EFFECTS OF INTRANSAL INOCULATION WITH BORDETELLA BRONCHISEPTICA, PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME VIRUS, OR A COMBINATION OF BOTH ORGANISMS ON SUBSEQUENT INFECTION WITH PASTEURELLA MULTOCIDA IN PIGS

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

Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/23/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Respiratory disease in pigs is arguably the most important health concern for swine producers today. Porcine reproductive and respiratory syndrome virus (PRRSV), Bordetella bronchiseptica, and Pasteurella multocida are common infectious agents of swine that are associated with swine respiratory disease. Both PRRSV and B. bronchiseptica impair the defense mechanisms in the respiratory tract. The role of P. multocida in respiratory disease is as a secondary invader. The purpose of this experiment was to determine whether PRRSV and/or B. bronchiseptica predispose to infection with P. multocida. Challenge with P. multocida alone did not result in infection, and pre-infection with PRRSV did not predispose to infection with P. multocida. B. bronchiseptica predisposed to infection of the upper respiratory tract but not the lung with P. multocida. When pigs were infected with both PRRSV and B. bronchiseptica prior to challenge with P. multocida, there was increased infection of bot the upper respiratory tract and lung with P. multocida. Thus, there may be interaction between PRRSV and B. bronchiseptica which leaves pigs especially vulnerable to pulmonary infection with secondary agents such as P. multocida. Control of these organisms is important in maintaining respiratory health in pigs.

Technical Abstract: Porcine reproductive and respiratory syndrome virus (PRRSV), Bordetella bronchiseptica and Pasteurella multocida are common infectious agents of swine that are associated with swine respiratory disease. Both PRRSV and B. bronchiseptica impair the mucociliary and alveolar macrophage defense mechanisms in the respiratory tract. The role of P. multocida in respiratory disease is as a secondary invader. Experiments with single or combination infections of PRRSV, B. bronchiseptica, and non-toxigenic P. multocida were conducted in 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 interaction between PRRSV and B. bronchiseptica which leaves pigs especially vulnerable to infection with secondary agents such as P. multocida.