This study was done with the objective of determining the influence of fish species and pond management practice on prevalence of parasites of tilapia and catfish farmed in Nyeri County, Kenya.

One hundred and seventeen farmers were interviewed to evaluate types of ponds used, species of fish farmed, fish culture, source of water for fish ponds and whether farmers drained and treated their fish ponds after harvesting fish. It was observed that over 53% (n=117) of farmers were using earthen ponds, 62.4 % (n=117) preferred monoculture system. The most popular source of water to either fill or replenish their fish ponds was from a river while 76.9% (n=117) did not bother to drain ponds after harvesting fish.

Using seine nets 366 (89 catfish; 277 tilapia) live fish were caught from 15 fish farms.

Of the 366 fish, 158 originated from liner ponds with 108 from earthen ponds. Different fish organs including Intestines, Eyes, Stomachs, skins, muscles and gills were observed using dissecting microscope for different parasites.

The results indicated that 115 fish were infected with different species of ectoparasites or endo-parasite in the different examined organs, giving overall prevalence of slightly over 31%. Infestation with parasites was significantly higher (p< 0.05) in Oreochromis niloticus (67.8%) than in Clarius gariepinus (32.2%). No significant difference (p > 0.05) in parasitic infestation between earthen (52.2%) and liner (48.8%) ponds.

Among the 366 fish examined in the study, 57 had Dactylogyrus spp., 30 had Clinostomum spp. metacercariae in the muscles, 10 fish were observed to habour leeches on gills while 7 fish had their eyes infested with Diplostomum spp. There were other parasites also observed in this study in fish that included Trichodina spp. (4 fish), Paracamallanus spp. (1 fish), Acanthocephala spp. (2 fish) Gyrodactylid spp. (2 fish) Contracaecum spp. (1 fish) and Gyrodactylid spp. (1 fish).

This study therefore observes that fish pond management practice (types of ponds used, species of fish farmed, fish culture, source of water for fish ponds and whether farmers drained and treated their fish ponds after harvesting fish) and fish species influence prevalence of parasites in farmed fish. These ectoparasites and endoparasites may have both economic and public health implications and a further study on their control is indicated.