Habronema spp Infection in Horses

Last Updated on March 29, 2022 by Allison Price

Habronema mucae and H microstoma infect the stomach’s mucosal lining and can cause catarrhal gastritis. Draschia may cause tumor-like swellings at the margo plicatus. However, this parasite is now rare in domestic horses. Habronema parasites are rarely found in the gastric stage. Their most prominent manifestation is the cutaneous condition commonly called summer sores. Although anthelmintic efficacy against these parasites has not been evaluated in recent years, macrocyclic lactones have still been shown to be effective against their gastric stages.

Habronema spp Infection in Horses

Habronema , Draschiaspp vector-borne parasites that use muscid flies to their intermediate hosts are Habronema . Adult parasites are formed in the stomach when they ingest larvae that have been deposited around the mouth by flies or dead flies. In about 8 weeks, the parasites will become adults within the stomach. Although adult Habronema can be found in close proximity to the gastric mucosa they do not cause any clinical problems. Draschiasp is a rare breed in domestic horses.

Clinical Signs

Although the gastric stage of Habronemaspp has been shown to cause catarrhal gastritis (a gastric manifestation), clinical manifestations have not yet been reported. Similar to the pulmonary form, habronemiasis is also described. However, it’s unclear what the clinical implications might be.

Draschiasp is a condition that causes large fibrous masses to be found near the margo-plicatus. However, the clinical significance of these lesions is unknown and they are rare.


Because eggs are hard to see under a microscope, fecal flotations and fecal count are not reliable methods to diagnose Habronemaspp gastric infections. Adult worms measure 6-25mm in length, so could they be diagnosed via gastroscopy, or gastric lavage? However, this has not been documented.


Although there are no anthelmintic efficacy trials, the gastric stages in Habronemaspp should be susceptible to macrocyclic lactone treatment.


Although fly control may theoretically reduce the parasite’s infection pressure, it has not been experimentally tested.

Zoonotic Risk


The Key Points

  • Habronemaspp is thought to be quite common in domestic horses.
  • The clinical implications of gastric stages are not known.
  • It is not easy to diagnose an antemortem.
  • Macrocyclic lactones may be useful against gastric stages.
Allison Price
Allison Price

I’m Allison, born and raised in San Diego California, the earliest memory I have with horses was at my grandfather’s farm. I used to sit at the stable as a kid and hang out with my Papa while he was training the horses. When I was invited to watch a horse riding competition, I got so fascinated with riding!