Discussion of PCR detection method and investigation of

Abstract

Aiming at the problem of difficult detection of sedentarius ciliates, unclear pollution sources and difficult identification of species in the cold-water fish farming, the major parasitic species of the parasites and the infective factors were investigated and analyzed. Samples of cold-water fish and water were collected in different seasons in Hebei Province. Firstly, the sedentarius ciliates on the fish body and in the water environment were initially identified by using morphology. Secondly, a PCR method was established for molecular level identification and phylogenetic analysis. Finally, the reasons for cold-water fish infecting the parasite were analyzed. Morphological identification reveals that the mainly parasitic species of sedentarius ciliates were Epistylis sp. and Vorticella sp.; A PCR method to test the parasites is successfully established. The results of sequences alignment and phylogenetic analysis verify the correctness of morphological test. The established PCR method is used to detect the prevalence of sessile ciliates in the water environment, which is as high as 94.38%, and the infection rate of the fish is up to 100% with no seasonal difference. The parasites in water may be one of the reasons for the long-term infection of the fish. The findings provide a scientific basis for predicting, preventing and treating cold-water fish diseases, as well as serving as a reference for disease prevention and control in the sustainable development of the cold-water fish farming industry.

Keywords

• animal parasitology; cold-water fish; sedentarius ciliate; morphology; phylogenetic analysis