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[Trichostrongylus spp.]

Egg of Trichostrongylus sp. in an unstained wet mount of stool. Image courtesy of the Indiana State Department of Health.

Causal Agents

Nematodes in the genus, Trichostrongylus. Although primarily parasites of animals, several species of Trichostrongylus have been known to infect humans, including T. orientalis, T. colubriformis, and T. axei.

Life Cycle

Life cycle of Trichostrongylus

Eggs are passed in the stool of the definitive host (usually a herbivorous mammal) The number 4, and under favorable conditions (moisture, warmth, shade), larvae hatch within several days. The released rhabditiform larvae grow in the soil or on vegetationl The number 1, and after 5 to 10 days (and two molts) they become filariform (third-stage) larvae that are infective The number 2. Infection of the human host occurs upon ingestion of these filariform larvae The number 3. The larvae reach the small intestine, where they reside and mature into adults. Adult worms inhabit the digestive tract of their definitive hosts and may occur as incidental infections in humans The number 5.

Geographic Distribution

Worldwide, but more common where livestock is raised.

Clinical Presentation

Most infections are asymptomatic. Heavy infections can cause gastrointestinal problems (abdominal pain, diarrhea, anorexia), headache, fatigue, anemia and eosinophilia.

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  • Page last reviewed November 29, 2013
  • Page last updated November 29, 2013
  • Content source: Global Health - Division of Parasitic Diseases and Malaria
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