Prevalence of potential pathogenic and zoonotic aerobic bacteria in wild and farmed Oreochromis jipe, Oreochromis niloticus and source water in Taita-Taveta County, Kenya

Abstract

Bacterial infections can cause latent, low to high mortalities in aquaculture farms and wild fish while some bacteria may be zoonotic. This study isolated, characterized and identify potential pathogenic and zoonotic aerobic bacteria in farmed and wild Oreochromis jipe, O. niloticus, their hybrids and culture water source from Taita-Taveta County. One hundred and eleven apparently healthy-appearing fish consisting of 67 O. jipe, 34 O. niloticus and 10 hybrids and nine water (7 farms and 2 Lake Jipe) samples were processed. Samples were aseptically collected from each fish, namely, skin and kidney swabs; gills and intestinal tissues. Conventional culture, biochemical and Matrix Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry tests were done to identify isolated bacteria. A total of 596 bacterial isolates representing 22 genera were recovered from 444 fish organs and 9 water samples. Of these, the highest numbers were from the gills at 29.7% followed by skin 29.6%, intestines 24.4%, kidney 11.8% and the least from water at 4.7%. Potential fish pathogens were Bacillus cereus (8%), Aeromonas veronii (8%), Aeromonas hydrophila (5%), Lysinibacillus fusiformis (5%), Acinetobacter johnsonii (4%) and Acinetobacter solii (4%). Potential pathogenic and zoonotic bacteria isolated were Staphylococcus lentus 17.9% (5/28), Aeromonas hydrophila 10.7% (3/28) and Aeromonas hormaechei 7.1% (2/28). From the sampling site; 28.4% (169/596) of the total isolates were collected from Taveta, then Mwatate with 26.9% (160/596), Mkwajuni 16.8%, (98/596), Kenya Wildlife Service 7.0% (42/596), Wundanyi 6.7% (40/596), Voi 6.6% (39/596) and the inlet of the Lake Jipe had a 3.2% (19/596) and from the water samples 4.7% (28/596). These findings confirm that fish in aquaculture farms, wild fish and water used for aquaculture harbors potentially pathogenic and zoonotic bacteria which may cause fish diseases and pose public health risks. Extension officers and farmers need awareness on mitigation measures against these pathogens.