Applied epidemiology of the pathogens involved in porcine respiratory disease complex

Swine influenza A viruses (swIAv), porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2 (PCV2), Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae are the main infectious agents involved in porcine respiratory disease complex (PRDC). Their conditions for spread and persistence in pig populations are mainly related to host or pathogen interactions and the features of pig population dynamics. The resulting endemic persistence in pig farms leads to complex interactions between those viruses and bacteria governing the severity of PRDC and the ability to control the clinical consequences in pig farms. Implications of the specific epidemiology of these infectious agents are discussed in this paper in the perspective of potential strategies for a better control.