EFFECTS OF INTRANASAL INOCULATION OF PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME VIRUS, BORDETELLA BRONCHISEPTICA, OR A COMBINATION OF BOTH ORGANISMS IN PIGS

Authors: Brockmeier, Susan; Palmer, Mitchell; Bolin, Steven - Steve

Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/21/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Co-infection with two or more respiratory pathogens is a common cause of pneumonia in swine. This condition, termed the porcine respiratory disease complex, has become one of the most important health concerns for swine producers. Porcine reproductive and respiratory syndrome virus (PRRSV) is a widely disseminated pathogen of swine capable of causing reproductive and respiratory disease. There is experimental and clinical evidence that PRRSV is associated with outbreaks of other pathogens. Bordetella bronchiseptica also is widely found in pig herds. B. bronchiseptica can cause primary bronchopneumonia in young pigs and may be a secondary pathogen of the lung in older animals. The purpose of this study was to determine whether co-infection with PRRSV and B. bronchiseptica would result in more severe disease than with either agent alone. Clinical signs, febrile response, and decreased weight gain were more severe in the co-inoculated group than in the other groups. Pigs in the group which received only B. bronchiseptica lacked lung lesions and B. bronchiseptica was not cultured from lung tissue. In the group inoculated with B. bronchiseptica and PRRSV, 8 of 10 pigs had lesions consistent with bacterial bronchopneumonia, and B. bronchiseptica was isolated from the lungs of 7 of those 10 pigs. Both B. bronchiseptica and PRRSV may circulate within a herd subclinically, and co-infection may cause clinical respiratory disease and leave pigs more susceptible to further infection with opportunistic bacteria. Control of these organisms may be important in maintaining respiratory health in pigs.

Technical Abstract: A study was conducted to examine the effects of co-infection of porcine reproductive and respiratory syndrome virus (PRRSV) and Bordetella bronchiseptica in pigs. Thirty pigs (10 pigs per group) were inoculated with PRRSV, B. bronchiseptica, or PRRSV and B. bronchiseptica. Ten pigs were kept as non-inoculated controls. Clinical signs, febrile response, and decreased weight gain were more severe in the co-inoculated group than in the other groups. 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 microscopic lesions consistent with interstitial pneumonia. B. bronchiseptica was cultured from the nasal turbinates and trachea of all pigs in both groups inoculated with that bacterium. 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 microscopic 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 microscopic lesions consistent with bacterial bronchopneumonia, and B. bronchiseptica was isolated from the lungs of 7 of those 10 pigs. There was exacerbation of disease in the co-infected group, especially with regard to induction of lung lesions due to B. bronchiseptica. Both B. bronchiseptica and PRRSV may circulate within a herd subclinically, and co-infection may cause clinical respiratory disease and leave pigs more susceptible to further infection with opportunistic bacteria.