Abstract
ABSTRACT.As countries of sub-Saharan Africa expand irrigation to improve food security and foster economic growth, it is important to quantify the malaria risk associated with this process. Irrigated ecosystems can be associated with increased malaria risk, but this relationship is not fully understood. We studied this relationship at the Bwanje Valley Irrigation Scheme (800 hectares) in Malawi. Household prevalence of malaria and indoor Anopheles density were quantified in two cross-sectional studies in 2016 and 2017 (5,829 residents of 1,091 households). Multilevel logistic regression was used to estimate the association between distance to the irrigation scheme and malaria infection and mosquito density. The prevalence of malaria infection was 50.2% (2,765/5,511) by histidine-rich protein 2–based malaria rapid diagnostic tests and 30.1% (1,626/5,403) by microscopy. Individuals residing in households within 3 km of the scheme had significantly higher prevalence of infection (adjusted odds ratio [aOR] = 1.41; 95% confidence interval [CI] 1.18, 1.68); school-aged children had the highest prevalence among age groups (aOR = 1.34; 95% CI 1.11, 1.63). Individuals who reported bed net use, and households with higher socioeconomic status and higher level of education for household head or spouse, had lower odds of malaria infection. Female Anopheles mosquitoes (2,215 total; Anopheles arabiensis, 90.5%, Anopheles funestus, 9.5%) were significantly more abundant in houses located within 1.5 km of the scheme. Proximity of human dwellings to the irrigation scheme increased malaria risk, but higher household wealth index reduced risk. Therefore, multisectoral approaches that spur economic growth while mitigating increased malaria transmission are needed for people living close to irrigated sites.
Highlights
Malaria remains a significant global health problem with an estimated 229 million cases and 409,000 deaths in 2019 alone.[1]
Intensive use of malaria control measures has resulted in substantial reduction in disease burden: district-level prevalence for infection with Plasmodium falciparum declined by 47.2% from 29.4% in 2010 to 15.2% in 2017.2 the country remains a highburden country with meso-endemic malaria transmission risk.[2]
Some studies have shown higher malaria prevalence for those living in households in close proximity to traditional flooded rice schemes,[14,16,31] our findings demonstrate that the Bwanje Valley Irrigation Scheme (BVIS) scheme added to the burden of malaria with an obvious distance decay: malaria infection prevalence declined with distance of human dwellings to the scheme
Summary
Malaria remains a significant global health problem with an estimated 229 million cases and 409,000 deaths in 2019 alone.[1] The risk of the disease remains high in many subSaharan African (SSA) countries, including Malawi. In 2019, Malawi’s estimated annual country-wide incidence of malaria was 207 per 1,000 individuals including 6,308 deaths.[1] In the past decade, intensive use of malaria control measures has resulted in substantial reduction in disease burden: district-level prevalence for infection with Plasmodium falciparum declined by 47.2% from 29.4% in 2010 to 15.2% in 2017.2 the country remains a highburden country with meso-endemic malaria transmission risk.[2]. Variation in the spatiotemporal patterns of malaria risk and disease burden depend on, among other factors, the environment, vector ecology, and the coverage and use of control measures. Agroecological environments have generally been associated with increased malaria intensity.[3,4,5,6,7,8] Studies have shown that the characteristics of the farming practices, crop types, proximity of households to breeding habitats, and coverage and uptake of malaria control measures affect
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