Prevalence of Cercariae Infection in Snails From the Lymnaeidae and Physidae Families in Aquatic Regions of Guilan Province, Northern Iran, and the Effect of Some Physicochemical Parameters of Water on Snail Abundance and Infection Rate

Background: Some freshwater snails are as intermediate hosts of human and animal parasitic trematode. Study on freshwater snails’ fauna and cercariae infection play important role to detect sources of infection. Objective: The aim of the present study was to determine diversity and cercariae infection of Lymnaeidae and Physidae freshwater snails and effects of physicochemical parameters of water on their abundance and distribution in Guilan province, North of Iran. Methods: Over one year, a total of 117 regions in Guilan province were investigated for Lymnaeidae and Physidae freshwater snails and identified. Water samples of each region was also collected for physicochemical analyses. Identified snails were examined for cercariae infection by shedding method. Results: Of 39,486 collected snails, three species of two genera including 19,726 Lymnaea auricularia (49.96%), 4911 L. palustris (12.44%), and 14849 Physa acuta (37.6%) were identified. Cercariae infection rate was 2.36%. Identified cercariae were xiphidiocercariae (0.94%), echinostome (0.8%), furcocercous (0.44%), lophocercous (0.16%), and gymnocephalous (0.02%). The highest infection rate was in spring (3.37%). Temperature and pH had inverse effect and salinity and water electrical conductivity had direct effects on snails’ density. Conclusion: Two genera of Lymnaea and Physa exist in examined aquatic habitats of Guilan province, North of Iran in different seasons of a year. The physicochemical parameters of water had effects on distribution and snails’ density and also abundance of cercariae infection in them.