Meningoencephalomyelitis and brachial plexitis in a dog infected with louping ill virus.

A foxhound from a hunting kennel in the United Kingdom was euthanized after being hospitalized with progressive neurologic signs, including tremors, seizures, and obtunded mentation. No abnormalities were appreciated on gross postmortem examination. Histologically, severe meningoencephalomyelitis and mild neuritis of the brachial plexus were present. Molecular analysis of brain tissue detected louping ill virus. In addition, louping ill virus-specific antigens were detected in neurons within the brainstem, the entire length of the spinal cord, as well as in rare cells in the brachial plexus using immunohistochemistry. The genetic sequence of the virus appears most closely related to a previously detected virus in a dog from a similar geographic location in 2015. This is the first characterization of the inflammatory lesions and viral distribution of louping ill virus in a naturally infected dog within the spinal cord and brachial plexus.