Paragonimiasis, Man

Paragonimiasis is a lung fluke infection contracted by the consumption of freshwater crabs or crayfish (Paragonimus). The metacercariae penetrate the intestinal wall, migrate through the peritoneum across the diaphragm, and enter the pleural cavity to reach the lungs. The worms develop in bronchioles and when mature shed their eggs into the bronchi (Pathology, Fig. 21D). The worms elicit an exudate with neutrophilic and eosinophilic granulocytes, generally developing a cyst or an abscess which may be surrounded by a fibrous capsule. Hemorrhage into the cyst often occurs and the brownish mucoid exudate containing eggs is coughed up. Degenerating eggs give rise to a granulomatous inflammatory reaction. Aberrant sites of infection include the abdominal cavity, soft tissues, and the brain, where the birefringent Paragonimus eggs must be differentiated from the nonbirefringent schistosome eggs. In general the metabolic products of the adults give rise to microabscesses, and the...