Abstract:
The study assessed the health of Nile tilapia (Oreochromis niloticus) in the Winam Gulf in Kisumu and
Homa Bay, Kenya, using descriptive lesions and histopathological semi-quantitative tools. The condition factor and
hepatosomatic index were calculated based on the total fish weight, standard length, and liver weight. The liver, gills,
and kidneys were collected from freshly killed fish, fixed in 10% buffered formalin, and processed using standard
histopathological techniques. The overall condition factor of fish was 1.12 in Kisumu while those in Homa Bay
ranged between 1.23 to 1.32 and the differences was statistically significant (p<0.05). The mean organ indices were
higher in Kisumu (liver: 4.27, gill: 3.64 and kidney: 4.47) compared to Homa Bay’s (liver: 2.26, gill: 3.21 and
kidney: 1.98). The most prevalent histopathological lesions in the liver were increased melanomacrophages centres
aggregation (12.5%), hepatocellular fibrosis (9.7%), fatty liver degeneration (10.4%) and hepatocytic necrosis (9%).
Those in gills, were leucocytic infiltration (12.5%), gill epithelial necrosis (11.8%), telangiectasia (11.1%), and gill
lamellar fusion (11.1%). In the kidney the lesions were glomerular vacuolation and dilatation of the Bowman’s
capsule (12.5%), and vacuolation and hydropic degeneration of renal tubular epithelium (11.8%). The study
provides insight into the health status of fish in Kisumu and Homa Bay and demonstrates the histopathological
changes and semi-quantitative scores of lesions in tissues caused by exposure to pollutants, infections by pathogenic
microorganisms, and other factors that compromise the health of the fish. The findings indicate a need for
monitoring the wild fish health and water pollution levels for socio-economic development and overall ecosystem
protection in the region.
