Abstract:

Objective To identify the morphological and molecular characteristics of cercariae in the snail Oncomelania hupensis from outdoor feeding base in Anhui Province, and to understand their species classification for molecular biological basis in identification and control of the parasitic trematodes in local snails. Methods By systematic sampling, we obtained the snails at the end of April 2023 from an outdoor feeding base in Anhui Province. Then the samples were crushed to undergo microscopic examination of the presence of cercariae for screening positive snails. Genomic DNA was extracted from the cercariae, and the internal transcribed spacer 2 (ITS2) gene of cercaria was amplified using PCR, and then cloned and sequenced. The sequencing results were aligned with the genes in the GenBank using Basic Local Alignment Search Tool (BLAST). Finally, phylogenetic tree was constructed to analyze the species of parasitic fluke cercaria. Results A total of 300 snails were tested, with 12 testing positive. By the morphological characteristics, the parasitic cercariae fell into three forms, i.e., non-forked long-tailed, non-forked short-tailed and double-forked, which were present in 2, 1 and 9 of the positive snails, respectively. Molecular identification based on the ITS2 gene revealed that the homology of the non-forked long-tailed cercaria was 93.04% with Cryptocotyle lingua, belonging to the genus Cryptocotyle within the family Heterophyidae. The non-forked short-tailed cercaria showed 98.02% homology with Pycnoporus heteroporus and was classified as a trematode of the genus Pycnoporus within the family Lecithodendriidae, and the double-forked cercarial had a homology of 99.62%-100.00% with Schistosoma japonicum, which was Schistosoma japonicum. Conclusion In addition to Schistosoma japonicum, the Oncomelania hupensis in Anhui Province may also be intermediate hosts for Cryptocotyle sp. and Pycnoporus sp.

Key words: Oncomelania hupensis, Trematode, Cercaria, ITS2 gene, Anhui Province