Data from: Ranavirus epizootics and gut bacteriome dysbiosis in tadpoles: evidence for the Anna Karenina Principle?

Host-associated microbial communities (microbiomes) play critical roles in
animal health and disease, yet their responses to pathogens under natural
conditions remain poorly understood. We investigated gut bacterial
community (bacteriome) dynamics in wood frog (Rana sylvatica [Lithobates
sylvaticus]) tadpoles during natural ranavirus outbreaks to understand how
pathogen-induced disturbances shape microbiome diversity, composition, and
function. Using 16S rRNA sequencing, we compared the bacteriomes of
tadpoles in ponds experiencing ranavirus-induced die-offs with those from
unaffected reference ponds before, during, and after mortality events.
Ranavirus infection significantly altered gut bacteriome composition and
increased microbiome variability (dispersion), consistent with the Anna
Karenina Principle. Tadpoles with high infection intensities exhibited
reduced bacterial diversity and pronounced shifts in community structure,
characterized by enrichment of specific taxa such as Cetobacterium and
Turicibacter, which have been linked previously to antiviral immunity and
gut health. Predicted functional analyses revealed shifts toward
carbohydrate metabolism pathways during die-offs, suggesting microbial
adaptation to altered host physiology under infection stress. Notably,
bacteriome disruptions were detectable even before die-offs occurred,
highlighting potential early-warning microbiome indicators of infection.
In one recovering population post-epizootic, we observed partial recovery
of the bacteriome, indicating potential microbial resilience. Our findings
demonstrate that ranavirus epizootics profoundly disrupt gut microbiomes
in wild amphibian populations while simultaneously eliciting potentially
adaptive microbial responses. These insights underscore the complex
interplay between host immunity, microbiome dynamics, and environmental
conditions during disease outbreaks, highlighting opportunities for
microbiome-based interventions to support amphibian conservation.