Superspreaders have lower gut microbial alpha-diversity and distinct gut microbial composition in a natural rodent population

The microbiome is well-known to drive variation in host states (e.g., behaviour, or immunity) that would be expected to modulate the spread of infectious disease - but the role of microbiotal interactions in promoting superspreading by individuals is poorly understood. Superspreaders are individuals with a strongly disproportionate contribution to pathogen transmission, and they come in two forms. Supershedders transmit infection to more individuals because they shed higher levels of a pathogen. Supercontacters transmit infection to more individuals because they have a larger number of social contacts. We explore associations between the gut microbiota and these two forms of superspreading in a wild rodent model - Bartonella spp. bacteraemia in the field vole (Microtus agrestis). We find evidence that, first, individuals fall into distinct shedding and contacting clusters, and second, that higher-contacters have lower and more variable gut microbial alpha-diversity than lower-contacters. We also show evidence that both higher-shedders and higher-contacters have distinct gut microbial composition, and identify OTUs which are differentially abundant in the gut microbiota of these two classes of individuals when compared to lower-shedders and lower-contacters respectively. We find that the Muribaculaceae are associated with differences in both shedding and contacting, and discuss potential mechanisms by which they may be acting on these host traits.