Larvas de trematódeos de Biomphalaria spp. (Gastropoda: Planorbidae) de dois municípios do leste da Amazônia Legal brasileira

OBJECTIVE: To carry out a survey about larval trematodes in Biomphalaria spp. snail biodiversity, obtained from natural breeding sites of two municipalities in Maranhao State, eastern Brazilian Legal Amazon. MATERIALS AND METHODS: The gastropods were collected bimonthly at three distinct points in Sao Luis and Sao Bento, from February 2015 to January 2016. The mollusks obtained were identified by external and internal morphology. The cercariae were fixed, stained and identified using specific taxonomic keys. RESULTS: A total of 2,661 molluscs were collected in Sao Luis and 1,726 in Sao Bento; and 3.72% (99/2,661) and 4.87% (84/1,726) of planorbids were positive for larval trematodes, respectively. In Sao Luis, the helminth fauna identified were Clinostomidae (0.41%), Diplostomidae (0.56%), Echinostomatidae (0.90%), Schistosomatidae (0.71%), Spirorchiidae (0.41%), and Strigeidae (0.71%) families; and in Sao Bento were Echinostomatidae (1.80%), Schistosomatidae (0.75%), Spirorchiidae (1.56%), and Strigeidae (0.75%) ones. Among cercariae in Schistosomatidae family of the both municipalities, only Schistosoma mansoni was reported. In Sao Luis, Biomphalaria species presented the following infection rates: 1.95% (52/2,661) for Biomphalaria straminea and 1.76% (47/2,661) for Biomphalaria glabrata. In Sao Bento, these rates were 4.46% (77/1,726) for B. glabrata and 0.40% (7/1,726) for B. straminea. CONCLUSION: The identified cercariae, with the exception of S. mansoni, are considered first reports for Sao Luis; while for Sao Bento the first report is for the Strigeidae family.