Malaria risk among fishermen of Rusinga Island, Western Kenya:an Assessment of different Malaria Transmission Metrics and Human Behaviour

Abstract

Studies were conducted to determine whether capture fishing and associated activities place individuals engaging in them at higher risk of contracting malaria. Consequently, a strategy was developed to create awareness of malaria risk among fisherfolk using a behaviour change monitoring and evaluation approach called Outcome Mapping. The first study sought to assess the burden of malaria and determine indoor and outdoor transmission on Rusinga Island. Anophelesarabiensis was found to be the most abundant malaria vector responsible for both indoor and outdoor transmission. No significant difference in the density of An. arabiensis found indoors and outdoors was observed (p = 0.477). Mosquitoes captured outdoors were found with sporozoites which suggest that individuals conducting fishing activities outdoors at night are at risk of receiving infectious bites. The prevalence of malaria was found to be 10.9% with P. falciparum as the most prevalent parasite. As expected malaria was significantly associated with individuals who did not use protective measures (Odds Ratio = 2.65, 95% Confidence Interval 1.76 – 3.91, p<0.001). Based on these results, the spatial and temporal exposure to malaria mosquitoes in relation to fishing activities was conducted. Two peak mosquito biting times, revealing that fishermen found outdoors at beaches during specific times are at risk of receiving infectious bites, were dentified.Anopheles arabiensis exhibited two biting peaks specifically between 10 - 11pm and 4 – 5am. Two peaks in capture fishing activity, which coincided with the peaks in mosquito biting patterns, were also observed. Of the total persons observed at the beach, 18.8% were counted between 9 – 10pm and 49.7% between 3 – 7am. No significant difference was found in the density of An. Arabiensis at various distances from the shoreline. Compared to mosquitoes captured at close proximity to the shoreline, there was no significant difference in the numbers of An. arabiensis caught at 600 –1200 metres (p = 0.534) and 1200 - 1800 metres (p = 0.742) away. Compared to individuals who live less than 600 metres from the shoreline, other individuals who lived 600 – 1200 metres (p =0.319) and 1200 – 1800 metres (p = 0.312) away were not at a higher risk of malaria as measured by parasite prevalence Another investigation sought to characterize malaria prevalence among outpatients in health facilities and determine the association of the disease to individuals engaged in various livelihoods on the Island. A health facility-based survey revealed that fishermen and farmers were significantly associated with malaria cases. Among patients engaged in different livelihoods, malaria was significantly associated with farmers (p = 0.003), and fishermen (p = 0.031) when compared to adults who were unemployed.Based on these results, a study was carried out to assess risk factors for malaria infection amongfishermen. The study provided knowledge regarding current behaviours exhibited by fishermen that aggravate malaria control. The risk of contracting malaria was three-fold among fishermen who conducted fishing activities in clothes that exposed their arms and legs (95% CI 1.11 – 14.23,p = 0.045) compared to those who dressed in long sleeved clothes. Bednets were not found to be an effective malaria control tool among fishermen since no difference in malaria infection was found among fishermen who used bednets as a personal malaria protection measure or not (OR = 0.38, 95% CI 0.05 – 1.45, p = 0.218).The final study used an outcome mapping approach to measure malaria prevention behaviour change among pre-trained fisherfolk on Rusinga Islnd. A health intervention to create awareness,educate and foster behaviour change was implemented among fisherfolk. The most significant change was observed in attendance of project meetings by project partners. Most of the malaria prevention and control efforts focused on use of treated bed nets and wearing long-sleeved clothing outdoors.In conclusion, the fishermen of Rusinga Island are at risk of contracting malaria because of a temporal convergence between their outdoor activities and peak mosquito biting times. In addition,they are at risk because they do not frequently sleep under treated bednets. Outcome mapping can be used as a tool to demonstrate malaria prevention behaviour change among fisherfolk.