Occurrence and effect of Diplostomum parasites in cultured Oreochromis niloticus (L.) and distribution in vector snails within Kisumu City, western Kenya

Freshwater snails and larval trematode communities were studied in relation to diplostomiasis infection in fish. Out of 680 fish examined, 52.2% were positive for Diplostomum parasites. Lymnea, Biomphalaria, Bulinus and Ceratophallus snail species occurred, however Diplostomum larvae were only in Biomphalaria at a prevalence rate of 21.69%. There was no significant relationship between parasite abundance and fish condition factor in all the study sites, hence the wellbeing of the fish was not compromised by the parasites. Values of the regression co-efficient obtained for the length–body weight relationship in all the farms suggested isometric growth.