Recovery Of Novel Presumptive Horse Thrush-Causing Bacteria, Vagococcus Sp. And Corynebacterium Sp., In Rodeo Horses

Bacteria-attributed thrush infections of horse hoofs could be detrimental to animal performance. Fusobacterium necrophorum (leukotoxin-positive, lktA + ) and Dichelobacter nodosus (fimbrialprotease-exporter-positive, fimA + ) bacteria were documented to associate with thrush symptomatic horse positively (i.e., partially) and negatively, respectively, following genespecific PCR detections. However, the availability of non-F. necrophorum bacteria in horse thrush has been unexplored to date. The present study explored thrush prevalence and its associated bacteria in rodeo horses. A total of 16 separate swabbed and non-swabbed (i.e., scraped frog skin) samples were randomly acquired from rodeo horses of three independent open pen raisers between September 2022 and May 2023. Hoof’s indigenous bacterial suspensions were cultivated anaerobically and aerobically, and isolated colonies were separately streaked for purification. Bacterial genomes were extracted using the bead collision method and identified using 16S rRNA gene sequencing. Of 16 hoof samples, 11 were healthy and five were sickened, and the latter were more prevalent at moderate temperature (i.e., 75-85 °F, 67%) or combined moderate and dry conditions (67%). 41 phenotypically-variant bacteria were differentially detected in healthy (30) and sickened (11) hoofs. Of 18 bacterial DNAs analyzed, six (33%) lktA positive isolates, presumptive of F. necrophorum availability, were from healthy (5) and sickened (1) hoofs. Subsequently, 16S rRNA bacterial identification exhibited non-F. necrophorum bacteria, including animal/human pathogens. The present comparative study reveals potential positive correlations (i.e., odds ratio>1) between thrush prevalence and ambient conditions (i.e., temperature and humidity). This discovery could improve currently emerging thrush management knowledge and prevent infection-associated performance and prolonged chemical treatment complications.