Possible mechanisms of viral-bacterial interaction in swine (literature review)

R espiratory disease is a frequent and economically significant problem in swine units. The potential loss due to decreased average daily gain and feed efficiency and the cost to prevent or treat pneumonia is substantia1,1,2 Respiratory disease caused by virus or bacteria alone can be exacerbated by a number of environmental and management factors. Numerous researchers3-14 have also shown that respiratory disease can be exacerbated by interactions of viruses and bacteria in pigs (Table 1). These interactions have also been noted in humans,15-17 mice,18-2oCOWS,21 and other animals.22-24Most studies of viral-bacterial interaction mechanisms were made in mouse models; there have been few such studies in swine. A thorough understanding of the mechanisms of viral-bacterial interactions is important to help prevent costly respiratory syndromes. This review will report the synergistic effects of viruses and bacteria in the development of respiratory disease in swine, will offer possible explanations for the cellular mechanisms that are responsible for these interactions, and will offer suggestions for the management of these viral-bacterial infections.