Occurrence of a Snail Borne Disease, Cercarial Dermatitis (Swim¬mer Itch) in Doon Valley (Uttarakhand), India

‘Cercarial dermatitis’ also known as swimmers itch (Skin allergies) is caused by a trematode parasite, Schistosoma which has two hosts - an invertebrate (snail) and a vertebrate (livestock, human being). Although the availability of both vector snails and pathogens at the selected site the Doon Valley in northern India has already been confirmed but there was a hazy picture of the disease, whether it is due to entrance of cercariae or due to wild variety of grass (Parthenium hysterophorus).The present study is an attempt to provide a way forward towards the vector snails and snail borne diseases in the study area. Snail sampling and identification was done by applying standard methods / using Keys & Catalogues. Associated parasites and cercariometry in snails has been worked out by cercarial shedding. Human involvement at zoonotic level has been performed in collaboration with Health centers and socio- economic aspect of inhabitants of study area. The snail diversity encountered 19 species including the vector species such as Indoplanorbis exustus, Gyraulus convexiusculus, Melanoides tuberculata and Lymnaea acuminata. The cercarial diversity comprised Furcocercous, Monostome, Amphistome and liver fluke / Xiphidiocercaria. During the study (2009-2010), 0.173% was found with cercarial dermatitis among human population in the selected area. The symptoms of disease recorded were red spots and swellings on effected parts of skin. Frequent visits of livestock to the water body and presence of vector snails provides a clue in completing the life cycle of the parasite of the family Schistosomatidae. Cercarial dermatitis has been considered a potential risk at those places where warm blooded and snail’s hosts share a link with aquatic bodies with particular emphasis to temperature and time of year.