Nematodes of the genus Oesophagostomum (O. bifurcum, O. aculeatum, O. stephanostomum) are widely distributed intestinal worms of monkeys. In some regions humans are accidental final hosts. Foci of Oesophagostomum bifurcum infections occur commonly in parts of West Africa (Northern Ghana and Togo) with very high prevalence in some villages. The eggs are morphologically identical to those of hookworms. The larvae develop when the eggs land on the ground, progressing through stages 1-3 in 5 to 7 days. Probably a number of stage 3 larvae can resist long periods of dehydration. Stage 3 larvae are swallowed with food or water and penetrate the human intestinal wall. They then develop further inducing abscesses with a necrotic content (helminthoma). The worms may cause severe intestinal lesions, including eosinophilic granulomas in the intestinal wall (mostly caecum) and mesentery, deep abscesses and peritonitis. Epigastric or periumbilical masses may result.
As soon as the worms become adult they return to the intestinal lumen where they attach to the mucosa and mate. Adult worms in the intestinal lumen do not cause illness. In veterinary medicine the illness is known as “pimply gut” which refers to countless abscesses under the serosa.