Habitat fragmentation and the transmission and emergence of pathogens across habitat boundaries
The fragmentation of intact wildlife habitat and conversion to human-dominated landscapes is occurring globally. As fragmentation occurs, wildlife hosts are found primarily in habitat patches that resemble their original habitat but also can be found in human- and livestock- dominated ‘matrix’ surrounding these patches. Changes in the size and distribution of optimal habitat influences wildlife populations, but also their pathogens. Several studies suggest that increasing contact between wildlife and humans as habitat fragmentation occurs leads to zoonotic disease emergence, however there is not a conceptual framework in investigating factors that influence the risk of spillover into the matrix, mainly in human and domestic animals. We present a stochastic model that incorporates: 1) patch size, shape, perimeter, 2) edge effects, 3) host movement between patch and matrix, and 4) species interactions within and between animals in matrix and the patch to predict novel spillover risk.
Applying our modeling framework to Plasmodium knowlesi-macaque-human- mosquito system reveals that edge:habitat and relative infection probabilities are most important to quantify when evaluating disease spillover between forest fragments and matrix habitats. Our modeling framework can improve our understanding of how diseases emerge and persist between forest patches and surrounding deforested matrix in the context of deforestation and forest fragmentation.