Fall and winter are seasons often associated with equine colic. When faced with a case of impaction colic, the first thing that may come to mind is dehydration, perhaps because a horse didn’t drink enough or didn’t have access to ice-free water. But, it is possible that an impaction might instead be due to tapeworms. Recently in Kentucky there have been more than the usual cases of ileocecal intussuseptions presented for surgery (according to a report from Hagyard Equine Medical Institute). At surgery, the inciting cause was found to be an infestation of tapeworms, in particular Anoplocephala perfoliata.
The unseasonably warm winter temperatures this year have precluded the necessary freeze to kill the oribatid mites that serve as an intermediate host in the tapeworm life cycle. It is relevant to advise horse owners about the importance of implementing praziquantel into their deworming schedules, once or twice a year. This is particularly applicable to horses grazing on pasture where they are at greatest risk of exposure to oribatid mites that may contain tapeworm eggs. In areas of the country where freezing temperatures are not prevalent during the year, twice a year administration may be the best strategy. In more wintry climates with freezing temperatures, once a year deworming with praziquantel may be all that is necessary. Praziquantel is reported to exert a 95% kill rate on Anoplocephala perfoliata.
Clinical signs of tapeworm infestation vary depending on the numbers of tapeworms attached to the ileocecal junction. Their damage to the cecal mucosa can interfere with bowel motility, leading to impaction or intussuseption. Because of motility disturbances, even a light infestation may cause spasmodic or gas colic, with 22% of these types of colic attributable to tapeworms. Heavier infestations may cause the ileum to telescope into the cecum, resulting in vascular compromise, necrosis, and potential bowel rupture; these conditions are accompanied by intense colic pain.
Incidence of tapeworm infestation in horses varies depending on geographical location, ranging from 17% in the Pacific Coast regions to 95% in the Midwest. While many horse owners have stepped up to implement praziquantel into their deworming schedules to address tapeworms, not everyone is aware of the inherent danger of this parasite. Informing clients about parasite control strategies specific to your geographic locale is an excellent topic for optimizing client communications and client use of veterinary services.