Controlling parasites in horses is a gross but fascinating part of providing veterinary care. This spring we will take a little time to explore a few of the different parasites affecting horses and how we recommend treating your horse for them and managing your property to help reduce them. Parasites naturally involve talking a lot about poop :) But all veterinarians love talking about your horse's poop so enjoy!
Tapeworms are one of the most recognized parasites in popular culture and they can infect most species. The tape worm most commonly found in horses is Anoplocephala perfoliata. This parasite infects horses through an intermediate host, the orbatid mite. The mites live on grass pastures where they are infected with the parasite which then passes on to horses when they graze. The moister a pasture environment is, the higher the number of orbatid mites are present and the more likely a horse is to be infected. The south east is an area of high prevalence for this parasite and it is important to protect horses appropriately!
What are the signs of tape worm infection?
Most tape worms don’t cause any noticeable harm to horses unless they are present in large numbers or in foals. The parasites cause little sores in the intestine where they attach to the wall and if in large numbers may pre-dispose a horse to an ileocecal (small intestinal) impaction. We do not generally assume a thin horse has a tapeworm because so many things contribute to weight loss in horses. However, it can definitely contribute to an animal’s inability to gain weight or have a healthy hair coat in the face of good management, nutrition and care.
How do you know if your horse is infected?
It is very hard to diagnose tapeworms using the traditional method of fecal egg counting. While we recommend this test as an excellent way to diagnose other parasite infections such as round worms or strongyles, often tapeworms are not shedding eggs at the time the test is performed and they cannot be detected in the feces. Also tapeworms tend to release all their eggs at once in a packet called a proglottid. Therefore the number of eggs found does not always correspond to the number of worms or severity of infestation. One way to determine if your horse is harboring a tapeworm is to treat him and collect his feces 24 hours later and perform a fecal egg count, if eggs are present he likely was infected!
How do you protect your horse from tapeworms?
Since tapeworms are very common in a horse’s grazing environment it is safe to assume that most horses are exposed and likely infected at some point in their life. Because of this we recommend all horses be treated for tapeworm infection at least once a year. In order to make your pasture safer and reduce the number of tapeworms that will infect it the next year it is best to treat your horse for tape worms in the late fall or winter when it has become cold and transmission of the parasite ends for the season. Praziquantel and a doubled dose of pyrantel pamoate (Strongid) are the only drugs available to treat tapeworms in horses. Praziquantel is often packaged with ivermectin or moxidectin in products such as Equimax, Zimectrin Gold, and Quest Plus. At Covered Bridge Equine we generally recommend deworming with one of these drugs in December-February as part of your complete parasite control program.
Sources:
AAEP Parasite Control Guidelines. Developed by the AAEP Parasite Control Subcommittee of the AAEP Infectious Disease Committee.
Figure 1 -
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4031382/ Tomczuk, K., Kostro, K., Szczepaniak, K. O., Grzybek, M., Studzińska, M., Demkowska-Kutrzepa, M., & Roczeń-Karczmarz, M. (2014). Comparison of the sensitivity of coprological methods in detecting Anoplocephala perfoliata invasions. Parasitology Research, 113(6), 2401–2406. http://doi.org/10.1007/s00436-014-3919-4