Perianal and tail abscessation associated with Streptococcus equi subsp. equi infection in a Quarter Horse

Summary

A 2.5‐year‐old Quarter Horse gelding presented with a history of pyrexia, suspected rectal impaction and multifocal abscessation affecting the perineum and tail base. The horse had recently been acquired from a rescue organisation, and no visible abscesses were reported at the time of acquisition. Bacterial culture of the perineal lesions identified Streptococcus equi subspecies equi ( S. equi ), which was subsequently confirmed by real‐time PCR. A guttural pouch lavage sample obtained later during hospitalisation yielded a low‐level positive qPCR result that resolved on repeat testing. Definitive evidence of internal abscessation was not identified; however, advanced imaging was not performed at admission, and additional metastatic spread could not be conclusively excluded. The gelding was managed in isolation with systemic antimicrobial therapy and topical wound care. Serial qPCR testing of abscess drainage and subsequent guttural pouch lavage samples demonstrated increasing CT values, with eventual resolution before discharge. This case describes an unusual manifestation of S. equi infection, characterised by prominent perineal and tail‐base abscessation in the absence of overt respiratory disease. The findings highlight the importance of considering S. equi in atypical lesion distributions and emphasise the need for thorough diagnostic evaluation and biosecurity measures when managing abscessative disease of unknown origin.