Biomphalaria straminea as an Intermediate Host of a Renal Trematode Species of the Genus Tanaisia (Trematoda: Eucotylidae) in Brazil

Purpose Eucotylid trematodes are parasites of the urinary system of birds with a cosmopolitan distribution. Despite the importance of these flukes, fundamental aspects of their biology, such as intermediate hosts and larval morphology, are poorly known. Herein, the potential involvement of aquatic mollusks in the transmission of a species of Tanaisia is reported for the first time. Methods During the search of non-emergent larval stages of trematodes in mollusks collected from an urban waterbody from Brazil in February of 2021, 1 out of 18 specimens (5.5%) of Biomphalaria straminea was found harboring sporocysts, cercariae and encysted metacercariae morphologically compatible with those described for eucotylid species. Sequences generated for 28S, ITS-2, and cox 1 molecular markers were compared with sequences available in GenBank and subjected to phylogenetic analyses. Results Molecular analyses revealed parasite affiliation with members of the genus Tanaisia, given it groped in a strongly supported clade with species of this genus included in the 28S phylogenetic tree. The larvae tentatively identified as Tanaisia sp. can be conspecific with an unpublished isolate of Tanaisia valida found in birds in South Brazil (100% similarity in 28S and ITS-2). Conclusion Biomphalaria straminea is reported as a natural host of a species of Tanaisia for the first time. This finding highlights the possibility, so far unknown, of transmission of species of the family Eucotylidae in aquatic environments.