Occurrence of potential pathogenic and zoonotic bacteria in farmed fish in Machakos and Nyandarua Counties, Kenya

Abstract

Bacteria can cause diseases in cultured fish. Some are zoonotic hence of public health significance. This study determined occurrence of potential fish pathogens and zoonotic bacteria in farmed fish in Machakos and Nyandarua counties. A cross-sectional study was done. Gills, intestines, skin swabs and kidney swabs from 75 fish and 15 source pond water samples were processed for bacterial culture and identification. These included 40 fish and 8 water samples from Machakos and 35 fish and 7 water samples from Nyandarua. Using conventional methods and Matrix assisted laser desorption/ionization- time of flight mass spectrometry, bacteria isolates were identified. A total of 322 bacterial isolates were identified, 182 from Machakos and 140 from Nyandarua, 299 from fish and 23 from water .They comprised 16 different bacteria genera and 20 species. Aeromonas was the most isolated bacterial genus at 32%, Bacillus 29%, Pseudomonas 21%, Flavobacterium 6%, Micrococcus 2.8% and Acinetobacter 2%,. Fish pathogen genera identified were Aeromonas, Pseudomonas, Flavobacterium, Enterococcus, Micrococcus, Enterobacter and Citrobacter. Zoonotic bacteria isolated were Aeromonas hydrophila, Aeromonas veronii, Escherichia coli, Pseudomonas putida, Bacillus cereus, Citrobacter freundii, Hafnia alvei and Enterobacter cloaca. The highest proportion of isolates was from tilapia at 59%, followed by catfish at 35.5% and rainbow trout at 7.5%. Catfish had highest number of zoonotic bacteria genera (6), tilapia (5) and trout (3). Conclusively, fish from both counties harbor zoonotic and pathogenic bacteria which can cause fish and human illnesses. Awareness creation among farmers is paramount. Study data will help in policy development on prevention and control of the respective bacteria.