Oesophagostomum radiatum: Nodular worm.

General Description: Adult worms are stout bodied and 14 to 22cm long.

Life Cycle: Adults in the intestine lay eggs which are passed in faeces. Hatching produces larvae which pass through two moults, reaching the infective third-larvae stage in approximately 7 days. When ingested with herbage, the larvae penetrate the wall of the host´s intestine, forming nodules anywhere between the stomach and the rectum. After 5 to 7 days they return to the intestinal lumen and travel to the colon, where they undergo a final moult and mature into adults. Eggs appear in the faeces about 41 days after the larvae are ingested.

Location: Larvae in nodules in stomach and small and large intestines; adult worms in large intestine.

Geographical Distribution: Worldwide in wet, temperate climates.

Significance: Oesophagostomum, when present in large numbers, is one of the worms most damaging to cattle. Young stock in particular are seriously affected and may die from nodular worm infections.

Effect on Host: Infective larvae burrow into the intestinal wall; following initial infection and in reaction to them the host forms pea-sized nodules known as granulomas. Granulomas impair intestinal function, particularly fluid absorption. The result is black, foul-smelling diarrhoea, which is very debilitating. The disease oesophagostomiasis is characterised by anaemia and oedema in addition to the explosive diarrhoea.

Diagnostic Information: Thin-shelled, strongyle-type eggs appear in the faeces. The finding of pea-sized nodules in the intestinal wall at necropsy indicates oesophagostomiasis.

Control: Pasture management; drenching cattle and the administration of an anthelmintic.

Oesophagostomum – adult, anterior end		Nodules in intestinal wall