Each year, hundreds of aquatic migratory birds migrate from northern hemisphere to the Mazandaran Province, northern Iran. Little information is available on prevalence and density of schistosomes in water birds in Iran and around the world. The objectives of this study were to determine definitive and intermediate hosts of avian schistosomes as well as to assess human cercarial dermatitis (HCD) in a wildlife refuge in Mazandaran Province. Of 1106 examined people, 589 (53.2%) had maculopapular rashes mainly on feet but also on hand. The majority of cases were adults and local residents. Of 260 ducks, 41 (15.8%) were found to be infected with Trichobilharzia spp. eggs or adult worms. Prevalence was highest in Anas clypeata and Anas platyrhynchos, 79% and 18.9%, respectively. A total of 1.2% snails, examined by both shedding and crushing methods, were infected with furcocercariae belonging to avian schistosomes. The most frequently infected snail was Lymnaea gedrosiana (5.9%). Our results showed that cercarial dermatitis and avian schistosomiasis is a common and yet neglected disease in this area. Anas clypeata played the most important role in exposing snails to miracidia in ponds and paddy fields. Moreover, because of the high prevalence in ducks and high prevalence of HCD in the region, it is considered as a new endemic focus in Iran.