Prevalence, Intensity and Risk Factors Associated With Parasitic Infestations of Farmed and Wild Oreochromis Species in Selected Counties in Kenya

Abstract

Fish parasites are catastrophic in aquaculture as they cause mass mortality, morbidity and rejections of fish in the market due to loss of aesthetic value. Therefore, to boost aquaculture production in Kenya, proper biosecurity measures and farm management practices should be in place and understood by farmers. The objective of study was to determine the prevalence, intensity and risk factors associated with parasitic infestations of farmed and wild Oreochromis species in selected counties in Kenya. The study was conducted between March and July 2023 in fish farms from the following counties, Kericho, Bomet, Nakuru and Taita Taveta and Lake Jipe in Taveta Sub-county. A total of 88 questionnaires were administered to fish farmers in Kericho and Bomet counties to assess the fish farming and management practices that could influence occurrence of parasites in farmed fish. A total of 331 tilapias were examined for parasites following standard parasitological procedures. The pH, temperature and dissolved oxygen were measured using a mobile waterproof HANNA Multiprobe meter before 10.00am and two litres of water from the pond were taken to the Government Chemist for spectrophotometric analysis. Fish were mainly farmed in earthen ponds with most ponds located in valleys and depended on river water. Tilapia was the dominant species and was mainly sourced from Government hatcheries, and. 47% of the farmers had mixed sex tilapias breeding prolifically in their farms. Ninety-one percent of farmers drained their pond, 33% did not clean and dry ponds before restocking while 34% removed pond bottom sediments after harvesting their fish. There were few cases of diseases, however most of the farmers had little knowledge on fish health. Management practices associated with fish parasite infestation were use of livestock manure (OR=5.633), pond location (OR=2.028), water source (OR=1.654) and pond type (OR=2.023). Of the 331 fish examined, 43.8% were infested with one or more of parasites from eleven genera

recovered. Dactylogyrus, Acanthocephalus and Diplostomum species occurrence was mainly influenced by culture systems. Diplostomum sp. had negative impact on body condition factor of infested fish (< 0.003). Oreochromis jipe had the highest prevalence of parasitic infestations compared to other Oreochromis species in Taita Taveta County (p>0.05). Riboscyphidia sp. had highest mean intensity of 32.40±42.74 in Kericho County and 27.0±48.7 in earthen ponds. Diplostomum sp. intensity was high in Kericho (4.67±4.73) and in liner ponds (3.78±3.42). Acanthocephalus sp. intensity was high in Taita Taveta County (3.65±2.57) and in liner (3.86±2.63) ponds (p>0.05). Ammonia, sulphate, nitrates, pH, phosphorus, dissolved oxygen, turbidity, suspended solid particles and electrical conductivity concentration in water had positive correlation with different parasites. This study has found that some management practices, water quality parameters and holding systems influenced the occurrence of fish parasites. Therefore, it is crucial for farmers to monitor water quality parameters to mitigate parasitic infestations. The study recommends molecular characterization of fish parasites recovered in the four study counties and elsewhere in Kenya