Introduction

The social changes occurring across Europe in the last 40 years have had a pronounced effect on the environment, creating a dynamic situation where new pathogens or new hosts emerge, changes in population density or host behaviour affect disease prevalence and, in some cases, may allow disease agents to boost their virulence and widen their host range (Figure 7.1).

Apart from the role of pathogens in the population dynamics of wild populations of ungulates (discussed here in Chapter 11), another significant issue is the risk of transmission of disease agents between wildlife and livestock or human beings. While some pathogens exclusively infect a single host species, these are usually highly coevolved parasites with limited effect on the primary host's population (Crawley, 1992; Vicente et al., 2004a). In contrast, many parasites can infect multiple host species and these are primarily responsible for outbreaks of infectious diseases in humans, livestock and indeed among wildlife (Swinton et al., 2002; Woolhouse, 2002).

The increased distribution and densities of wild ungulates registered all across Europe (see chapters in Apollonio et al., 2010), together with a move within the livestock industry from more intensive to more extensive farming systems, or at least systems with a lower human presence on the field, have increased the risk of contact between wildlife and livestock (e.g. Laddomada et al., 1994; Gortázar et al., 2007).