Preliminary Survey of Gram-Negative Bacterial Pathogens from Commonly Caught Fish Species (Oreochromis niloticus, Cyprinus carpio and Clarias gariepinus) in Lake Hayiq, Ethiopia

Abstract

A cross-sectional study was conducted from October 2016 to May 2017 on Oreochromis niloticus, Cyprinus carpio and Clarias gariepinus fish species at Lake Hayiq, North East Ethiopia with the objective of isolation and identification of major gram-negative bacterial pathogens of commonly catched fish species from Lake Hayik. A total of 98 live fishes (49 Oreochromis niloticus, 30 Cyprinus carpio and 19 Clarias gariepinus) were collected and transported to the laboratory. From the three fish species a total of 384 organ samples (96 skins, 98 gills, 94 intestines, 33 swim bladders, 19 kidneys, and 44 livers) were taken. A systematic random sampling technique was used to select the fish samples after drawn from the water. Among 384 fish organ samples 116 (30.2%) gram negative bacterial isolates were found: 9 (2.3%) Aeromonas species, 24 (6.3%) Pseudomonas species, 6 (1.6%) Enterobacter species, 29 (7.6%) Escherichia species, 4 (1.6%) Edwardsiella species, 11 (2.9%) Klebsiella species, 5 (1.3%) Proteus species, 8 (2.1%) Vibrio species, 14 (3.6%) Flavobacter species and 6 (1.6%) Salmonella species were found. Isolation among organs: Pseudomonas species, skin (33.3%), intestine (33.3%), and swim bladder (12.5%); Escherichia species: intestine (41.4%), skin (24.2%) and gill (24.2%) and Klebsiella species: liver (27.3%), gills (36.4%) were found. All the isolated bacterial species were gram-negative bacteria. From the three fish species, Oreochromis niloticus was the most affected fish species (48.2%) while Clarias gariepinus species were the least affected species (17.2%). In conclusion, majorities of those pathogens isolated and identified were very important for different fish disease outbreaks and also public health importance. But, very few and disintegrated studies with scanty data have been done whereas, it has been nowadays fishery is one of the main growth transformation plan for food security in Ethiopia. Therefore, it needs further integrated investigation on fish bacterial diseases.