[Experimental study of the pathogenesis of meningitis and encephalitis during pasteurellosis in rabbits].

Pathogenesis study of encephalic and trigeminal nerve lesions in the case of rabbit pasteurellosis was done by experimental infection with P. multocida on 15 rabbits. Eight animals were infected through infraorbital nerve, four by nebulisation, two intravenously; one was used as contact control. Clinical evolutions were followed and the animals were slaughtered 4, 24, 48 and 700 h after infection. Histopathological examinations of the nasal mucosa, lung, middle ear, meninges, trigeminal nerve and liver were completed with bacteriological and electronmicroscope studies. Whatever the infection mode P. multocida could induce a temperature rise in the rabbit, and in most cases the majority of the animals had otitis media and neural lesions. This fact is in keeping with the results of our previous investigations on rabbits spontaneously infected with pasteurellosis in farms. Just four hours after experimental infection of the infraorbital nerve, Pasteurellae could induce neuritis or perineuritis up to the trigeminal root. This nerve can also be infected from the nasal mucosa following rhinitis or by haematolymphatic mode following septicaemia. Nasal cavity infection by nebulisation was followed by rhinitis in 75% of cases. They were associated with diffuse perineuritis accompanied by meningitis, encephalitis and/or otitis in two thirds of cases. With regard to pathogenesis of brain affections, trigeminal nerve lesions provoked neural lymph stagnation which induces "retrograde" centripetal circulation of this lymph up to the brain, meningitis being the first consequence. When diffuse neuritis or perineuritis reached the cerebral parenchyma, there was sometimes anatomically localised focal encephalitis.