Studies on occurrence of protozoan and helminth parasites in Nile tilapia (Oreochromis niloticus l.) from Central and Eastern Provinces, Kenya

Abstract

Aquaculture is an important food contributor to the global and local economy. Diseases and parasitic infections have been recognized as one of the detrimental and limiting factors in the development of aquaculture. No research has been carried out to study the occurrence of parasites in Oreochromis niloticus cultured in pioneer integrated cage fish culture in shallow and temporary water bodies (BOMOSA cages) in Kenya. A study was conducted with the aim of finding out the occurrence of protozoan and helminth parasites in O. niloticus fish from BOMOSA cages and open ponds. The objectives were: to detect and identify parasites, to determine their prevalence, mean intensity, abundance and distribution, and to relate the occurrence of the parasites to seasonality and biotic factors such as presence of intermediate and definitive hosts. Using routine necropsy and parasitological examination procedures a total of 370 O. niloticus fish (57 caged and 313 from open ponds) were examined for the presence of parasites. A total of 3 protozoan and 14 helminths and 1 copepod species were identified. There were no significant differences in parasitic infections between caged and open pond fish (sign test x=8, n=19, p>0.05). In terms of distribution, some parasites seemed more abundant in caged than in open pond fish and vice versa. A few parasites such as the eye fluke Tylodelphys spp. seemed to occur at high intensities during the dry season when the water level in the reservoir was low, while the majority of the parasites did not show any relationship with seasons. The prevalence rate and mean intensities of some helminth parasites identified such as eye fluke, Tylodelphys spp. and Clinostomum spp. warrant for design of control strategies. Even though there were no losses and mortalities recorded during the study period, it should be emphasised that some parasitic infestations can worsen the productive indexes of fish and that some helminth parasites, such as Clinostomatid digeneans, could be pathogenic for man.