Oesophagostomum dentatum, O. brevicaudum, O. quadrispinulatum: Nodular worm

General Description: Adult nodular worms are 8 to 14mm long, are white, and have a shallow buccal capsule.

Life Cycle: The infective, ensheathed, third-stage larvae develop in a week from eggs shed in the faeces. After ingestion by pigs, the larvae cast off their sheaths and burrow into the intestinal mucosa anywhere between the pylorus and the rectum. After 5 to 7 days, the larvae moult to the fourth stage in the mucosa. Then the larvae emerge into the intestinal lumen, mature, and begin to lay eggs about 40 to 50 days after infection.

Location: Adult worms in large intestine; larvae in wall and large intestine.

Geographical Distribution: Worldwide.

Significance: The highly prevalent nodular worm causes decreased feed efficiency and outright illness. If regular treatment of pig herds for the battery of common intestinal worms is not practiced, this parasite will be a major contributor to subsequent economic losses.

Effect on Host: The major damage occurs when larval worms emerge from the intestinal mucosa, seriously eroding the intestinal lining. Animals which have been previously infected form nodular swellings up to 1cm in diameter around each larva in the mucosa. The larvae remain in the nodules for about 3 months before breaking into the gut lumen. Many larvae die within the nodules, which then become hardened. The presence of numerous nodules interferes with intestinal motility and absorption. Heavy first infections may be characterised by severe diarrhoea of sudden onset, often dark in colour and containing a great deal of mucus. This can result in exhaustion and death within 3 to 4 weeks. The nodules' interference with intestinal function produces intermittent diarrhoea, loss of appetite, and emaciation. Pigs that survive these infections are usually stunted in growth.

Diagnostic Information: The eggs of Oesophagostomum can not be differentiated from those of Hyostrongylus and Trichostrongylus. More commonly, diagnosis is made by differentiation of third stage larvae or at postmortem examination by the presence of adult worms and nodules in the bowel.

Control: General nematode control measures as described in the Overview are applicable to nodular worm management. A complicating factor is the fact that larvae within nodules are not affected by commonly used anthelmintics. Therefore, repeated treatments several months apart are necessary to insure eradication.

Oesophagostomum adult anterior end		Oesophagostumum close up of mouth parts
Nodules in the intestine		Male and female Oesophagostomum spp. in copulation