In this article, we pose questions about equine tapeworms to the world-renowned equine parasite expert Dr. Martin Nielsen. He is a DVM, PhD (parasitology), DVSc (doctor of veterinary science), DACVM (American specialist in parasitology), and DEVPC (European specialist in veterinary parasitology). He is the Schlaikjer Professor of Equine Infectious Disease at the University of Kentucky’s Gluck Equine Research Center.

Q. How can equine tapeworms negatively affect equine health?

The common equine tapeworm, Anoplocephala perfoliata, has been documented as a cause of colic related to conditions in the ileo-cecal region of the gastrointestinal tract. This is the junction between the small and the large intestine, where the tapeworms prefer to hang out. They attach to the intestinal walls just inside the cecum, and in case of larger burdens, they can be found in the ileum as well.

The ileum is a narrow-spaced section of the small intestine with a relatively rigid wall, which poses a risk of impaction (blockage) when worms reside there. Furthermore, to overcome the parasite blockage, the ileum attempts to pump them back to the cecum. This rigorous pumping can sometimes lead to intussusception. This is a condition where the intestine telescopes itself into an adjacent segment. The telescoped segment gets stuck, and surgery is required to correct the condition. 

Disease caused by tapeworms is still relatively rare. However, it is worth mentioning that it is more common than disease caused by small strongyle parasites. This places equine tapeworms as the number one parasitic pathogen among mature horses.

Q. We know many equine internal parasites are becoming or have become resistant to available anthelmintics. Is the same true for tapeworms?

Yes. Unfortunately, we have been documenting complete treatment failure of both currently available anthelmintics for tapeworms—praziquantel and pyrantel pamoate. This appears to be widely common in some areas.

We are concerned that this could be another worldwide phenomenon. This is particularly concerning because we don’t have any alternatives to these two anthelmintics for tapeworm control.

Q. What can horse owners do to control tapeworms with anthelmintics and management?

The number one thing to do is to talk to their veterinarians about checking the treatment effectiveness. Is praziquantel working? And what about pyrantel? 

Consider the environment. We know that tapeworm transmission requires access to green pastures. Therefore, horses living in arid parts of the world may not be heavily exposed to infection.

There is very little evidence documenting the effects of pasture management on tapeworm control, but maintaining good, healthy pastures and avoiding overstocking are elements of good husbandry. That should decrease the infection pressure. 

Q. Anything else you would like to mention?

It is important to mention that opposed to the nematode parasites (such as ascarids and strongyles), we don’t observe any apparent host immunity to tapeworm infection. A senior horse is just as likely to harbor tapeworms as a yearling.

The deciding factor appears to be time on pasture. The more time a horse spends on pasture, the higher the risk. So, this may put retired horses at a higher risk than performance horses that spend more time in stalls and on dirt paddocks.

Further Reading

  • Kimberly S. Brown
    Kimberly S. Brown is an award-winning writer and publisher. She is the Editorial Director for My Senior Horse. Brown spent 10 years at Equine Network, parent company of My Senior Horse. Prior to that she worked for three years in equine nutrition after she retired from nearly 30 years working at The Blood-Horse. Brown spent the last 15 years of her time at that organization creating and developing The Horse and TheHorse.com.
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