Tapeworms? Storm in a Teacup or Major Concern
24 March 2011
Tapeworms are so called because of their appearance. They are generally broad and flattened and contain segments. These segments are in effect egg packets and are shed from the end of the worm one-by-one, so that the stool is infested and in turn, the pasture becomes infested, allowing the continuation of the species. There are a number of species of Tapeworm that affect the horse. The most commonly observed species in horses in Ireland and the UK is known as Anoplocephala perfoliata.
Image of a typical tapeworm. Note the rounded head (top right had corner) and the flattened segmented appearance of the posterior end (bottom left hand corner)
Life Cycle of the tapeworm:
The life cycle of the tapeworm hinges on tiny mites. These mites present a perfect growing site for the immature tapeworms (cysticercoids). The cysticercoids emerge from the horses stool, infest these mites and wait on the pasture until consumed by a horse. When the mite containing the infective cysticercoids, is digested, the tapeworm larva is released inside the horse. The tapeworm uses its hook- like teeth to latch onto the intestinal lining of the large intestine. There the larva grows into the fully grown, segmented, tapeworm. Each segment of the worm contains eggs which the tapeworm releases into the digestive tract of the horse. The segment coating is dissolved and the eggs are released into the stool where they're eaten by the mites. Eggs must develop in the mite for a few months to reach the cysticercoid stage and become infective. These mites live in the grass and are eaten by grazing horses, starting the cycle over again. The life cycle therefore, usually takes a number of months to complete itself. This fact alone, makes tapeworm relatively easy to control, as it may take a considerable amount of time for very heavy worm burdens to accumulate.
Diagnosis is by demonstration of the characteristic eggs within the stool. However, as the shedding of egg sacs is not continuous, more than one faecal egg count may be required to get a definite diagnosis. There is also a blood test for detecting tapeworm in horses that detects tapeworm antibodies. However, although this blood test will tell whether or not the horse has tapeworms, it merely gives a broad indication of the levels of tapeworm present and not specific numbers.
In light infestations, no signs of disease are present. However, in heavy infections, loss of weight and intestinal disturbances such as colic and peritionitis may be seen. In stables where these tapeworms are prevalent, infections can be prevented by pyrantel embonate (the active agent within Embotape). These preparations require the administration of a double dose for most effective treatment of tapeworm infestation.
Treating horses with pyrantel embonate immediately before turn out and at the end of the grazing season is likely to be most beneficial and can be easily applied into individual horse worming strategies or applied to all horses on a given property. For more information on Embotape or any of the Bimeda horse products, contact your local agent or veterinary surgeon.