Molecular and Histopathological study and first report of Lernaea cyprinacea infestation in Oncorhynchus mykiss in the Chaharmahal and Bakhtiari province

Abstract Many species of freshwater fish are known to be infested by the parasitic copepod Lernaea cyprinacea, which is not host-specific. Mass fish death may result from outbreaks of this ectoparasite infection. Ten dead fish were referred to the Aquatic Clinic to investigate the cause of mortality. After the initial examination and observation of the Lernaea on the skin, gills and oral cavity, symptoms such as increased mucus production, inflammation, redness and swelling at the attachment point were also observed. Lernaea were isolated from the external surface of fins, operculum and body surface of Oncorhynchus mykiss. The histopathological findings including ulceration, chronic inflammatory reaction, infiltration of inflammatory cells, degeneration and necrosis of the muscles and also head region of the parasite were detected. After performing morphological, histopathological and molecular examination, the Lernaea species was identified as L. cyprinacea. In the present study of L. cyprinacea was reported for the first time in the rainbow trout in Chaharmahal and Bakhtiyari province (Iran).