The relationship between internal equine parasites and the risk of colic has been widely known in the cases of several types of worms that infect horses.  In recent years, there have been significant advancements in the understanding of equine tapeworms, the damage they inflict, and their role in equine colic.1  Equine colic is the single most important noninfectious cause of mortality in horses, and parasitism is one of many factors which can lead to colic. Fortunately, this is one of the easiest factors to control through knowledge of a parasite’s life cycle and strategic use of dewormers that can help to control infection.  

The equine tapeworm (Anoplocephala perfoliata) is ubiquitous in most places where horses have pasture access. However, their presence largely depends upon favorable climatic conditions for the orbibatid mite, which is the tapeworm’s intermediate host. In dry and arid states in the US southwest (for example), horses are rarely exposed to tapeworms. 

The overwhelming majority of horses harboring tapeworms tolerate them without any signs of discomfort or development of colic. It is not entirely known why tapeworm-related disease occurs in some horses and not others, but there are several possible reasons. In some cases, a proliferation of the worms may occur (high infection pressure), which could be driven by climatic conditions or overstocked paddocks and pastures. In other cases, a horse with a suppressed immune system may be more susceptible to a heavy tapeworm infection.

Tapeworm Infection in Equines

A. perfoliata live at the junction between the ilieum and the cecum, where the small intestine connects to the large intestine.2 The worms attach to the intestinal wall just inside the cecum. Thus, the resulting colic is related to the ileocecal region. In very rare cases, the intestinal tract can twist and rupture.1 

Tapeworms infect horses of all ages, and horses do not appear to establish immunity to them.2 Clinicians have observed that weanlings and yearlings experiencing their first tapeworm infection may be particularly at risk for developing ileocecal colic. Thus, many owners and managers begin tapeworm treatment right around or shortly after foals are weaned.

Research has shown that fecal egg counts generated with the McMaster technique do not reliably detect tapeworms, and often miss more than 90% of infected horses.1 Fortunately, other methods can detect at least 90% of horses with worm burdens of as little as 20 worms. Veterinarians can also detect antibodies against A. perfoliata in serum or saliva. The presence of tapeworm antibodies means that a horse is either currently infected or has recently been exposed to A. perfoliata in its environment. 

Where to buy Praziquantel

Praziquantel is available in the U.S. through pharmaceutical manufacturers and through veterinary custom compounding companies. 

Praziquantel carries several potential drug interactions. Please consult your veterinarian prior to beginning any treatment regimen.

FOR RX ONLY: A valid prescription from a licensed veterinarian is required for dispensing this medication.

1aaep.org.

2Merck Veterinary Manual.