Trichostrongylus spp in Horses

Trichostrongylus spp in Horses - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost
Trichostrongylus spp in Horses - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost

What is Trichostrongylus spp?

Trichostrongylus spp in horses is a small stomach parasite, or worm, known as a hairworm. This worm also affects ruminants, such as cattle. Typically, if a horse shares a pasture with cattle, they are more susceptible to infestation from this worm. Belonging to the family known as Strongylidae, they are also referred to as roundworms. There are approximately thirty species of this parasite around the world and some species can actually infect humans. This happens more so in Asia and Africa where there are rural areas with poor sanitary conditions. The actual species of Trichostrongylus spp that affects horses is known as Trichostrongylus axei.

The adult Trichostrongylus axei are very thin and can grow to 8mm in length. In terms of the life cycle of this parasite, infestation in horses has not been thoroughly studied. Researchers do know that these parasites enter the mucosa in the form of larvae. Once the larvae penetrate the mucosa, lesions begin to be evident. The lesions that occur are commonly found in the glandular area of the stomach, and can be very small or large, depending on the infestation. The lesions are typically covered with mucus and are quite congested.

Trichostrongylus spp in horses is a parasite worm that penetrates the horse’s mucosa. This parasite causes gastric distress and is commonly found in horses that share pasture with cattle and other ruminants.

Symptoms of Trichostrongylus spp in Horses

If your horse has been infected with Trichostrongylus spp, he will exhibit the following symptoms. If you notice any of these symptoms, contact your veterinarian. Symptoms may include:

  • Weight loss
  • Lesions
  • Ulcerations
  • Diarrhea
  • Constipation
  • Weakness
  • Lethargy


There are several types of animals that Trichostrongylus spp can affect. Horses that tend to graze in the same pastures or farms of susceptible animals have a higher risk of becoming infected. These ruminants and other animals are affected worldwide, and include:

  • Pigs
  • Goats
  • Cattle
  • Sheep
  • Poultry
  • Deer
  • Antelope
  • Camels
  • Monkeys
  • Wild boars
  • Zebras


Causes of Trichostrongylus spp in Horses

Causes of infestation and potential sickness from the parasite are definitive in cattle and ruminants, as much research has been conducted on the worm within these animals. Causes of infestation and illness in horses may include:

  • Horses sharing pasture with cattle or ruminants
  • Trichostrongylus spp impacting the lining and wall of the small intestine
  • Contaminated soil ingestion
  • Larvae penetrating the mucosa of the horse
  • Larvae grow to adult worms within the horse’s stomach


Diagnosis of Trichostrongylus spp in Horses

If your horse is exhibiting any of the above symptoms, make an appointment with your veterinarian. Your medical professional will want to know more information about your horse’s health history, his grazing lifestyle, the cleanliness of the pasture, if he grazes with cattle, and if he is having any other symptoms. He may also ask when the symptoms began and the severity of the symptoms. 

Your veterinarian may do blood testing and any other laboratory tests to rule out any other conditions. Although challenging to make a definitive diagnosis by looking at the feces, your veterinarian may perform a fecal examination. The eggs are very similar to the eggs of strongyle. Your veterinarian may be able to identify any worms within horse’s feces.



Treatment of Trichostrongylus spp in Horses

If your horse has been subjected to infestation of the hairworm, your veterinarian will provide a few treatment options to help him overcome the parasite and any sickness that has ensued. Treatment methods may be comprised of:

Anti-Parasitic Medications

Anti-parasitic medications are used to treat the Strongyloides. Your veterinarian may prescribe them for your horse; he may prescribe Ivermectin or a type of benzimidazoles recommended by him to kill the parasites within your horse. Other anthelmintics may be prescribed depending on your horse’s condition and the severity of the infestation. 

Clean Pasture

In addition to treatment with anti-parasitic medications, horses, namely brood mares, need to be moved to pastures that are clean while avoiding overcrowded areas. The foals are very susceptible to this parasite as well. Feces need to also be removed, and this can be managed by plowing on a regular basis to keep the ground from becoming too dense. In order to continue treating this parasitic infestation, a system of grazing management should be in place.


You will need to continue to monitor your horse’s stools to be sure his system is clear. This should be done on a regular basis.



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Recovery of Trichostrongylus spp in Horses

With proper treatment, your horse can recover from infection and be clear of parasites; however, it is important to maintain proper measures to prevent any reinfestation.  Cleanliness is very important, inside and out of the horse’s stall. Keeping your horses away from cattle and only in clean pasture is also crucial in managing this issue. 

It is important in management to regularly check the feces of your horse and to continue administering the medications as your veterinarian has prescribed.  Checking feces should be done year round, as Trichostrongylus spp also thrives in the winter season and colder weather. Your veterinarian can help with this, as well. He can also give you advice in managing parasitic infestations and how to resolve them.



Trichostrongylus spp Questions and Advice from Veterinary Professionals

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