Ruthless Parasites: Tapeworms and Bloodworms in Horses

Worming Is Essential To Keep Your Horse Healthy

In the old days it was necessary to deworm your horses via a tube passed from through the nasal tract into the intestines. Fortunately, since the advent of easily swallowed oral pastes, this ordeal is a relic of the past. Even the dewormers that came on the market promised a victory in the war on parasites.

Yet while most parasites can thus be controlled, two in particular require greater care: the strongyles, a.k.a. bloodworms who have been blamed for winter cyanthostomiasis and the tapeworms that have been held responsible for some types of colic. Thus far, there are more than 40 known species of bloodworms, of which about 10 to 15 are found within horses.

Because of their noted ability to attain immunity to some of the dewormers now used, their parasitic activity occurs even in winter, which makes them a bit easier to diagnose. While any horse may be affected, it is the young horse that is most often affected. You may see weight loss, swollen bellies, bouts of diarrhea, and also colic. While in the past if was thought that only horses who were not on a regular deworming schedule would be affected, it has since been found that symptoms of infection may occur even after rigorous deworming protocols have been observed.

The causes for such a winter infection have not been completely nailed down, but theories abound. One theory holds that if a severe winter follows on the heels of an unseasonably warm fall, the odds are good that the development of cysts within the horse’s intestinal wall may be arrested. As the larvae may develop the cysts within the horse when the fall is wet and warm, it is not surprising that the number of parasites suddenly spikes, and the signs of infestations are the result.

Research has shown that exposure to shed larvae in the southern portions of the United States may occur during a mild winter while in the northern areas it is the spring and fall that bring the dangers of infection. Some veterinarians believe that the susceptibility of horses for the parasitic infection rises also because seasonally schedule dewormers will have killed off the other lifecycle stages of the bloodworm, thus signalling the left over cystic worms to emerge.


After all, the cysts prevent this particular stage from being affected by any dewormer. To this end, it is now recommended that in addition to the regularly scheduled dewormer, a larva killing treatment also needs to be administered to your horse. Protection against the larvae is achieved by giving the chemical to your horse daily over the span of a week, or as often as recommended by your veterinarian. In addition to this regimen, you should also avoid spreading manure over the pasture.

Since the larvae are highly susceptible to damage brought on by heat and dryness, be sure to capitalize on the heat of the summer and break up any manure. During the other times, you may just need to go ahead and pick it up to avoid your horses being exposed to the larvae. While bloodworms can wreak havoc with your horse, tapeworms are not a laughing matter either.

Once they were not considered to be much of a problem, but considering that they are associated with colic and severe inflammation and swelling, they are now actively targeted during dewormings. It is interesting to note that tapeworms will most likely enter your horse while it ingests vegetation that contains mites which in turn have ingested the parasitic eggs. Generally speaking, horses living in areas that contain swamps are more commonly found to be affected with tapeworms.

Fortunately, there is a drug available to successfully free a horse from this parasite, and a regular dose should do the trick. Yet since there is a 30 percent change of there being remainders, it is best to double the dose once or twice per year. Obviously, you will want to discuss this with your veterinarian before proceeding.

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