Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: February 22, 1999
Publication Date: N/A
Co-infection with two or more respiratory pathogens is a common cause of pneumonia in grow-finish swine. The effect of co-infection of PRRSV and B. bronchiseptica was examined in thirty, 3-week-old weaned pigs (10 pigs per group) that were inoculated with PRRSV, B. bronchiseptica, or PRRSV and B. bronchiseptica. An additional 10 pigs served as uninoculated controls. Clinical signs, febrile response, and decreased weight gain were more severe in the co-inoculated group than in the other groups. Five pigs from each group were euthanized at 10 and 21 days post inoculation. PRRSV was isolated from all pigs in both groups inoculated with the virus. All pigs in the two groups which received PRRSV had gross and histopathologic lesions consistent with interstitial pneumonia. B. bronchiseptica was cultured from the nasal turbinates and trachea of all pigs in both groups inoculated with the bacteria. Colonization of these anatomic sites by B. bronchiseptica was comparable between the two groups. Pigs in the group which received only B. bronchiseptica lacked gross or histopathological lung lesions, and B. bronchiseptica was not cultured from lung tissue. In the group inoculated with B. bronchiseptica and PRRSV, 3 of 5 pigs at 10 days post infection and 5 of 5 pigs at 21 days post infection had gross and histopathologic lesions consistent with bacterial bronchopneumonia, and B. bronchiseptica was isolated from the lungs of 6 of these 10 pigs. Thus, there appeared to be exacerbation of disease in the co-infected group, especially with regard to induction of lung lesions due to B. bronchiseptica.