Submitted to: Pig Veterinary Society International Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: June 6, 2000
Publication Date: September 15, 2000
Technical Abstract: Respiratory disease in pigs is arguably the most important health concern for swine producers today. Pneumonia in swine is often multifactorial, caused by infection with multiple pathogens as well as environmental and management factors. Porcine reproductive and respiratory syndrome virus (PRRSV) is a widely disseminated pathogen of swine associated with reproductive and respiratory disease. There is experimental and clinical data that PRRSV exacerbates the adverse effects of other pathogens. Bordetella bronchiseptica is also commonly found in swine and is considered a cause of bronchopneumonia and atrophic rhinitis. Infection with B. bronchiseptica predisposes pigs to disease with pathogens such as toxigenic Pasteurella multocida and Streptococcus suis. P. multocida is a common secondary invader in respiratory diseases of pigs. Since all three of these agents are common pathogens of pigs, the purpose of this study was to odetermine whether there was interaction among these agents in causing respiratory disease. These experiments demonstrated that infection with PRRSV predisposed pigs to pulmonary infection with B. bronchiseptica. PRRSV by itself did not predispose to infection with P. multocida. Prior infection with B. bronchiseptica enabled P. multocida to colonize the upper respiratory tract but did not affect the ability of these agents to gain access to the lower respiratory tract. When there was prior infection with both B. bronchiseptica and PRRSV, P. multocida was able to gain access to the lung. All three of these agents are commonly found in swine herds, thus simultaneous infection with PRRSV and B. bronchiseptica may result in severe inhibition of resistance to secondary respiratory pathogens such as P. multocida.