EN
The toxin used was a sterile crude extract of a sonicated strain A11/2a of Pasteurella mutocida (P.m.) type D, isolated from a pig with atrophic rhinitis. Fifteen rabbits aged 8—12 days were being given 8 or 12 doses of the toxin every 3—4 days intramuscularly or subcutaneously. According to the same schedule 9 control litter-mates were being given an extract from the nontoxigenic strain 01d9 of P.m., type D. All the rabbits were then sacrificed, necropsied and the specimens were taken for histopathological evaluation and the nasal swabs for bacteriological examination. No toxigenic P.m. or Bordetella bronchiseptica were isolated from those animals as tested by the guinea pig skin test. All the rabbits which had received the toxin showed from mild to severe atrophy of the nasal turbinates. Microscopic lesions included degeneration of their osseous core, necrotic changes of the osteocytcs and an increased number of osteoblasts and osteoclasts. Hyperaemia of the nasal mucosa was also seen and in a few cases bionecrosis was found in the osteoblasts. Degeneration was found in the liver and myocardium. In the lymphatic tissue hypertrophy of the follicles was observed. Control rabbits showed no changes with the exception of one animal with mild turbinate atrophy. It is concluded that in natural atrophic rhinitis in rabbits the dermonecrotic toxin of P.m. plays a similar role as in this kind of disease in pigs.