Emerging Vector-Borne Pathogens at the Wildlife–Human Interface: Ecological Drivers, Surveillance Gaps, and Public Health Implications

Abstract

Vector-borne pathogens occupy a structurally awkward position in global health. They are transmitted by arthropods whose populations are governed by climate, hydrology and land cover; they are maintained in vertebrate reservoirs that belong to no ministry’s mandate; and they reach human beings through contact processes that sit outside the clinical encounter where surveillance systems are designed to detect disease. This review synthesises the evidence on emergence of vector-borne pathogens at the wildlife–human interface, organised around three questions: what ecological processes generate emergence, where surveillance systems fail to see it, and what the resulting public health exposure amounts to. The evidence supports four propositions. First, emergence is driven less by pathogen novelty than by the reorganisation of host and vector communities under land-use change, with zoonotic reservoir hosts systematically over-represented in human-modified landscapes and spillover risk maximised at intermediate levels of land conversion rather than in intact or fully converted habitat. Second, climate change is redistributing rather than simply expanding transmission, with vector range shifts measurable in observed occurrence records and transmission suitability governed by unimodal thermal relationships that can reduce as well as increase risk. Third, transmission in multi-host systems is dominated by heterogeneity: a small number of highly competent and preferentially fed-upon reservoir species carry most amplification, which makes mean host density a poor predictor of risk and makes the biodiversity–disease relationship mechanism-specific rather than general. Fourth, the surveillance architecture that should detect all of this has eroded. Entomological capacity in the United States declined substantially in the decade after West Nile virus became endemic; fewer than half of surveyed national veterinary authorities operate wildlife disease surveillance; and in much of sub-Saharan Africa and Asia, arboviral and bacterial zoonotic febrile illness is presumptively misclassified as malaria and never enters any surveillance stream. The public health implication is that the vector-borne disease