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Endoparasites - Trichostrongylus

Trichostrongylus axei: Stomach hair worm, bankrupt worm.

General Description: The adult worm is tiny (0.5 centimetres) and hair-like.

Life Cycle: Direct. Infective third-stage larvae are produced about 6 days after the eggs leave the host in faeces, if temperature and humidity levels are sufficiently high. Infective larvae are ingested by animals. The prepatent period is approximately 20 to 25 days.

Location: Abomasum and occasionally small intestine.

Geographical Distribution: Worldwide.

Significance: Serious weight loss and poor growth occur when animals are heavily infected especially in mixed infections with Ostertagia. Young cattle are most susceptible but infection also occurs in older animals.

Effect on Host: Adults may penetrate the lining of the abomasum, causing irritation. Wart-like swellings may occur in these areas and cause diarrhoea and reduced appetite.

Diagnostic Information: Strongyle-type eggs are found in faeces. Differential diagnosis of L3 larvae is possible.

Control: Pasture management and anthelmintic treatment of animals are important in reducing populations of infective larvae on pasture.

   
T.axei – adult male   Trichostrongylus – egg   Posterior end – female showing uterus with eggs


Trichostrongylus spp: Black scours worm, bankrupt worm.

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

Life Cycle: Typical direct nematode life cycle. Strongyle-type eggs in faeces 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.

Location: Small intestine.

Geographical Distribution: Worldwide.

Significance: 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 diarrhoea. Weakness may be the only sign of acute infection. Although clinical anaemia is not a common sign, the combined effect of emaciation, diarrhoea and malnutrition may result in anaemia. If coccidiosis accompanies trichostrongylosis, enteritis may occur.

Diagnostic Information: Strongyle-type eggs appear in faeces.

Control: 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.

 
Anterior end – trichostrongylus sp   Posterior – male T.colubriformis


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