Relationship between two pathogens in an amphibian community that experienced mass mortalities

Because host species tend to harbor multiple parasitic species, coinfection in a host is com-mon. The chytrid fungusBatrachochytrium dendrobatidis(Bd) and the viruses in the genusRanavirus(Rv) are responsible for the decline of amphibians worldwide. Despite widegeographical co-occurrence and the serious conservation problem that coinfection withthese pathogens could represent, little is known about their possible synergistic interac-tions and effects in a host community. We investigated the occurrence and associationsbetween these two pathogens in an amphibian community after Rv-driven disease out-breaks were detected in four populations of the Iberian ribbed newt (Pleurodeles waltl)innorthwestern Spain. We collected tissue samples from amphibians and fish and estimatedBd and Rv infection loads by qPCR. A few months after the most recent mass mortalityevent, Rv infection parameters at the affected sites decreased significantly or were lowerthan such registered at the sites where no outbreaks were recorded. Both pathogens weresimultaneously present in almost all sites, but coinfection in a single host was rare. Ourfindings suggest that the co-occurrence of Bd and Rv does not predict adverse outcomes(e.g., enhanced susceptibility of hosts to one pathogen due to the presence or infectionintensity of the other) following an outbreak. Other variables (such as species identity orsite) were more important than infection with a pathogen in predicting the infection statusand severity of infection with the other pathogen. Our results highlight the importance ofhost-specific and environmental characteristics in the dynamics of infections, coinfectionpatterns, and their impacts.info:eu-repo/semantics/publishedVersio