First report of the ultra-infectious focus of Paragonimus westermani in northern suburban area of Guangzhou.

To investigate the popularity and distribution of Paragonimus westermani in northern suburban area of Guangzhou,1 216 snails and 39 crabs were collected from creeks and meanwhile,3 excretion samples from both cats and dogs from villages at the regions of investigation were also collected.The cercariae,metacercariae and eggs of P.westermani were detected from these collected samples and the adult worms were searched during autopsy of the egg-positive cats and dogs.It was found that the infection rate with P.westermani in snails was 0.32%(4/1202),while that of metacercariae in crabs was 100%(35/35) with an intensity of infection of 2-1050 metacercarae per crab and 2-30.75 metacercariae per gram of crab.Some crabs were found to be infected both with the diploid type and triploid type of P.westermani.The snails and crabs were identified to be Semisulcospira libertine and Sinopotamon pinheense respectively.Paragonimus eggs were also found in one excretion sample of cats and dogs.In the egg-positive cats and dogs,15 adult worms were found with a positive detection rate of 33.33%(2/6).It is proved for the first time that the northern suburban area of Guangzhou is the ultra-high infectious focus of P.westermani infection(Grade I).Since P.westermani is the main pathogenic paragonimus in our country and the infectious focus of this infection lies in Liuxi river where is the origin of drinking water supply for Guangzhou and Conghua,close attention should be paid to the issue.