Atlas of livestock parasites
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Trichostrongylus spp.



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Trichostrongylus spp.
Hair worm, bankrupt worm, black scours worm

General Description:
Thin, reddish-brown nematodes up to 5.5 mm long. Males have bursae with large lateral lobes.

Life Cycle:

Typical direct nematode life cycle. Strongyle-type eggs in feces are thin-shelled. Infective larvae develop in a minimum of 4 to 6 days; much longer periods are required in cool temperatures. Third-stage larvae may survive 4 to 6 months on pasture. Infection occurs by ingestion; the developing larvae burrow superficially into the crypts of the mucosa. The prepatent period is 20 to 25 days.

Small intestine.

Geographical Distribution:

Losses from Trichostrongylus species infections are not easy to measure. Trichostrongylus is commonly present in mixed-species infections, so its effect is additive.

Effect on Host:

Weakness and death can occur in young animals when heavily infected. This may be acute if the infection occurs over a short period of time. In chronic infections, wasting can occur along with constipation or diarrhea. Weakness may be the only sign of acute infection. Although clinical anemia is not a common sign, the combined effect of emaciation, diarrhea and malnutrition may result in anemia. If coccidiosis accompanies trichostrongylosis, enteritis may occur.

Diagnostic Information:
Strongyle-type eggs appear in feces.

Trichostrongylus spp. egg
Approximately 80 µm long
Broad ellipse
Barrel-shaped side walls
Blastomeres present, number vary
It is not often possible to identify strongyle eggs to genus level as the eggs of most strongylid and trichostrongylid species are similar in appearance and overlapping in size.
If identification is necessary the faecal sample must be cultured to provide L3 larvae for further examination !!!


Pasture management can be used to reduce Trichostrongylus larvae on pasture. Immunity develops to Trichostrongylus, and self-cure may result after a period of infection. Anthelmintics may be used to treat such animals while they are still susceptible to damage by the parasite.


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