Streptococcal toxic shock in a horse.

A 14-year-old horse was admitted to the veterinary hospital for treatment of tachycardia and lethargy. Initial diagnoses were ventricular tachycardia and renal dysfunction. During hospitalization other findings included fever, renal failure, hepatic failure, hypotension, and intermittent ventricular arrhythmias. Bacteriologic culture of 2 blood samples collected during febrile crises 7 days apart yielded Streptococcus mitis. These culture results along with other clinical and physical examination findings fulfill the criteria for a diagnosis of streptococcal toxic shock syndrome, previously described for humans and dogs. To our knowledge this is the first reported instance of this disease in a horse.