Determination of definitive and intermediate hosts of cercarial dermatitis-producing agents in northern Iran.

BACKGROUND The study concerns the prevalence of avian schistosomes in intermediate and definite hosts in Mazandaran Province, northern Iran. METHODS A total of 14190 fresh-water snails belonging to various genera were sampled and tested for cercarial emission by lighting and then crushing. During the same period, the nasal blood vessels and mesenteric veins of aquatic birds, mainly belonging to the Anatidae family, were examined under dissecting microscope for detecting adult worms. RESULTS Forty-seven (0.33%) of examined snails mainly Lymnaea gedrosiana, L.palustris, L.stagnalis, and Planorbis planorbis were found to be infected with larval stages of Trichobilharzia spp. Adult schistosomes were observed in 25 (18.1%) wild waterfowls. The most infected birds were Anas platyrhynchos, A.clypeata, and Aythya ferina, respectively. CONCLUSION Annually migration of various species of aquatic birds toward the northern parts of Iran and the simultaneous presence of intermediate snails in the water resources of this area, combined with long hours of sunshine in the summer months, suggest that cercarial dermatitis could be a prominent health problem, especially among paddy field workers in this area.