Epidemiological Investigation on Intermediate Hosts of Paragonimus in Ninghai County in 2004

Objective To investigate the infections and distribution of intermediate hosts of paragonimus including crabs and snails,to observe their habits and to estimate the risk of people's infection with paragonimus.Methods Crabs and snails were collected from the spots.Their ecological environment and behavior were observed.The crabs were weighed and treated with regular precipitation method and the precipitates were examined under microscopy.Results Total number of crabs was 97.Out of crabs weighed over 5g,there were nine positive crabs with the infective rate of 11.7%.The infective rate was associated with the weight of crabs.Crabs weighing between 15g and 25g had the highest rate to 20.0%,but no snails were found in crabs weighing between 25g and 35g.20 small crabs(weighing lower than 5g) were divided into four groups and two positive groups were found.No cercariae were found in 200 snails.The intermediate hosts of paragonimus lived in clear streams with rich oxygen.Streams with slow water flows or relative immobile were more suitable for their survival.They ofen breed in the middle and upper segment of rivers.Conclusions Local people are still in danger of infection with paragonimus,so the government and the department of sanitation should keep on making effort and taking measures to prevent people from paragonimus infection and treat paragonimiass actively.