Association and Host Selectivity in Multi-Host Pathogens

Abstract

The distribution of multi-host pathogens over their host range conditions their population dynamics and structure. Also, host co-infection by different pathogens may have important consequences for the evolution of hosts and pathogens, and host-pathogen co-evolution. Hence it is of interest to know if the distribution of pathogens over their host range is random, or if there are associations between hosts and pathogens, or between pathogens sharing a host. To analyse these issues we propose indices for the observed patterns of host infection by pathogens, and for the observed patterns of co-infection, and tests to analyse if these patterns conform to randomness or reflect associations. Applying these tests to the prevalence of five plant viruses on 21 wild plant species evidenced host-virus associations: most hosts and viruses were selective for viruses and hosts, respectively. Interestingly, the more host-selective viruses were the more prevalent ones, suggesting that host specialisation is a successful strategy for multi-host pathogens. Analyses also showed that viruses tended to associate positively in co-infected hosts. The developed indices and tests provide the tools to analyse how strong and common are these associations among different groups of pathogens, which will help to understand and model the population biology of multi-host pathogens.

Evolution and Emergence of Plant Viruses

“…In fact, the hypothesis that generalism pays a cost is supported by evidence that generalist viruses able of infecting a large number of hosts with equal efficiency seems not to be the norm. Thus, the prevalence of five generalist viruses in 21 wild plant species showed significant host-virus associations, indicating host selectivity as a strategy in these generalist viruses (Malpica et al, 2006). Also, host selectivity was shown for BYDV over different grass species (Power et al, 2011).…”

“…In an exhaustive analysis of the incidence of five viral species in 21 wild plant species, Malpica et al (2006) found that the prevalence of certain viruses was not independent from the prevalence of other viruses; certain combinations appeared more frequently than expected by share chance. In an individual host, coinfection may have variable consequences, from the development of milder symptoms to their exacerbation (Hammond et al, 1999).…”

Highly Diverse Morbillivirus-Related Paramyxoviruses in Wild Fauna of the Southwestern Indian Ocean Islands: Evidence of Exchange between Introduced and Endemic Small Mammals

“…Different factors that may drive the observed levels of high genetic diversity of paramyxoviruses include the following: (i) the inherent genetic drift associated with many RNA viruses (42), which alone may be insufficient to explain high genetic variation between closely related viral lineages; (ii) coinfection within individual hosts, which is a "prerequisite for genetic exchange between different pathogen species or strains" (43), was observed in this and other studies of novel Paramyxovirus genera (2-4), and the possibility of recombination events between highly similar viruses should not be excluded, although their observation is rare for members of the Paramyxoviridae; and (iii) viral adaptation due to exchange within multihost systems (18).…”

Arabidopsis thaliana as a model for the study of plant–virus co-evolution

“…We focused on five virus species that were selected by having different life histories, and that had been previously reported infecting wild species of the Brassicaceae in Europe (Pallett et al 2002;Sánchez et al 2007) and/or in Central Spain (Sacristán et al 2004;Malpica et al 2006;Pagán & García-Arenal 2010, unpublished results). We chose six A. thaliana populations located in different habitats.…”