Possible canine source of Streptococcus equi subspecies zooepidemicus causing meningitis in an infant

Streptococcus equi subspecies zooepidemicus (S. zooepidemicus) is a pathogen that colonizes and causes disease in horses, and less commonly, in other mammals. This zoonotic disease in humans is rare. In the reported human cases, it has caused bacteremia, endocarditis, arthritis and meningitis, and it has been linked to contact with horses or ingestion of unpasteurized dairy products. We report a case of a six-month-old female patient who presented with a one-day history of fevers and neurological symptoms. Blood and cerebrospinal fluid cultures revealed S. zooepidemicus, and brain imaging showed a subdural fluid collection and diffuse brain infarcts. Exposure history suggested a canine source as patient had close contact with two dogs that had respiratory infections but no contact with other pets including horses. She had clinical and radiographic improvement after a four-week course of penicillin G and drainage of a subdural fluid collection but she had residual severe to profound hearing loss and mild neurocognitive deficits. This case report provides the third reported case of possible S. zooepidemicus transmission from dogs to humans, and the second such case that has led to meningitis. Clinicians and public health practitioners should recognize that S. zooepidemicus may be transmitted from dogs and can lead to severe disease in humans.