Implications of heavy infestation of Lernaea cyprinacea (Crustacea: Copepoda) of Silver carp, Hypophthalmichthys molitrix at Manzala area, with trial for control using Trichlorfon

Abstract

An outbreak of heavy infestation of Crustacean parasite, Lernaea sp. has occurred autumn 2015 with heavy losses of cultured fish in Manzala area, Egypt. In this study, parasitological examination was done on about five hundred (500) earthen pond cultured Silver carp fingerlings, with body weight averaged (2-3 g), from intensive culture at Lake Manzala, for surveillance and detection of the infested Lernea sp. Clinical signs, postmortem (pm), and histopathological findings were determined. Also, the infestation rate was evaluated in relation to the physico-chemical water quality parameters. Furthermore, a trial of treatment using Trichlorfon 80% powder in a dose rate of 0.5 ppm three successive times with 10 days interval was investigated. The results revealed that (320) specimens were found to be infested with Lernaea cyprinacea, about (64%) of the total examined fish. Infested fish were off-food, restlessness, anemic, rubbing themselves against hard objects, accumulated at the water inlet, abnormal swimming and severe respiratory manifestation. Additionally, the infested L. cyprinacea was seen by naked eye remain attached to the body, fins and gills, with hemorrhagic ulcers has a button shape with elevated border were found at the point of attachment. There is no any postmortem examination. The results of water quality parameter revealed increased levels of Nitrite (0.2ppm), total ammonia (0.15ppm), H2S (0.2 ppm), dissolved oxygen (7 mg/l) and with alkaline pH. The results also showed reduction in fish mortalities with no any detectable Lernea sp. on fish surface. It can be concluded that the infestation rate of Lerneosis was elevated with poor water quality and Trichlorfon can effectively eradicate L. cyprinidae from the infested fish.