Myeloencephalitis associated with a viridans group Streptococcus in a colony of Japanese macaques (Macaca fuscata)

Five weaned immature Japanese macaques (Macaca fuscata), bred in captivity, showed nervous signs over a 12-month period. Hemorrhagic cerebral infarcts with vasculitis were detected in four necropsied animals. The distribution and nature of the lesions were consistent with bacterial embolism, and a Streptococcus isolate, biochemically similar to S. salivarius, was recovered from the cerebral lesions from three of the four necropsied macaques. Treatment with antibacterial agents (enrofloxacin) improved the clinical condition of the surviving affected animal. These observations strongly suggest that this Streptococcus spp., member of the viridans group, is responsible for this outbreak. Dental pulpitis, present in two of the four macaques, probably served as the entry for this bacterium.