How will climate change pathways and mitigation options alter incidence of vector-borne diseases? A framework for leishmaniasis in South and Meso-America

The enormous global burden of vector-borne diseases disproportionately affects poor people in tropical, developing countries. Changes in vector-borne disease impacts are often linked to human modification of ecosystems as well as climate change. For tropical ecosystems, the health impacts of future environmental and developmental policy depend on how vector-borne disease risks trade off against other ecosystem services across heterogeneous landscapes. By linking future socio-economic and climate change pathways to dynamic land use models, this study is amongst the first to analyse and project impacts of both land use and climate change on continental-scale patterns in vector-borne diseases. Models were developed for cutaneous and visceral leishmaniasis in the Americas—ecologically complex sand fly borne infections linked to tropical forests and diverse wild and domestic mammal hosts. Both diseases were hypothesised to increase with available interface habitat between forest and agricultural or domestic habitats and with mammal biodiversity. However, landscape edge metrics were not important as predictors of leishmaniasis. Models including mammal richness were similar in accuracy and predicted disease extent to models containing only climate and land use predictors. Overall, climatic factors explained 80% and land use factors only 20% of the variance in past disease patterns. Both diseases, but especially cutaneous leishmaniasis, were associated with low seasonality in temperature and precipitation. Since such seasonality increases under future climate change, particularly under strong climate forcing, both diseases were predicted to contract in geographical extent to 2050, with cutaneous leishmaniasis contracting by between 35% and 50%. Whilst visceral leishmaniasis contracted slightly more under strong than weak management for carbon, biodiversity and ecosystem services, future cutaneous leishmaniasis extent was relatively insensitive to future alternative socio-economic pathways. Models parameterised at narrower geographical scales may be more sensitive to land use pattern and project more substantial changes in disease extent under future alternative socio-economic pathways.

虫媒传染病（vector-borne diseases）带来的全球沉重疾病负担，对热带发展中国家的贫困人群造成了不成比例的影响。虫媒传染病影响的变化往往与人类对生态系统的改造以及气候变化息息相关。对于热带生态系统而言，未来环境与发展政策带来的健康影响，取决于在异质性景观（heterogeneous landscapes）中，虫媒传染病风险与其他生态系统服务（ecosystem services）之间的权衡关系。本研究将未来社会经济与气候变化路径与动态土地利用模型相结合，是首批分析并预测土地利用与气候变化对大陆尺度虫媒传染病分布格局影响的研究之一。研究针对美洲的皮肤利什曼病（cutaneous leishmaniasis）与内脏利什曼病（visceral leishmaniasis）开发了模型——这两种均为经由生态复杂的白蛉（sand fly）传播的感染性疾病，与热带森林以及多样的野生与家养哺乳动物宿主相关。研究假设，随着森林与农业或人居栖息地之间的界面生境增加，以及哺乳动物生物多样性提升，这两种疾病的传播都会加剧。然而，景观边缘度指标并未成为利什曼病的重要预测因子。纳入哺乳动物丰富度的模型，其预测准确性与仅包含气候与土地利用预测因子的模型相近，且二者对疾病波及范围的预测结果相似。总体而言，气候因素解释了过去疾病格局中80%的变异，而土地利用因素仅解释了20%。两种疾病（尤其是皮肤利什曼病）均与较低的气温与降水季节变化性相关。由于未来气候变化下（尤其是在强气候强迫情景下）这类季节变化性会增强，因此预计到2050年，两种疾病的地理分布范围都会缩减，其中皮肤利什曼病的缩减幅度将达到35%至50%。尽管在针对碳、生物多样性与生态系统服务的强管理情景下，内脏利什曼病的缩减幅度略高于弱管理情景，但未来皮肤利什曼病的波及范围对不同的未来社会经济路径（socio-economic pathways）相对不敏感。在更精细的地理尺度上进行参数化的模型，可能对土地利用格局更为敏感，且在未来不同社会经济路径下，预测的疾病波及范围变化会更为显著。