Basic Strongyles Facts for Horse Owners

Internal parasites like strongyles are among the most harmful to horses. If left untreated, these organisms can lead to serious organ damage and can pave the way to serious health complications. The best first step for every horse owner is to keep informed. Find out more about these parasites so you’ll know what to do when they strike.

Large Strongyles

There are three species of this large version of the parasite, Strongylus equinus, Strongylus vulgaris and Strongylus endentatus. Of these three, S. vulgaris is the most deadly. Once inside, this parasite enters intestinal walls and the arteries that transport blood to the intestines and neighboring organs. The parasite will cause blood clots or embolisms, thereby disrupting efficient blood supply. After a few months, the larvae migrate further into the large intestine and become adult worms. Aside from laying eggs, these worms also begin sucking blood which may lead to anemia.

The other two species of strongyles may be less damaging but they can be lethal too. The larvae of these species tend to migrate to the liver where they can cause damage. Like S. vulgaris the two other species return to the large intestine where they become adults and lay eggs.

Small Strongyles

The small versions of these parasites differ from the large ones in that they do not move beyond the intestinal walls. They will instead migrate to the walls where they encyst themselves. They may stay in this state for as long as three years. Once they are rooted in the intestinal walls, they can cause anemia, nutrient deficiency, bleeding and colic. Larvae that emerge from the walls may also cause diarrhea and inflammation.

How Horses are Infected

Both large and small strongyles share a similar life cycle. Eggs that are laid by adults accompany fecal matter as they exit the horse’s system. Once the eggs are out, they may hatch under good weather conditions. The larvae then undergo three molting stages, the last one being their infectious state. Although they can stay in a molted state for about ninety days, they must be ingested by a host to enable efficient infection.

Obviously, horses are typically infected when they eat grass that carries strongyles. The parasites in grass can be very hardy. They can remain buried in soil to protect themselves from unfavorable weather conditions and then climb up the blades of grass where they are in a position to infect a foraging horse.

Prevention and Treatment

Horse owners may attempt to prevent strongyles infections by ensuring clean stables and foraging grounds. Even the cleanest surroundings however, do not always ensure 100% protection against infections. The best preventive measure and treatment solution for strongyles is regular deworming. In other words, you should have a schedule for horse deworming even if you are not sure that your horse is infected. This is especially since it may take some time for the parasites to be detected in fecal matter. Without a regular deworming schedule, strongyles may progress to severe stages at which point deworming will be ineffective.