Physella acuta Confirmed as Intermediate Host of Posthodiplostomum sp. from Lake Alqueva, Portugal

Physella acuta is an invasive freshwater snail with a global distribution and a recognized role as an intermediate host for various trematodes, including Echinostoma spp. and Trichobilharzia physellae. In Portugal, P. acuta is commonly found in freshwater bodies such as Lake Alqueva, the largest artificial reservoir in Europe. The lake’s creation has altered local ecosystems, influencing freshwater snail populations and migratory bird activity, which may contribute to the dispersal of trematode parasites. While P. acuta is present in the region, its role in trematode transmission remains unclear. This study investigated P. acuta as a potential intermediate host for trematodes in Lake Alqueva. Freshwater snails were collected from 18 sites, with cercarial shedding induced under artificial light. Infected snails were found in 2 of the 18 snail populations surveyed. A sequence analysis of the amplified ITS2 rDNA region confirmed the presence of Posthodiplostomum sp., implicating, for the first time, P. acuta as an intermediate host for this parasite in Portugal. This study highlights the need for further research on P. acuta’s role in trematode transmission and potential impact on local ecosystems to assess parasitic risks to veterinary and public health.