Equine Tapeworms: A New Old Threat?
R. Paul Schwab, D.V.M.
Kulshan Veterinary Hospital
As probably many of you have noticed, there has been a sudden surge of products available to treat tapeworms in horses. Tapeworms, although frequently diagnosed in small animals, have been somewhat of a mystery in horses. We have known for years that horses do get tapeworms, and that they are responsible for some colics, but until recently veterinarians have had neither good diagnostic procedures for finding them or good products for treating them. This has changed lately with the advent of new testing methods that look for antibodies in the blood stream against tapeworms. Dr. Craig Reinemeyer, looking at banked serum samples from old Coggins tests, found the prevalence of horses exposed to tapeworms to be from 12 to 95%. The prevalence in WA was found to be about 33%, possibly higher in the wetter west side. The national average is about 54%.
The adult tapeworms live in the horse’s digestive tract, almost exclusively on or near the ileo-cecal junction. This is where the small intestine empties into the cecum, which is a part of the large colon. Segments of the tapeworm are intermittently shed into the fecal material where they release eggs as they are broken down. This is why we don’t see tapeworm segments like we do in dogs and cats. The Orbatid mite, a very common mite in the soil and grass eats the eggs from the manure piles. These mites harbor the eggs until they are eaten by the horse off the ground or in the hay or bedding. The larva attach in the horses cecum where they grow to adults and start the cycle over again.
Since the tapeworms live almost exclusively in one location in the horse’s intestine, they can create quite a lot of inflammation and irritation to the gut lining. Studies have reported that 22% of spasmodic colics and 81% of ileocecal impactions are associated with tapeworm infestation.
So how do you know if your horse has tapeworms? Well that’s the hard part. Fecal floatation is the technique we use to look for most parasites. We put some manure in a sugar solution then spin it down in a centrifuge then let it sit for a while. The parasite eggs then float to the top. This method is only about six percent effective in locating equine tapeworms. They must have very large numbers in order to find the eggs. There is the blood test that was used by Dr. Reinemeyer to determine the prevalence of tapeworm exposure in horses, but it is not widely available for commercial use. We may diagnose tapeworms on certain horses based on specific types of colic like the ones mentioned above.
What we can do now is treat and control tapeworm infestations. There are three products available for removing tapeworms: Equimax, Zimectrin Gold, and Quest Plus. All three products combine an Avermectin dewormer with Praziquantel. These combinations are very broad spectrum, killing not only tapeworms and most other worms, but also bots and lice. Most literature shows that tapeworms may have higher numbers in the late summer and fall, making late fall/early winter an excellent time to use these combination dewormers. You’ll also be taking care of the bots at a good time. For those of you on the Strongid C daily dewormer, it is recommended to use an avermectin dewormer twice a year. We would recommend using one of the avermectin/praziquantel combination dewormers in the fall unless your veterinarian recommends otherwise. Also, Strongid C may have some small activity against tapeworms.
These deworming strategies are only general guidelines. For a more complete deworming program, talk to your veterinarian regarding your specific situation.
