Pathogenic landscapes: interactions between land, people, disease vectors, and their animal hosts

Abstract

Background: Landscape attributes influence spatial variations in disease risk or incidence. We present a review of the key findings from eight case studies that we conducted in Europe and West Africa on the impact of land changes on emerging or re-emerging vector-borne diseases and/or zoonoses. The case studies concern West Nile virus transmission in Senegal, tick-borne encephalitis incidence in Latvia, sandfly abundance in the French Pyrenees, Rift Valley Fever in the Ferlo (Senegal), West Nile Fever and the risk of malaria re-emergence in the Camargue, and rodent-borne Puumala hantavirus and Lyme borreliosis in Belgium.

Results: We identified general principles governing landscape epidemiology in these diverse disease systems and geographic regions. We formulated ten propositions that are related to landscape attributes, spatial patterns and habitat connectivity, pathways of pathogen transmission between vectors and hosts, scale issues, land use and ownership, and human behaviour associated with transmission cycles.

Conclusions: A static view of the "pathogenecity" of landscapes overlays maps of the spatial distribution of vectors and their habitats, animal hosts carrying specific pathogens and their habitat, and susceptible human hosts and their land use. A more dynamic view emphasizing the spatial and temporal interactions between these agents at multiple scales is more appropriate. We also highlight the complementarity of the modelling approaches used in our case studies. Integrated analyses at the landscape scale allows a better understanding of interactions between changes in ecosystems and climate, land use and human behaviour, and the ecology of vectors and animal hosts of infectious agents.

Figure 1

Larval index map for the mosquito Anopheles hyrcanus derived from a statistical model associating entomological field data with satellite imagery in the Camargue, France.

Figure 2

Graphical representation of the landscape determinants of disease transmission. The numbers refer to the ten propositions formulated in this paper.

Figure 3

Spread of the mosquito Culex poicilipes around a breeding site in different hypothetical landscapes in the semi-arid region of the Ferlo, Senegal, based on model simulations. Red isolines depict the mosquito density. Vegetation is represented in green and bare soil in yellow.