Management practices and risk factors associated with parasitic infestations in farmed Nile tilapia in Bomet and Kericho counties, Kenya

Abstract

The aquaculture has surged in Kenya owing to dwindling wild stocks. However, this is coupled with challenges such as limited fish health knowledge and biosecurity measures. A cross sectional study was undertaken to determine risk factors and management practices associated with parasitic infestation of farmed Nile tilapia in Bomet and Kericho counties, Kenya. A total of 150 Nile tilapia (Oreochromis niloticus) were collected and subjected to standard parasitological examination. Potential risk factors associated with parasitic infestation in fish were assessed in 88 farms using pretested semi-structured questionnaires and on-site farm visit observations. Logistic regression analysis with the estimation of odds ratios (OR) was used to assess potential risks factors. Tilapia were dominant fish (>95%) and were farmed mainly in earthen ponds (> 61%). Most farmers (52.3%) used river water for ponds and 14% had experienced floods that introduced predators in the ponds. Farmers relied on fisheries department harvesting nets and only 12.5% sun dried the nets after use. Few farmers (37.5%) frequently cleaned and dried ponds before restocking, while 34.1% did not remove the pond bottom soil after fish harvesting. Approximately 3.4% of the farmers rated diseases as the main obstacle in fish farming and, 68.2% could not identify sick fish. Those who identified sick fish reported abnormal swimming (23.9%) and mortality (8%). Out of the 150 fish sampled, 62 (prevalence = 42%) were found to be infected with different genera of parasites including: Dactylogyrus spp. (21%); Epistylis spp. (7.3%); Riboscyphidia spp. (6.7%); Trichodina spp. (6%); Paracamallanus spp. (4.7%); Camallanus spp. (2%); Diplostomum spp. (2%) and Contracaecum spp. (1.3%). Dactylogyrus spp. were common in earthen ponds (91%) (p<0.001). Some management practices identified as possible risk factors for parasitic infestation in fish included; pond fertilization using livestock manure (OR=5.633), siting fish ponds in valleys/gullies (OR=2.028), use of river water for aqua farming (OR=1.654) and earthen pond types (OR=2.023). Farmers and extension workers should be trained on the importance of fish health and biosecurity. The authors recommend further detailed longitudinal controlled studies which consider myriad fish husbandry practices with parasitic infestations.