Paragonimiasis in Yongjia County, Zhejiang Province, China: clinical, parasitological and karyotypic studies on Paragonimus westermani.

Paragonimiasis in Yongjia County, Zhejiang Province, China, has been of such public health concern that a specialized Institute for Paragonimiasis Control has been established there. The study reported here involved both parasitological research on Paragonimus westermani in the endemic areas and a clinical analysis of 94 cases of paragonimiasis. Eggs were found in sputum, feces and brain tissue in 45 cases. Twenty patients, 19 of whom where children under 10 years of age, showed hepatic injury. Treatment with praziquantel or bithionol had satisfactory results in all cases. Dimensions of the parasite eggs, metacercariae from freshwater crabs and adult flukes suggested that the form of P. westermani in Yongjia is the 'small type': a suggestion supported by karyotypic studies on gonad cells from adult flukes collected from experimentally infected animals as all were found to be diploid. In conclusion, the 'small type' or diploid form of P. westermani is the cause of paragonimiasis pulmonary symptoms in Yongjia.