Artisanal fishing supports breeding of malaria mosquitoes in Western Kenya

Abstract

Background: Everyday hundreds of people, mainly men, set out to take part in a vibrant artisanal capture fishing (ACF) industry on Lake Victoria. It is not known whether actions of artisanal fishers, in their unrelenting quest for existence, surpass ecosystems' sustainability thresholds with potentially negative repercussions on human health with respect to malaria transmission potential. This article sought to fill this information gap.

Methods: This study used an ecosystem approach to find out how ACF processes facilitate the breeding of mosquitoes. The observational study adopted a cross-sectional design and was carried out on Mageta Island situated inside Lake Victoria in western Kenya.

Results: Of the 87 mosquito larval habitats identified 27 (31%) were created through ACF activities. The ACF-related habitats, hereafter collectively referred to as 'fishing habitats', included fishing boats (24), trenches (1) and fish bait mines (2). About half (48%) of Anopheles larvae were recovered from fishing habitats. The mean larval density in the fishing habitats (35.7 ± 1.15) was double that in non-fishing habitats (17.4 ± 0.539). Despite being the most common 'non-fishing habitat' type (N = 32), the mean number of Anopheles larvae present in rock pools (30.81 ± 10.54) was significantly less than those found inside fishing boats (N = 24; 40.08 ± 10.16). Overall, man-made habitats and those used to support livelihoods contained significantly more Anopheles larvae.

Conclusions: These data show that artisanal capture fishing is a key driver of malaria epidemiology on Mageta Island. This suggests that larval source management strategies in the global south should pay attention to the heterogeneity in Anopheles breeding habitats created through livelihood activities.

Keywords: Anopheles gambiae; Artisanal capture fishing; Ecohealth; Ecosystem health; Fishing boats; Habitat; Kenya; Lake Victoria; Larval productivity; Mageta Island; Malaria; Mosquito larvae.

Fig. 1

Study area map showing location of Mageta Island in Western Kenya

Fig. 2

Mosquito larval habitat types found on Mageta Island in Lake Victoria, Western Kenya. Areas with stagnant water are circled in red

Fig. 3

Spot map showing geographical location of Anopheles larval habitats on Mageta Island in western Kenya. The center of the rings is the exact location of the habitats

Fig. 4

Modelled probabilities of finding Anopheles mosquitoes in larval habitats associated with (artisanal capture) fishing

Fig. 5

Mean number of Anopheles larvae collected from different mosquito habitat types (a) on Mageta Island in western Kenya. Mean numbers of larvae collected from ‘fishing’ versus ‘non-fishing’ habitats (b) and from habitats with different surface bottom types (c) plus the standard errors of the mean values are shown. Bars with different letters (within the same panel) denote a significant difference in the mean number of mosquitoes collected. Similar letters (within the same panel) indicate no difference in the mean number of mosquitoes collected. No Anopheles larvae were recovered from fishing ponds, fish bait mines and trenches