Typically combined with ivermectin in a blended dewormer, praziquantel is generally considered a safe and effective means of treating tapeworms in horses. While they haven't been on the radar long in terms of parasites to be concerned about, tapeworms can actually cause severe intestinal and colic issues, and the tapeworm host is a mite commonly found in enormous quantities on the healthiest of pastures.

 

Tapeworms are a type of parasitic flatworms in the Cestoda class; they attach to a horse's intestinal lining via hooks or suckers on the head. As flatworms, they don't possess a body cavity, or some specialized organs like respiratory or circulatory systems; instead, oxygen and nutrients pass through their flattened body structures.

Of the three types of tapeworms found in horses, Anoplocephala perfoliata (A. perfoliata) is the most common, followed by A. magna; while possible, Paranoplocephala mamillana is rarely found. You can read more about tapeworms in our February 2010 Worm of the Month article found in our Archive.

Tapeworms find their way into the horse via the plentiful oribatid mite, tiny organic-matter-eaters that are essential in healthy pastures and forests; they consume tapeworm eggs while eating and 'recycling' organic materials. Horses can pick up the infective mites, which are only about a millimeter long, in grass, hay, or even bedding, ingesting the mites with tapeworms inside them. The tapeworms then mature inside the horse within six to ten weeks. For a detailed description of the tapeworm, the oribatid mite, and how to interrupt the tapeworm lifecycle, we recommend the '˜Tapeworms Uncovered™' article available as a free PDF download from TheHorse.com.

   

Tapeworm infestations are now thought to be fairly common, but they've been historically difficult to prove because tapeworms rarely show up in identifiable form in manure or during fecal exams; this is different than with dogs and cats, where tapeworm segments can easily be seen in feces. Many adult horses will show tapeworm antibodies when blood-tested, however this doesn't necessarily indicate current problems. Post-mortem research has shown that tapeworm infestation can be as high as 60%, but who wants to cut open their horse to find out if he has tapeworms?

 

With the difficulty in identifying tapeworm infestations in live horses, many now feel that an annual dose of praziquantel, combined with ivermectin or moxidectin, can be a sound prophylactic measure in keeping horses healthy. Once praziquantel became available off-patent, several companies combined it with either moxidectin or ivermectin, under brand names such as Equimax, Zimectrin Gold, and Quest Plus; this allowed low-cost treatment for tapeworms alongside deworming for strongyles and roundworms.

 

While praziquantel is generally considered safe, newly dewormed horses should be watched for the first day for signs of adverse reactions, or for signs of colic that can result if the tapeworm infestation is severe and the dead parasites clog the horse's intestines on the way out.

 

As for the health problems tapeworms can cause, they can include both spasmodic and ileal impaction colics; inflammation of the gut from the tapeworm attachment points; thickening of the intestinal wall resulting in slowed or blocked movement of food through the digestive tract; ruptures of the small intestine; and Ileocecal intussusception, a condition where the intestine doubles back on itself. Many of these conditions can only be corrected through risky surgery, so when it comes to tapeworms, prevention through praziquantel can be the best course of action.

 
If you want to read up on specific parasites or dewormers we've covered, check our Archive for past Worm of the Month articles.

If we can be of help, please email us at hlab@horsemenslab.com or call us at 800-544-0599.