Spatio-temporal associations between deforestation and malaria incidence in Lao PDR

Abstract

As countries in the Greater Mekong Sub-region (GMS) increasingly focus their malaria control and elimination efforts on reducing forest-related transmission, greater understanding of the relationship between deforestation and malaria incidence will be essential for programs to assess and meet their 2030 elimination goals. Leveraging village-level health facility surveillance data and forest cover data in a spatio-temporal modeling framework, we found evidence that deforestation is associated with short-term increases, but long-term decreases in confirmed malaria case incidence in Lao People's Democratic Republic (Lao PDR). We identified strong associations with deforestation measured within 30 km of villages but not with deforestation in the near (10 km) and immediate (1 km) vicinity. Results appear driven by deforestation in densely forested areas and were more pronounced for infections with Plasmodium falciparum (P. falciparum) than for Plasmodium vivax (P. vivax). These findings highlight the influence of forest activities on malaria transmission in the GMS.

Characterizing the spatial distribution of multiple malaria diagnostic endpoints in a low-transmission setting in Lao PDR

“…The districts were chosen to focus on areas of malaria hotspots, and to ensure representation by surveying from diverse epidemiological settings ( 1 ). At the time of the study P. vivax was endemic and P. falciparum had reached historical lows in these provinces ( 3 ). It is a mountainous region characterized by a diverse climate, with low population density and limited access to roads ( 1 , 3 ).…”

“…At the time of the study P. vivax was endemic and P. falciparum had reached historical lows in these provinces ( 3 ). It is a mountainous region characterized by a diverse climate, with low population density and limited access to roads ( 1 , 3 ). The region shares borders with China, Myanmar, Thailand and Vietnam.…”

“…Through an intensification of their programmatic activities and an increased coverage of interventions ( 1 ), the Lao People's Democratic Republic (PDR) has seen substantial declines in malaria cases, with a fall in case incidence by 80% from 2016 to 2020, and no reported malaria deaths since 2018 ( 2 ). Transmission is very low in northern Lao PDR, with P. vivax cases making up the majority of malaria burden ( 1 , 3 ). The nation aims to eliminate Plasmodium vivax and Plasmodium falciparum from northern areas by 2025, and all species nationwide by 2030 ( 2 , 4 ).…”

“…We ran blood samples from a 2016 active surveillance population survey ( 1 ) in northern Lao PDR using a serology MBA to gain an understanding of current and historic exposures to P. vivax and P. falciparum . We additionally used passive surveillance (case incidence) data collected from health facilities in the same districts ( 3 ) to compare serology and PCR-derived prevalences with burden estimates from active surveillance at the health facility catchment- level. We fit geostatistical models to predict historic and recent exposures to P. vivax and P. falciparum .…”

Uncertainty of Historic GLAD Forest Data in Temperate Climates and Implications for Forest Change Modelling

“…Although the GLAD forest cover products are primarily intended to serve as a near real-time flag for areas of forest loss, it is increasingly also being used in ways that go beyond this initial focus. Examples are the assessment of above-ground biomass across tropical forests [17] and the link between deforestation and malaria incidence [18]. Shah et al (2018) used Global Forest Cover data to estimate potential locations for the origins of next forest-based emerging infectious disease [19].…”