Streptococcus equi subsp. equi infection causing temporomandibular septic arthritis treated by mandibular condylectomy in a horse

Summary

A 26‐year‐old pony mare was referred for weight loss, dysphagia, lethargy and fever. Clinical examination revealed left temporal swelling, masseter muscle atrophy and malocclusion. Computed tomography examination showed severe temporomandibular joint (TMJ) alteration, extensive osteolysis of the mandibular condyle and temporal bone and concurrent temporohyoid joint involvement. Synovial fluid analysis confirmed TMJ septic arthritis, and bacterial culture and isolation identified Streptococcus equi subsp. equi . Medical management, including joint lavage and systemic and intra‐articular antimicrobials, was unsuccessful. A left unilateral mandibular condylectomy associated with disc removal was therefore performed under general anaesthesia. Postoperatively, the mare showed rapid improvement in comfort and appetite. Ten months postoperatively, mastication and body condition were normal. Septic arthritis of the TMJ is uncommon in horses but can severely impair mastication and welfare. Reported causes include penetrating trauma, fractures, iatrogenic inoculation or extension from adjacent infections. While Streptococcus equi subsp. zooepidemicus has been identified in previous cases, no cases involving Streptococcus equi subsp. equi have been reported in TMJ septic arthritis prior to the present case. This case also highlights the diagnostic value of advanced imaging, supports condylectomy as an effective therapeutic option in chronic TMJ sepsis and describes an atypical osteoarticular manifestation of strangles.