Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: October 1, 1999
Publication Date: N/A
Technical Abstract: PRRSV, B. bronchiseptica, and P. multocida are all common agents of swine which have been implicated in the swine respiratory disease complex. Both PRRSV and B. bronchiseptica cause damage to the mucociliary and alveolar macrophage defenses of the respiratory tract, and P. multocida is a common secondary invader. Experiments with single or combination infections of PRRSV, B. bronchiseptica, and non-toxigenic P. multocida were conducted in conventional 3-week old pigs. Challenge with P. multocida alone did not result in disease or colonization of the nasal cavity, tonsil, or lung. When P. multocida was given 7 days after infection with PRRSV, there was no increase in the severity of disease over what was seen with PRRSV alone, and there was still no colonization with P. multocida. There was colonization of the nasal cavity and tonsil with P. multocida when it was given 7 days after B. bronchiseptica, but neither bacteria was isolated from the lung. Challenge with P. multocida 7 days after coinfection with PRRSV and B. bronchiseptica resulted in an increased severity of respiratory disease, increased colonization of the nasal cavity and tonsil with P. multocida, as well as isolation of all three agents from pneumonic lesions. Thus, there may be an interaction between PRRSV and B. bronchiseptica which leaves pigs especially vulnerable to infection with secondary agents such as P. multocida.