The pathogenicity of Haemophilus somnus in various laboratory animal species.

As a test of susceptibility of laboratory animals to the causative organism of thrombotic meningoencephalitis of cattle, young mice, rats, rabbits, piglets, chicks and hamsters were exposed to the virulent strain 43826 of Haemophilus somnus by the intravenous and intraperitoneal routes. Only the hamsters developed lesions attributable to the organism. Two of ten hamsters developed an acute orchitis and epididymitis characterized by necrosis and arteritis. The fact that Histophilus ovis, a cause of epididymitis in Australian and New Zealand rams, is apparently very closely related to Haemophilus somnus suggests that the hamster may be a useful laboratory model to study this disease.