Recurrent outbreak of Streptococcus bovis/Streptococcus equinus complex-associated meningoencephalitis in farmed mink

The Streptococcus bovis/Streptococcus equinus complex (SBSEC) is part of the normal gastrointestinal microflora in animals and humans but is an opportunistic pathogen that has been implicated in meningitis, endocarditis and septicaemia. There is only one report of SBSEC causing disease (endocarditis) in mink. This case report describes two outbreaks of SBSEC infection in farmed mink occurring 1 year apart at the same facility. In both cases, affected mink had neurological signs prior to death and the mortality level was 5,000 (2021) and 500 (2022) out of 100,000 mink. Necropsy findings included hepatomegaly, splenomegaly and congested lungs. Histopathology revealed suppurative meningoencephalitis and neutrophilic inflammation in the lungs, liver and kidneys. Aerobic bacterial culture identified SBSEC isolates in the brain and liver. This is the first report to implicate SBSEC in meningoencephalitis and septicaemia in farmed mink.