Wildlife disease prevalence in human‐modified landscapes

Abstract

Human-induced landscape change associated with habitat loss and fragmentation places wildlife populations at risk. One issue in these landscapes is a change in the prevalence of disease which may result in increased mortality and reduced fecundity. Our understanding of the influence of habitat loss and fragmentation on the prevalence of wildlife diseases is still in its infancy. What is evident is that changes in disease prevalence as a result of human-induced landscape modification are highly variable. The importance of infectious diseases for the conservation of wildlife will increase as the amount and quality of suitable habitat decreases due to human land-use pressures. We review the experimental and observational literature of the influence of human-induced landscape change on wildlife disease prevalence, and discuss disease transmission types and host responses as mechanisms that are likely to determine the extent of change in disease prevalence. It is likely that transmission dynamics will be the key process in determining a pathogen's impact on a host population, while the host response may ultimately determine the extent of disease prevalence. Finally, we conceptualize mechanisms and identify future research directions to increase our understanding of the relationship between human-modified landscapes and wildlife disease prevalence. This review highlights that there are rarely consistent relationships between wildlife diseases and human-modified landscapes. In addition, variation is evident between transmission types and landscape types, with the greatest positive influence on disease prevalence being in urban landscapes and directly transmitted disease systems. While we have a limited understanding of the potential influence of habitat loss and fragmentation on wildlife disease, there are a number of important areas to address in future research, particularly to account for the variability in increased and decreased disease prevalence. Previous studies have been based on a one-dimensional comparison between unmodified and modified sites. What is lacking are spatially and temporally explicit quantitative approaches which are required to enable an understanding of the range of key causal mechanisms and the reasons for variability. This is particularly important for replicated studies across different host-pathogen systems. Furthermore, there are few studies that have attempted to separate the independent effects of habitat loss and fragmentation on wildlife disease, which are the major determinants of wildlife population dynamics in human-modified landscapes. There is an urgent need to understand better the potential causal links between the processes of human-induced landscape change and the associated influences of habitat fragmentation, matrix hostility and loss of connectivity on an animal's physiological stress, immune response and disease susceptibility. This review identified no study that had assessed the influence of human-induced landscape change on the prevalence of a wildlife sexually transmi...

The relationship between physiological stress and wildlife disease: consequences for health and conservation

“…(2) Habitat disturbance Brearley et al (2013) reviewed the profound impact that habitat loss and fragmentation can have on the prevalence of wildlife disease, and highlighted the role that stress was likely to play as a mediator of this impact. Recent studies have examined the physiological stress response of wildlife to habitat loss and fragmentation (Davies et al 2013).…”

“…Stress has also been suggested as a factor influencing a wide range of diseases in wildlife, including Chlamydia infection in koalas (Brearley et al 2013), toxoplasmosis in various marsupials (Thompson et al 2010), chytridimycosis in amphibians (Blaustein et al 2012;Kindermann et al 2012;Gabor et al 2013), avian influenza in migratory birds (Weber and Stilianakis 2007) and white nose syndrome (Cryan et al 2010) and zoonotic (spread from animals to humans) viruses in bats, including Ebola and Hendra virus (HeV) (Groseth et al 2007;Plowright et al 2014). However, associations between stress and disease in wildlife are not commonly empirically tested.…”

Abandonment, Ecological Assembly and Public Health Risks in Counter-Urbanizing Cities

“…There is an assortment of conditions in cities that can interrupt host-pathogen dynamics and increase risk of zoonotic disease transmission [95]. Urbanized areas tend to elevate the threat of EIDs due to proximate socioenvironmental drivers of disease emergence including: Increased human movement and population density, air pollution, drinking water and sanitation system insecurity, limited access to health care services, as well as rapid land use and socioeconomic change [94][95][96].…”

Ecology and movement of urban koalas adjacent to linear infrastructure in coastal south-east Queensland

“…Recently, an important role has been suggested for disease in the decline of koala populations, with chlamydial infection being implicated as the primary cause of disease (Timms 2005;Markey et al 2007;Higgins 2008). Exacerbation of the disease may be attributed to the koala retrovirus (Tarlinton et al 2005) and stress from habitat clearing and other anthropogenic impacts (Weigler et al 1988;Lee et al 2010;Brearley et al 2013). In addition to these threats, urban koalas face increased mortality from dog attacks and vehicle collisions (Smith and Smith 1990;Melzer et al 2000;Stratford et al 2000;Dique et al 2003b;McAlpine et al 2006).…”

“…These behavioural responses can trigger negative physiological changes in an animal, especially when habitat alterations lead to increased predation, competition for resources and mates, and habitat fragmentation (Brearley et al 2013;Dowle et al 2012), which in turn can lead to changes in movements (Strevens 2007;Asari et al 2010). Yet koalas still persist in disturbed urban landscapes where there are resources they can use.…”