Preliminary study of the prevalence of helminths and their associated pathological lesions in four fish species from River Tana

Abstract

A preliminary study was carried out between January and May 2006 to investigate the prevalence of helminths and their pathological lesions in four species of fish. A total of 43 fresh fish from the Tana River, sold at the Gikomba market, were purchased and autopsied. These fish were 15/43 (34.9%) of the Oreochromis species, 11/43 (25.6%) Clarias spp., 10/43 (23.2%) Cyprinus carpio and 7/43 (16.3 %) Barbus spp. At necropsy, several Contraceacum worms in the third instar larvae were found in the abdominal cavity, muscles and behind the gills. A total of 91% of catfish (Clarias spp.) And 20% of tilapia (Oreochromis spp.) Had a “moderate to severe” infestation of Contraceacum worms. The intensity of the infestation varied between 1 and 593 helminths per fish, which caused severe peritonitis and adhesion to visceral organs. Under the microscope, helminths caused heavy infiltration of heterophiles, macrophages, plasma cells and organ fibrosis. There was pressure atrophy of the bile duct epithelium in a tilapia, which was caused by a migratory pleurocercoid tapeworm, a Cryptocotyl protozoan embedded on the gill arch, and granulomatous parasitic lesions on the walls of the intestines. Other lesions observed were hemorrhages, ulcers and wounds on the fins, around the mouth and on the skin. The results of this study show that the fish of the Tana River are infested with helminths which cause serious pathological lesions in the affected fish.