EVALUATION OF ANTIBODY TITERS TO PASTEURELLA MULTOCIDA TYPE A EXPERIMENTAL VACCINE USING HEMAGGLUTINATION TEST

摘要

Pneumonic pasteurellosis, the result of Pasteurella multocida infection of the lung, is the common final stage of Enzootic pneumonia in the porcine respiratory disease complex (PRDC). This syndrome is one of the most common and costly diseases of pigs, especially when they are raised under confinement. Published data suggest that pneumonic lesions at slaughter are very common, even in well managed herds. The P. multocida virulence factors are not well defined. In particular, the importance of the dermonecrotic toxin (DNT) remains unresolved. This toxin appears to be central for atrophic rhinitis, when only toxigenic strains of P. multocida are involved in infection, Toxigenic isolates of P. multocida from lungs have been reported (1). Since then, anumber of authors have found increasing numbers of toxigenic strains (both type A and D) in pneumonic lungs. The role, if any, of toxigenity in pneumonic pasteurellosis is still under debate. A group found that 94% of serotype A and 90% of serotype D isolates from pneumonic lungs were toxigenic (2). In contrast, other works, found no toxigenic strains (either A or D) in 218 isolates from pneumonic lungs in Spain (3). The capsule appears to be an important virulence factor, especially in serotype A, forit may help the organisms avoid phagocytosis by alveolar macrophages, at least in vitro (4, 5). Adsorption of bacterial polysaccharides to erythrocytes with the subsequent agglutination of the treated red blood cells by specific antibody, was performed with the idea to evaluate the serological response using HA following vaccination with different vaccines. An hemagglutination technique which has given specificity than previously employed serological tests is described (6).