Contamination of Vector Snails with the Larval Stages of Trematodes in Selected Areas in Northern Iran

Background: Identification of freshwater snails and possible trematodes transmission sites are essential to continue monitoring the potential for disease outbreaks in areas with a history of parasitic infections. We aimed to search some areas in the margin of the Caspian Sea, northern Iran to identify the snail fauna of this area and verify the contamination of vector snails. Methods: More than 5,308 snails from 51 diverse and permanent habitats were studied from April 2019 to October 2021. Snails were collected randomly and identified using shell morphology. Trematode infection in snails was investigated by the release of cercariae and dissection methods. Results: Five families of freshwater snails including Lymnaeidae, Physidae, Planorbidae, Bithyniidae, and Viviparidae were investigated in the Caspian Sae Litoral of Iran. Physidae were found as the most prevalent snails (55.1%) followed by Lymnaeidae (29.4%). The parasitize rate was observed as 20% using releasing cercaria technique. Echinostomatoidea (31%), Schistosomatoidea (8%), and Diplostomoidea (21%), and Plagiorchioidea (40%) were seen as detected parasites. Meanwhile, 60% of the studied snails illustrated the other stages of trematodes. Conclusion: The rate of infection of snails with different cercaria in northern Iran is significant. It needs further deep studies to clarify the situation of zoonoses transmitted by snails in the region. Policy makers should pay attention more to this area in terms of monitoring the snail-transmitted diseases.

Automated summary

This study investigated the snail fauna in the margin of the Caspian Sea in northern Iran, revealing five different families of freshwater snails. Physidae and Lymnaeidae were the most prevalent snails. Trematode infection was observed in 20% of the studied snails using cercariae release technique, with Echinostomatoidea, Schistosomatoidea, Diplostomoidea, and Plagiorchioidea as the detected parasites. Additionally, other stages of trematodes were found in 60% of the snails.