Trichostrongylus species are nematodes of cosmopolitan distribution usually found in herbivores.  However, some species can be found in humans.

Life cycle and morphology

Trichostrongylus species are small nematode worms similar to those of hookworm.  However, unlike adult hookworm, the adult worms of Trichostrongylus have no characteristic mouth parts, i.e. have no teeth or cutting plates.

Humans are usually infected with Trichostrongylus by the ingestion of the infective 3^rd stage larvae on plant vegetation whereas infection by Hookworm is through skin penetration.  Trichostrongylus mature in the small intestine in 3 – 4 weeks without any migratory pathway through the lungs.  hookworm, on the other hand mature in the intestine after migrating through the lungs.  Both adult hookworm and Trichostrongylus species attach themselves to the mucosa of the small intestine.

The eggs of Trichostrongylus are very similar to those of hookworm but are larger with more pointed ends. The eggs of hookworm measure 56 – 75µm by 36 – 40µm and those of Trichostrongylus measure 73 - 95 µm by 40 - 50µm.   Thus it is essential to use an eyepiece graticule to distinguish between the two eggs.

Clinical Disease

Symptoms are similar to those of Hookworm and are  related to the worm burden.  Several hundred worms must be present before symptoms become significant. Light infections may be asymptomatic.

Diagnosis

Definitive diagnosis is made by finding the characteristic eggs in stool specimens.  Hatched larvae may also be found and these must be distinguished between rhabditiform larvae of hookworm and Strongyloides stercoralis.  The 1^st stage larvae of Strongyloides have a short buccal cavity whereas both Hookworm and Trichostrongylus have a long buccal cavity.  However, Trichostrongylus has a characteristic beadlike swelling at the tip of its tail.

An ovum of Trichostrongylius species