[Survey on the foci of Paragonimus in Youxi, Yongtai and Pinghe Counties of Fujian Province].

Objective: To investigate the natural foci of paragonimiasis in Youxi, Yongtai and Pinghe Counties of Fujian Province.
Methods: One village each from the three counties was selected according to reported paragonimiasis cases. Freshwater snails collected from fields were examined for cercariae. Freshwater crabs obtained in the fields were examined for metacercariae by washing filtration method or direct compression method. Feces of cats and dogs were collected for the detection of eggs by water precipitation. In order to identify the species of Paragonimus, 4 cats were orally fed with metacercariae. At the same time, the habitat of three survey sites was observed.
Results: Three fluke species, namely, P. skrjabini, P. westermani and P. cenocopiosus(Syn. Euparagonimus cenocopiosus) were found. In Banlin Village of Youxi County and Chishui Village of Yongtai County, the seropositive rate by IgG ELISA were 6.8% (21/309) and 6.8% (9/133), respectively. Four species of freshwater snails were found, two species of Tricula and one species of Pseudobythinella were newly identified first intermediate hosts of Paragonimus. Four species of freshwater carbs were found, one species of Nanhaipotamon served as a new second intermediate host of Paragonimus. In Youxi, the infection rate of P. skrjabini cercariae in snails and metacercariae in crabs was 2.1% (27/1 344) and 92.1% (58/63), respectively; the index of crab infection and the positive ratio of Paragonimus eggs in cat feces was 171.91 and 1/7, respectively. In Yongtai, the cercariae infection rate in Pseudobythinella and Tricula snails infected with P. skrjabini was 0.6% (4/690) and 0.1% (2/ 2330), respectively; the infection rate of P. skrjabini metacercariae in crabs was 18.2% (18/99); the index of crab infection was 9.12. In Pinghe, the infection rate of cercariae in Semisulcospira libertina and metacercariae in crabs was 03% (3/1092) and 44.9% (35/78), respectively; the index of crab infection was 616.
Conclusion: Paragonimus skrjabini P. westermani and P. cenocopiosus have been found from the three counties of Fujian Province with different infection level in snails and crabs.