Trichostrongylus axei, the stomach hair worm, is a trichostrongylid parasite infecting a variety of hosts, including sheep, goats, cattle, and horses. Human infections have been described as well. The environmental life cycle is similar to cyathostomins, with the third stage larva being the infective stage. Once ingested, the larvae penetrate the gastric mucosa and develop into adult worms and emerge into the gastric lumen. Egg production begins 3–4 weeks after infection.
The parasite is seldom encountered in domestic horses and is not considered a primary parasitic pathogen.
Although no recent anthelmintic efficacy studies exist, T axei is expected to be susceptible to macrocyclic lactone (ivermectin or moxidectin) or benzimidazole (fenbendazole or oxibendazole) treatment. Benzimidazole resistance has been reported in T axei infecting sheep, so this could also occur in horses.
Also see pet health content regarding small stomach worms in horses.