Non-random biodiversity loss underlies predictable increases in viral disease prevalence

Abstract

Disease dilution (reduced disease prevalence with increasing biodiversity) has been described for many different pathogens. Although the mechanisms causing this phenomenon remain unclear, the disassembly of communities to predictable subsets of species, which can be caused by changing climate, land use or invasive species, underlies one important hypothesis. In this case, infection prevalence could reflect the competence of the remaining hosts. To test this hypothesis, we measured local host species abundance and prevalence of four generalist aphid-vectored pathogens (barley and cereal yellow dwarf viruses) in a ubiquitous annual grass host at 10 sites spanning 2000 km along the North American West Coast. In laboratory and field trials, we measured viral infection as well as aphid fecundity and feeding preference on several host species. Virus prevalence increased as local host richness declined. Community disassembly was non-random: ubiquitous hosts dominating species-poor assemblages were among the most competent for vector production and virus transmission. This suggests that non-random biodiversity loss led to increased virus prevalence. Because diversity loss is occurring globally in response to anthropogenic changes, such work can inform medical, agricultural and veterinary disease research by providing insights into the dynamics of pathogens nested within a complex web of environmental forces.

Effects of Host Variability on the Spread of Invasive Forest Diseases

“…As different species show varying responses to a specific pathogen, a high species diversity will act as a sort of buffer, diluting the effects of the pathogen on the ecosystem ('diversity-disease hypothesis' or 'dilution hypothesis'; [56,57]). When pathogen transmission is density dependent or where the host range is narrow, biodiversity can alter infection prevalence through a change in the absolute abundance of important hosts and any associated vectors [58]. For example, a non-host species may reduce the probability of encountering hosts and therefore lessening opportunities for healthy susceptible individuals to become infected [56].…”

Context‐dependent effects of large‐wildlife declines on small‐mammal communities in central Kenya

“…When systematic changes in the abundance of small mammals occur following wildlife decline (as observed following experimental defaunation), this may cause increases in the risk of many rodent-borne diseases (Ostfeld andHolt 2004, Young et al 2014). Conversely, for zoonotic diseases that have high host specificity, and are primarily frequency dependent, changes in community composition and species richness observed under more intensive types of land-use conversion, particularly in agricultural sites, will likely have more profound impacts than any changes in density (Venesky et al 2013, Lacroix et al 2014. For example, several species that appear to thrive in agricultural land-uses (e.g., M. natalensis, A. nairobae) March 2015 357 CONTEXT-DEPENDENT EFFECTS OF LAND-USE are known to be excellent hosts for several regionally important human pathogens (Oguge et al 1997), and thus agricultural landscapes will likely increase prevalence of pathogens primarily hosted by these species.…”

Declines in large wildlife increase landscape-level prevalence of rodent-borne disease in Africa

“…The suggestion that anthropogenically driven wildlife declines may lead to increased disease risk in a landscape has thus generated a great deal of interest because it raises the possibility that conservation of intact natural landscapes may be an effective intervention strategy for mediating emerging threats to public health. Much of the research and debate on this relationship thus far has focused on the mechanism of transmission interference, or the process by which systematic changes in community richness (number of species), composition (identity of species), and host competence (the proportion of individuals of a species that can maintain and transmit infections) affects community competence and, ultimately, prevalence of pathogens (proportion of hosts infected) in a community, without necessarily changing the absolute abundance of susceptible hosts (individuals that can be infected by a pathogen) (15,24,25). The present study focuses primarily instead on a second, hitherto less explored pathway, susceptible host regulation, or the process by which biodiversity loss changes the abundance of susceptible hosts (26).…”