Demographic and ecological drivers of infectome diversity in companion cats

Cats ( Felidae ) have become an integral part of many households, with close physical interaction between cats and their owners through activities like petting, kissing, and being licked on the cheek and hands. However, our understanding of the full spectrum of pathogens affecting cats (referred to as the infectome) is limited, mainly due to the inadequacy of commonly used diagnostic tools in capturing the complete diversity of potential pathogens and the prevalence of pathogen co-infections. In this study, we employed a meta-transcriptomic approach to simultaneously characterize the infectome contributing to different disease syndromes and to investigate spatial, demographic, and ecological factors influencing pathogen diversity and community composition in a cohort of 27 hospitalized cats and seven stray cats. We identified 15 species of pathogens, with Candidatus R.tarasevichiae and T. foetus representing potential spillover risks. Importantly, although most cases of ascites hyperplasia were explained by coinfection with multiple pathogens, we identified the potential novel clinical outcome of M. aubagnense infection among cats. We demonstrated that the rise of infectome diversity can be explained by a variety of predictors including age growth, temperature increase, and a higher proportion of females, with age growth presenting the strongest effect. Fine-scale analysis indicated a higher diversity of infectome were harbored in juvenile cats rather than adults. Our results demonstrated that most cat diseases are better explained by the presence of virus-bacteria or virus-virus coinfection. Furthermore, our results highlight the cross-species risks in cat pathogens. Importantly, we showed the value of linking the modern influx of meta-transcriptomics with comparative ecology and demography, and of utilizing it to affirm that ecological and demographic variation not only impact the single-pathogen model but also the total infectome. ### Competing Interest Statement The authors have declared no competing interest.