Amphibian Collapses Exacerbated Malaria Outbreaks in Central America

Abstract

AbstractEcosystems play an important role in supporting human welfare, including regulating the transmission of infectious diseases. Many of these services are not fully-appreciated due to complex environmental dynamics and lack of baseline data. Multicontinental amphibian decline due to the fungal pathogen Batrachochytrium dendrobatidis (Bd) provides a stark example. Even though amphibians are known to affect natural food webs—including mosquitoes that transmit human diseases—the human health impacts connected to their massive decline have received little attention. Here we show a causal link between a wave of Bd-driven collapse of amphibians in Central America and increased human malaria incidence. At the canton-level in Costa Rica and district-level in Panama, expected malaria incidence increased for eight years subsequent to amphibian losses, peaking at an additional 1.0 cases per 1,000 population (CPK). The increase is substantial in comparison to annual incidence levels from outbreaks in these countries, which peaked at 1.1-1.5 CPK during our period of study from 1976-2016. This pattern holds across multiple alternative approaches to the estimation model. This previously unidentified impact of biodiversity loss illustrates the often hidden human welfare costs of conservation failures. These findings also show the importance of mitigating international trade-driven spread of similar emergent pathogens like Batrachochytrium salamandrivorans.Significance StatementDespite substantial multicontinental collapses in amphibian populations from spread of the fungal pathogen Batrachochytrium dendrobatidis (Bd), the implications for humans have not been systematically studied. Amphibians are known to affect food webs, including mosquitoes that serve as a vector for the spread of disease. However, little is known about how their loss erodes ecosystem services, including the regulation of the transmission of infectious diseases. Using Central America as a case study, this study shows that Bd-driven amphibian loss led to a substantial increase in malaria incidence. The results highlight the often underappreciated social costs of biodiversity loss, including the potential stakes of ecosystem disruption from failing to stop spread of future novel pathogens.