Trichostrongylus

Trichostrongylus species are nematodes (round worms), which are ubiquitous among herbivores worldwide, including cattle, sheep, donkeys, goats, deer, and rabbits. At least 10 Trichostrongylus species have been associated with human infections. Infections occur via ingestion of infective larvae from contaminated vegetables or water. Epidemiological studies indicate a worldwide distribution of Trichostrongylus infections in humans, with the highest prevalence rates observed in individuals from regions with poor sanitary conditions, in rural areas, or who are farmers / herders. Human infections are most prevalent in the Middle East and Asia, with a worldwide estimated prevalence of 5.5 million people.

== Life cycle == Eggs are passed through the feces of an infected definitive host, usually a mammalian herbivore including rabbits, sheep, cattle, and rodents. Under certain environmental conditions, which include optimal temperature and humidity, larvae hatch from eggs after several days. Hatched rhabditiform larvae grow on vegetation or within soil. After 5 to 10 days, two molts (L1 & L2) have occurred and the parasite becomes a filariform (L3) larvae that is infectious. Infection in mammals occurs upon ingestion of infective filariform (L3) larvae. The larvae reaches the small intestine to reside and mature into adult worms within their definitive hosts. Infections in humans may occur as incidental infections. Trichostrongylus consists of multiple species that relate to each of its host, when it comes to parasitic survival and infection. For example, Trichostrongylus affinis primarily infects cottontail rats, Trichostrongylus sigmodontis affects hispid cotton rat, and marsh rice rat, and Trichostrongylus retortaeformis primarily affects European rabbits (Oryctolagus cuniculus).