Molecular Detection and Subtype Distribution of Blastocystis sp. in Cold-water Fish and cultured water

Blastocystis sp. is a eukaryotic protozoan parasite reported in patients with diarrhea and irritable bowel syndrome. So far, it has been determined the parasite occurs in the intestinal tract of humans and animals worldwide. However, few studies have investigated the distribution of Blastocystis sp. in cold-water fish and cultured water. After DNA extraction of tissue and water samples, a polymerase chain reaction (PCR) assay was established to detect Blastocystis sp. The results showed the detection rate of the parasite was 3.70% in the tissue samples and 6.29% in water samples. Only the ST1 subtype was in fish, but five subtypes, ST1, ST2, ST10, ST21, and ST24, were detected in water samples. There were no significant differences in the water distribution rate of Blastocystis sp. The presence of Blastocystis sp. was detected in the intestinal digesta of cold-water fish for the first time in this study, which hinted that Blastocystis sp. may infect cold-water fish. It is speculated that Blastocystis sp. entered the intestinal tract of fish with feeding and water flow. The results will provide data support for ecological prevention and control of cold-water fish diseases and lay a foundation for the formulation of sustainable aquaculture development strategies.