TMEV is indigenous to mice only. In natural infections, clinical signs are very rare. In experimental infections, CNS signs can occur irrespective of the route of inoculation, but occur most frequently after mice are inoculated with virus intracerebrally.
Morbidity is highest in suckling mice.
Histological examination of spinal cords from these mice found poliomyelitis. Some of the mice that survived became seropositive. Usually, the prevalence of positives was low and reaction intensities were weak. Natural TMEV infections of rats have not been reported in the scientific literature.