Biology subjects

Sergeant, C.

Publications and source records attributed to Sergeant, C..

3 recordsLinked to original sources

bioRxiv2025

Host species composition, not priority effects, determines infection risk in multihost-multiparasite amphibian communities

Novel parasite emergences are posing uncertain threats to wildlife communities worldwide. Because parasites typically infect multiple host species and interact with other parasites, the degree of threat posed by these emergences is known to depend both on a communitys host species composition and history of exposure to other parasites. What is not known is how these two factors - multi-host effects and multi-parasite effects - interact to shape the outcomes of parasite emergences. We experimentally investigated the outcomes of sequential emergences by two amphibian parasites of major concern to global biodiversity, Batrachochytrium dendrobatidis (Bd) and Ranavirus (Rv). Mimicking sequential Bd and Rv emergence in communities comprising either larval common toads (Bufo bufo), larval common frogs (Rana temporaria), or both host species, showed that host community composition influenced subsequent patterns of Bd and Rv infection much more than the presence of the other parasite. Bd prevalence varied predictably with host community composition; toads exhibited consistently higher Bd infection probabilities than frogs across all scenarios. Variation in community-level prevalence therefore was explained by differences in the relative abundance of toads. In contrast, community-level Rv prevalence was not consistently driven by a single host species. Going from single-host to two-host communities reversed relative Rv infection probabilities in frogs versus toads; when kept separately, frogs had a higher Rv infection probability than toads, but toads had a higher infection probability than frogs when the two species were co-housed. Host species composition can therefore alter multi-parasite infection dynamics not only through changes in the abundance of primary host species, but also through changes in which species appear to act as the primary hosts. These insights suggest that Bd-Rv dynamics in single-host scenarios may not reflect those occurring in natural multihost communities, and the observed context-dependency in the apparent primary host species for Rv highlights an overlooked factor potentially shaping biodiversity-disease relationships.

ecology↗

bioRxiv2018

Temperature is a key driver of a wildlife epidemic and future warming will increase impacts

Increasing environmental temperatures are predicted to have increasingly severe and deleterious effects on biodiversity. For the most part, the impacts of a warming environment are presumed to be direct, however some predict increasingly severe disease epidemics, primarily from vector-borne pathogens, that will have the capacity to deplete host populations. Data to support this hypothesis are lacking. Here we describe increasing severity of ranavirosis driven by increasing temperature affecting a widely distributed amphibian host. Both in vitro and in vivo experiments showed that increasing environmental temperature leads to increased propagation of ranavirus and, in the latter, increased incidence of host infection and mortality. Also, temperature was shown to be a key determinant of disease dynamics in wild amphibians, raising the odds and severity of disease incidents. The direction of this effect was highly consistent in the context of other interacting variables such as shading around ponds. Projections based on future climate indicate that changes in seasonal weather in the UK will result in the increased incidence of severe cases of ranavirosis in amphibian populations that could affect recruitment. These complementary lines of evidence present a clear case of direct environmental modulation of a host-pathogen interaction and provide information for proposing mitigation actions.

epidemiology↗

bioRxiv2017

Host Microbiome Richness Predicts Resistance to Disturbance by Pathogenic Infection in a Vertebrate Host

Environmental heterogeneity is known to modulate the interactions between pathogens and hosts. However, the impact of environmental heterogeneity on the structure of host-associated microbial communities, and how these communities respond to pathogenic exposure remain poorly understood. Here we use an experimental framework to probe the links between environmental heterogeneity, skin microbiome structure and infection by the emerging pathogen Ranavirus in a vertebrate host, the European common frog (Rana temporaria). We provide evidence that environmental complexity directly influences the diversity and structure of the host skin microbiome, and that more diverse microbiomes are more resistant to perturbation associated with exposure to Ranavirus. Our data also indicate that host microbiome diversity covaries with survival following exposure to Ranavirus. Our study highlights the importance of extrinsic factors in driving host-pathogen dynamics in vertebrate hosts, and suggests that environment-mediated variation in the structure of the host microbiome may covary with observed differences in host susceptibility to disease in the wild.

ecology↗