Trichostrongylus nematodes (roundworms) are intestinal (mainly) parasites of animals, primarily ruminant mammals, including domesticated mammals such as sheep, goats, and camels. Trichostrongylus axei is among the handful of species that have been documented as sometimes infecting humans. Trichostrongylus species area found worldwide, but they are more common where livestock is raised. (Centers for Disease Control Parasites and Health website)