Does deforestation promote or inhibit malaria transmission in the Amazon? A systematic literature review and critical appraisal of current evidence

Abstract

Considerable interest in the relationship between biodiversity and disease has recently captured the attention of the research community, with important public policy implications. In particular, malaria in the Amazon region is often cited as an example of how forest conservation can improve public health outcomes. However, despite a growing body of literature and an increased understanding of the relationship between malaria and land use / land cover change (LULC) in Amazonia, contradictions have emerged. While some studies report that deforestation increases malaria risk, others claim the opposite. Assessing malaria risk requires examination of dynamic processes among three main components: (i) the environment (i.e. LULC and landscape transformations), (ii) vector biology (e.g. mosquito species distributions, vector activity and life cycle, plasmodium infection rates), and (iii) human populations (e.g. forest-related activity, host susceptibility, movement patterns). In this paper, we conduct a systematic literature review on malaria risk and deforestation in the Amazon focusing on these three components. We explore key features that are likely to generate these contrasting results using the reviewed articles and our own data from Brazil and Peru, and conclude with suggestions for productive avenues in future research.This article is part of the themed issue ‘Conservation, biodiversity and infectious disease: scientific evidence and policy implications'.

Conservation, biodiversity and infectious disease: scientific evidence and policy implications

“…Tucker Lima et al [26] reconcile the conflicting accounts about how malaria responds to changing land use in the Amazon. Through a systematic literature review, the authors illustrate the complex pathways connecting land use to malaria burden.…”

Impact of deforestation on the abundance, diversity, and richness of Culex mosquitoes in a southwest Cameroon tropical rainforest

“…All these observations confirm that Culex species could easily adapt to environmental degradation following complete deforestation. However, each mosquito species has unique life‐history characteristics and habitat preferences, and therefore reacts differently to landscape changes (Tucker et al ).…”

“…Global climate change and increasing human population growth, together with human‐induced modifications of terrestrial ecosystems, have been implicated as major factors contributing to the emergence of new and previously known infectious diseases (Leisnham and Juliano , Kweka et al , Tucker et al ). Among the most obvious habitat losses is the large‐scale tropical deforestation (Lewis et al ) that is likely responsible for global climate changes (Bala et al , Shukla et al ).…”

“…In the southeastern part of Cote d'Ivoire, where large parts of rainforest have been converted into oil palm plantations, several outbreaks of yellow fever and dengue have been documented (Komono ), and around 60 examples of linkage between deforestation and land‐use changes, and increases in mosquito populations and malaria risk were noted by Yasuoka and Levins (). It should be pointed out, though, that the effects that deforestation has had on human malaria is complex, where the changes from low to high, high to low, and no change in prevalence is very region specific (Austin et al , Bamou et al , Tucker et al ). Another example of the devastating effects of habitat disturbances was in Hawaii, where virulent Plasmodium relictum infected native Hawaiian birds and led to their deaths and extinction.…”

Forêts tropicales, changements d’usage des sols et risques infectieux émergents

“…C'est notamment le cas avec le paludisme pour lequel les effets causés par la déforestation dépendent notamment de l'adaptabilité des vecteurs principaux à ces modifications d'habitat. Cette maladie parasitaire a ainsi tendance à reculer dans les zones de déforestation en Asie du Sud-Est, alors qu'elle y progresse en Afrique ou en Amérique du Sud [27,80,81]. Le lien entre biodiversité et risque d'émergence est ainsi âprement débattu au sein de la communauté scientifique, certains auteurs mettant en avant un lien fort et universel entre perte de biodiversité et nouvelles émergences infectieuses, arguant que cette perte de biodiversité intervient principalement dans des zones de déforestation de forêts tropicales primaires [82], d'autres auteurs mettant en avant le caractère contextuel de ce lien, qui peut varier en fonction des espèces animales et des agents pathogènes considérés [83] voire géographiquement au sein d'un même système infectieux [45].…”