ENTOMOLOGICAL AND PARASITOLOGICAL INDICES OF MALARIA TRANSMISSION AMONG RESIDENTS OF GOLD MINING AND SUGARCANE FARMING AREAS IN WESTERN KENYA

Abstract

malaria and its subsequent eradication, the disease remains a major public health concern. Of the deaths due to the malaria scourge, Sub-Saharan Africa accounted for 92% with children under 5 years old accounting for 61% deaths. In Kenya, malaria accounts for 3.5 million clinical cases which resulted in 10,700 deaths annually. In as much as there was a marked decrease in malaria cases, due to up-scaling of the available control interventions, the intended goals aimed at malaria control and eventual elimination in endemic countries have not been very successful. Malaria epidemics in highlands have been associated with many factors which included climate change, drug resistance, and activities that modify land among others. The implication of malaria to land transforming activities such as artisanal gold mining, sugarcane farming, and the distance of residential houses from the mosquito breeding sites, made it possible that gold mining in Rosterman and sugarcane farming in Eluche played a significant role in the observed increased malaria incidences in Western Kenya. However, there was a lack of cogent evidence-based documentation about this scenario. Therefore, this study determined entomological and parasitological indices of malaria transmission among residents of gold mining and sugarcane growing regions in Western Kenya. This study involved both quantitative and qualitative data collection. A Survey of the mosquito breeding sites for the immature forms and collection of the adult mosquitoes by pyrethrum spray catches and light traps was done 3 consecutive days every month for 12 months starting November 2018. Blood samples by finger prick were collected on microscope slides and filter papers for parasitological studies from August 2020 to May 2021. Species identification was done for Anopheles and Plasmodium spp. Anopheles was identified by use of morphological keys and by molecular means, while Plasmodium spp were identified and quantified microscopically and molecular by use of polymerase chain reaction. Mixed method study design involving questionnaires, interviews, and focused group discussions was used to collect data from the residents. GraphPad Prism statistical package was used in data analyses. Descriptive statistics were carried out to determine relative frequencies and proportions. F-test tested the productivity of the larval habitats and the association between the month of sampling and adult Anopheles abundance, while the t-test tested the association between mean malaria prevalence and the site, season and age bracket at 95% confidence interval and p ≤ 0.05 was considered statistically significant. Mosquito breeding habitats due to human activities were the most prevalent (93.22%) and had the highest productivity of the developmental stages of Anopheles, in which Gold Mines were the most abundant (51.29%). The average distance of the aquatic habitats from the nearest house was 251 ± 50 m. An. gambiae s.l. (91.96%) was the most abundant vector, while P. falciparum (99%) was the most prevalent malaria parasite. Plasmodium spp prevalence were at 8.96% by rapid diagnostic tests and 9.25% by both microscopy and polymerase chain reaction of dried blood samples. Plasmodium spp parasite mean densities at 95% CI was 4,840 (250 – 18,000) parasites/μl of blood. This study findings have elucidated that An. gambiae is the main vector of malaria and P. falciparum was the most prevalent malarial parasite in Rosterman mines and Eluche sugarcane farming areas in Western Kenya. It was suggested that research should be done to determine if there could be resistant markers in Plasmodium isolates from the people in the study sites and human blood index of the local malaria vectors to directly link them to malaria transmission.