an emerging disease? A retrospective study

Abstract

Summary Surgical results have confirmed that 52% of horses in which the intestinal lumen was exposed had tapeworm infections. Of those infected, 63% were three years of age or younger. Similar results were seen in central Kentucky where 61% of the necropsied horses were infected. In our retrospective study covering over 23 years (1974–1997), 174 equids were necropsied in nine anthelmintic trials in which the compounds tested did not remove tapeworms. Of these, 79 animals were infected with Anoplocephala perfoliata and 12 additionally with A. magna. Over time, the percentage of A. perfoliata infections increased without respect to the animal's age. Infection with A. magna was inconsistent. There was an inverse relationship between percentage of infected animals and their age (65% of one to three years vs. 8% of 16≥years). The apparently optimum host for anthelmintic trials may be one to three years old as they show the highest rate of infection. The vast majority of fecal samples from infected animals were negative as prepared by standard centrifugal flotation techniques for sugar solution (Sp.G 1.20). The percentage of animals found with tapeworm eggs should be considered a minimum prevalence. The true infection rate should be considered to be much higher. In the UK, a serologic test using excretory/secretory antigen of A. perfoliata against anti-12/13 kDa IgG(T) from infected horses may be used for assessment of infection intensity, epidemiologic studies, and chemotherapeutic trials. As no drugs are labeled for treatment of equine tapeworms, various formulations of pyrantel or praziquantel are used against these parasites on an extra label basis.