Effects of intranasal inoculation of porcine reproductive and respiratory syndrome virus, Bordetella bronchiseptica, or a combination of both organisms in pigs

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Abstract
Objective—To examine effects of co-infection with porcine reproductive and respiratory syndrome virus (PRRSV) andBordetella bronchisepticain pigs.Animals—Forty 3-week-old pigs.Procedure—30 pigs (10 pigs/group) were inoculated with PRRSV,B bronchiseptica, or both. Ten noninoculated pigs were control animals.Results—Clinical signs, febrile response, and decreased weight gain were most severe in the group inoculated with both organisms. The PRRSV was isolated from all pigs in both groups inoculated with virus. All pigs in both groups that received PRRSV had gross and microscopic lesions consistent with interstitial pneumonia.Bordetella bronchisepticawas cultured from all pigs in both groups inoculated with that bacterium. Colonization of anatomic sites byB bronchisepticawas comparable between both groups. Pigs in the group that received onlyB bronchisepticalacked gross or microscopic lung lesions, andB bronchisepticawas not isolated from lung tissue. In the group inoculated withB bronchisepticaand PRRSV, 3 of 5 pigs 10 days after inoculation and 5 of 5 pigs 21 days after inoculation had gross and microscopic lesions consistent with bacterial bronchopneumonia, andB bronchisepticawas isolated from the lungs of 7 of those 10 pigs.Conclusions and Clinical Relevance—Clinical disease was exacerbated in co-infected pigs, including an increased febrile response, decreased weight gain, andB bronchiseptica-induced pneumonia.Bordetella bronchisepticaand PRRSV may circulate in a herd and cause subclinical infections. Therefore, co-infection with these organisms may cause clinical respiratory tract disease and leave pigs more susceptible to subsequent infection with opportunistic bacteria. (Am J Vet Res2000;61:892–899)

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