Zoonoses Emergence Linked to Changes in Agriculture & Environment

Expansion of agriculture and associated anthropogenic environmental changes has allowed intensive interactions between humans, livestock, and wildlife. Habitat fragmentation, deforestation, replacement of natural vegetation by crops, encroachments and modification of wildlife population structure and migration have reduced biodiversity by creating environments that favour particular hosts, vectors, and/or pathogens. These have created opportunities for bringing humans and livestock into closer proximity to wildlife and vectors, and the sylvatic cycles of potential zoonotic pathogens.

All drivers allow potential spillover of previously unknown pathogens into livestock or humans along with establishment of new transmission cycles. Jones et al, recently conducted a systematic review to analyse qualitative scientific knowledge in relation to the effect of agricultural intensification and environmental changes on risk of zoonoses at the wildlife–livestock– human interface.

The review found strong evidence that modern farming practices and intensified systems can be linked to disease emergence and amplification. It illustrated several examples of zoonotic disease emergence at the wildlife–livestock–human interface that were associated with varying combinations of agricultural intensification and environmental change.

The authors proposed a conceptual framework of the characteristics of the types of wildlife–livestock–human interface, where zoonotic diseases have emerged or re-emerged. Key features of the systems being their complexity, connectedness, feedback loops, and emerging properties. The review thus highlighted the important fact, that given their diversity and complexity, these systems cannot be captured and understood by single- or multidisciplinary approaches. Simple, globally generalised explanations for zoonoses emergence are not possible.

Local interdisciplinary studies need to be conducted to generate locally relevant solutions. A priority for research, therefore should be a holistic perspective on pathogen dynamics at the wildlife–livestock–human interface, based on an interdisciplinary approach to the examination of biological, ecological, economic, and social drivers of pathogen emergence.

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