Shaping zoonosis risk: landscape ecology vs. landscape attractiveness for people, the case of tick-borne encephalitis in Sweden

Abstract

BackgroundIn this paper, the hazard and exposure concepts from risk assessment are applied in an innovative approach to understand zoonotic disease risk. Hazard is here related to the landscape ecology determining where the hosts, vectors and pathogens are and, exposure is defined as the attractiveness and accessibility to hazardous areas. Tick-borne encephalitis in Sweden was used as a case study.MethodsThree boosted regression tree models are compared: a hazard model, an exposure model and a global model which combines the two approaches.ResultsThe global model offers the best predictive power and the most accurate modelling. The highest probabilities were found in easy-to-reach places with high landscape diversity, holiday houses, waterbodies and, well-connected forests of oak, birch or pine, with open-area in their ecotones, a complex shape, numerous clear-cuts and, a variation in tree height.ConclusionWhile conditions for access and use of hazardous areas are quite specific to Scandinavia, this study offers promising perspectives to improve our understanding of the distribution of zoonotic and vector-borne diseases in diverse contexts.

Scouts, forests, and ticks: Impact of landscapes on human-tick contacts

“…As in Zeimes et al (2014), explanatory variables were allocated to hazard or exposure, but some were included in both classes ( Table 1). …”

“…Linard et al (2007) also pointed out the significance of adding variables related to human behaviour and land use in addition to land cover and habitat variables in epidemiological models. Moreover, Zeimes et al (2014) showed that a model considering hazard and exposure offers better predictive power than models considering only hazard or exposure.…”

“…The risk of TBD results from the combination of both hazard and exposure (Zeimes et al, 2014). Hazard represents the strength of the zoonotic transmission cycle, and is determined by biotic and abiotic factors that affect vectors and hosts.…”

“…Exposure represents the intensity of contact that people have, in relation to their activities and preferences, with places where infected ticks are present. It is determined, in the case of recreational uses of wooded areas, by landscape attractiveness and accessibility (Zeimes et al, 2014). Although disease ecology studies have extensively studied hazard (Estrada-Peña, 2001;Lindström and Jaenson, 2003;Rizzoli et al, 2009;Li et al, 2012), they often overlook factors determining human exposure, which are more studied by epidemiologists (Méha, 2012).…”

Individual and environmental factors associated with the seroprevalence ofBorrelia burgdorferiin Belgian farmers and veterinarians

“…The landscape also affects the spatial distribution of human activities and thus contacts between susceptible humans and infected ticks (9). Complex and fragmented landscapes provide more ecotones (transition area between two adjacent biomes) and can increase contacts between species associated with diverse habitats, including reservoir hosts and ticks, and increase accessibility to forests (10, 11). Furthermore, landscape fragmentation can influence biodiversity (12).…”