An Etiological Study Of Equine Acute Colitis: Microbiome Composition And Reporting Guidelines

Equine acute typhlocolitis is an important disease with significant morbidity and mortality, for which the clinical diagnosis and medical management continue to be a challenge. The overall goal of this study was to investigate the etiological causes of enterotyphlocolitis in horses undergoing postmortem investigation and to propose testing and histopathological reporting guidelines. It also aimed to further investigate the gastrointestinal microbiota composition of horses that succumbed to acute typhlocolitis through culture-enriched 16S rRNA gene sequencing. This study had similar results when compared to other studies in other geographical areas, in which 50 % of the cases of enterotyphlocolitis did not have a confirmed etiological diagnosis. Culturomics analysis of the cecal content of horses with and without typhlocolitis showed that alpha diversity significantly decreased in horses diagnosed with acute typhlocolitis, and the phylum Fusobacteriota was identified as being more predominant in diseased horses. Targeted bacterial culture significantly influenced the results of gene sequencing and provided more specific and detailed information about the microbial composition. In addition, our study investigated the prevalence of Clostridium innocuum in horses with colitis and in healthy horses and found a similar prevalence of this bacterium in both populations. This thesis highlights the deficiencies and challenges of investigating the etiological agents that cause acute colitis, as well as it is the first study to demonstrate that culture-enriched sequencing is a viable additional approach to the analysis of the equine gut microbiota.