Parasitic Infections of Freshwater Fish in Kenya: Prevalence Patterns, Ecological Drivers, and Implications for Aquaculture Sustainability

Abstract

Fish parasitic infections present a growing threat to freshwater aquaculture in Kenya, affecting fish health, reducing productivity, and limiting the economic potential of small-scale and commercial farms. This review provides the first consolidated national checklist of freshwater fish parasites in Kenya, synthesizing evidence from lakes, rivers, and aquaculture systems across multiple counties. By integrating data from diverse host species and production environments, it establishes a comprehensive baseline on parasite diversity, host range, and geographic distribution that has previously been fragmented across isolated studies. Studies were identified through a structured search of scientific databases. The review highlights the widespread occurrence of parasitic infections in economically important species, such as Oreochromis, Clarias, Lates, Haplochromis, Barbus, and Cyprinus. Parasites identified included ectoparasites, a haemoparasite, helminths, and an acanthocephalan. Helminths, especially digenean trematodes, were the most commonly reported. Infection prevalence varied across production systems, with higher diversity and burden in earthen ponds and natural lakes compared with lined or concrete ponds. The most frequently encountered genera were Gyrodactylus, Diplostomum, Contracaecum, and Proteocephalus, affecting both wild and cultured fish populations. Risk factors influencing parasite prevalence were linked to environmental conditions and farm management practices. Poor water quality, overstocking, reuse of contaminated nets, retention of pond bottom sediments after harvest, and use of untreated livestock manure were frequently associated with increased infections. Ecological factors such as the presence of wild birds and aquatic snails were also implicated in sustaining transmission cycles. Seasonal flooding further contributed to parasite dispersal in some regions. The review underscores the need for integrated parasite management strategies. This includes routine monitoring using advanced diagnostics, improved biosecurity practices at farm level, targeted training of farmers and extension workers, and reduced dependence on high-risk inputs such as raw manure. Public awareness on zoonotic risks of fish-borne parasites should also be strengthened. Investing in research to explore vaccine development and the role of environmental drivers in parasite ecology will be essential in safeguarding the sustainability of Kenya's freshwater aquaculture sector.