DOES DEFORESTATION DRIVE VISCERAL LEISHMANIASIS TRANSMISSION? A COUNTERFACTUAL ANALYSIS

Objective: The study aimed to estimate the causal relationship between deforestation and the occurence of visceral leishmaniasis (VL) using the São Paulo state (Brazil) as the study case. Methods: We used an innovative two-step counterfactual approach to estimate the effects (overall, direct, and indirect) of deforestation on the occurrence of the VL vector, canine visceral leishmaniasis (CVL), and human visceral leishmaniasis (HVL). We first estimated the parameters via a double Metropolis–Hastings algorithm and then estimated the causal effects through a Gibbs sampler. Results: We observed that the odds of vector, CVL, and HVL occurrence were 2.63-, 2.07-, and 3.18-fold higher, respectively, in deforested compared with forested municipalities. We also identified a significant influence of the presence of vector, CVL, and HVL in one municipality on disease occurrence in previously naive neighbouring municipalities, 6.67, 4.26, and 4.27, respectively. Lastly, we found that a hypothetical reduction in deforestation prevalence from 50% to 0% across the state would reduce vector, CVL, and HVL occurrence by 11%, 6.67%, and 29.87%, respectively. Conclusions: Our results suggest that implementing an eco-friendly development strategy that considers trade-offs between agriculture, urbanisation, and conservation could be an effective mechanism of controlling VL.