Tapeworms: Can Cause Colic in Horses!

Mar 01, 2012
Disease tapeworms

Tapeworms are a member of a group of parasites called flatworms. Tapeworms are also referred to as cestodes. In the horse, tapeworms gather around the ileocecal valve in the cecum and attach to the mucosa with a scolex that has 4 suckers. They have no mouth parts or digestive tract, so they absorb nutrients through their cuticle. Equine Tapeworms are about 3 inches long by 1/2 inch wide.

Tapeworms: Anoplocephala magna and Anoplocephala perfoliata

  • Anoplocephala magna is the most common tapeworm in American horses and lives in the small intestine and rarely, the stomach and cecum.
  • Anoplocephala perfoliata lives in the caudal small intestine, cranial part of the cecum and occasionally the colon.

Life Cycle

  • Tapeworms survive via an indirect life cycle:
    • The Cysticercoid life stage lives within the intermediate host, the orbatid pasture mite, and takes 2 – 4 months to develop within the mite.
    • Horses ingest these mites in grass or feed.
    • Cysticercoid develops into adult tapeworm within small intestine or ileocecal junction within 6 – 10 weeks of ingestion of the orbatid pasture mite.

Signs of Infestation

  • Tapeworms tend to aggregate around ileocecal valves.
  • Can cause inflammation and ulceration of mucosa at site of attachment.
  • Mucosal ulcerations can develop secondary bacterial infections, may abscess or perforate bowel.
  • Heavy infections (> 300 worms) may cause blockage of the ileocecal junction inducing recurrent colic. If bowel perforation results, peritonitis and death occur.
  • Horses may be infested with tapeworms and show no clinical symptoms.
  • Clinical symptoms of tapeworm infection include depression, anorexia, diarrhea and colic.


  • 13% of horses infected with tapeworms may be passing eggs in their manure which means 87% do not have ova show up on fecal examination!
  • Tapeworm antibody blood testing is a more reliable way to diagnose tapeworm infection.
  • Antibody tests used to generate prevalence data for deworming product evaluations showed an overall infection rate of 54.2% of horses in the United States infected with tapeworms!


Treatment of choice is Praziquantel so using Ivermectin combined with Praziquantel (Zimectrin Gold or Equimax) or Moxidectin combined with Praziquentel (Quest Plus) are recommended at least once annually.


 Image curtesy of AP Pferdepraxis

Jessica Marsh

Written by Jessica Marsh, DVM