The pathology of pneumonia in the pig

The literature dealing with pneumonia in the pig was reviewed, placing emphasis on the reports concerning the status of pigs pneumonias in Britain but referring also to work In other countries where it was relevant. She main objects of the thesis ware (a) to study the histopathological naturally oocurring in the lungs of pigs with naturally occurring pneumonia with a to classifying the lesions on this basis, (b) to study the pathogenesis of enzootic pneumonia in experimental animals (c) to investigate the relationship between Pasteurella multocida, Haeiao phis. parainflueniaa and pneumonia in the pig (d) to study the pathogenesis of the pneumonia due to Metastrongylus apri in experimental animals and (a) to vaccinate young pigs against the pig lungworm M. apri using x- irradiated infective larvae of M, apri. The naturally occurring pneumonias studied consisted of 576 sets of pneumonic lungs from pigs of all ages, which were obtained from three sources (i) pigs sent to the post-mortem room at the Veterinary Hospital, the University of Glasgow, for routine post-mortem examination, (ii) pigs - 2 - dying or destroyed on farms during the investigation of respiratory dis-ease problems in the field, (iii) pigs killed in abattoirs. As a result of studying these lungs hiotopathologically the pulmonary lesions were classified into the following groups, enzootic pneumonia, interstitial pneumonia, pneumonia duo to H. parainfluenza, simple acute bronchopneumonia necrotising bronchopneumonia, suppurative bronchopneumonia, embolic pneumonia, tuberculosis, pneumonia due to M. apri, pulmonary toxoplasmosis, giant cell pneumonia and pulmonary vascular lesions. Enzootic pneumonia, interstitial pneumonial the pneumonia due to parainfluenza and the pneumonia due to M. apri were studied in experimental animals. Enzootic pneumonia was produced experimentally in pigs using sus-pensions of pneumonic lung injected intratracheally. These animals were killed at different time intervals after infection and the serial pathology of the disease was described. The significance of three of the important features of the pneumonia namely alveolar cell hyperplasia, peribronchiolar lymphoid nodular development and alveolar collapse was discussed, and a hypothesis was advanced to explain the pathogenesis of the pulmonary lesions. Interstitial pneumonia was regularly associated with P. multocida but attempts to produce the pneumonia experimentally in pigs using pure cultures of the organism were unsuccessful. It was demonstrated, however, that H. parainfluenza could produce pneumonia in experimentally infected pigs identical to that occurring in the field. A survey was carried out to determine the incidence of lungworms in the pigs being sent to an abattoir in central Scotland and 93 of 1,113 sets of lungs examined were found to contain lungworms giving an incidence of 8.4%. The lungworms collected during this survey were used to infect cultures of the earthworm Elsenia foetida which in common with several other species of earthworms, is the intermediate host for this parasite. Pigs were infected with known numbers of larvae, obtained from the earth-worms, and were killed serially so that the pathogenesis of the disease could be studied. before x-irradiation could be used to attenuate larvae for vacating pigs against M. apri it was necessary to discover the most suitable level of x-irradiation. This was done by infecting four groups of pigs with normal larvae, larvae given 20kr of x-irradiation, larvae given 40kr of x-irradiation and larvae given 60kr of x-irradiation. The most suitable level as judged by (a) the number of worms at autopsy and (b) the degree of clinical disturbance was found to be 60kr. Using the information gained from the previous experiment a group of young pigs was vaccinated with infective larvae which had been previously irradiated with 60kr of x-rays. When the animals were killed after they were challenged with normal larvae, it was found that the results of the experiment were inconclusive