The experimental infection of calves with a British strain of Haemophilus somnus.

Intravenous inoculation of a British strain of Haemophilus somnus resulted either in fatal peracute or chronic forms of H somnus disease. Pleuritis, pericarditis and arthritis were prominent post mortem findings. Intratracheal inoculation led to severe cellulitis and abscess formation in the neck with acute suppurative bronchopneumonia in one calf, while in another, encapsulated abscesses and pleural adhesions were seen. Intraperitoneal inoculation resulted in fatal fibrinous peritonitis in one calf. The organism was readily recovered from the lesions except when overgrown by post mortem contaminants. Rising antibody titres were detected in two calves 12 days after inoculation by a micro-complement fixation test, and the organism was demonstrated in synovial fluid by an indirect fluorescent antibody test. No organisms were recovered from and no lesions were seen in the nervous tissues of the calves in contrast to studies of this disease in the USA.