An update of SDEC-related research efforts on the aerobiology and biosecurity of porcine reproductive and respiratory syndrome virus and Mycoplasma hyopneumoniae

Introduction Since its emergence in the late 1980s, porcine reproductive and respiratory syndrome virus (PRRSV) has been an economically significant pathogen of pigs throughout the world. In conjunction with Mycoplasma hyopneumoniae, PRRSV has contributed to development of the porcine respiratory disease complex, resulting in poor growth rates, elevated mortality and increased cost of production. Early work by several groups indicated that elimination of PRRSV from endemically infected farms could be accomplished through several methods, including test and removal, herd closure and whole herd depopulation-repopulation. Unfortunately, due to the problem of external virus introduction (area spread), farms located in swine-dense regions of production were unsuccessful in remaining free of infection. Efforts to characterize the components of area spread of PRRSV at the University of Minnesota Swine Disease Eradication Center (SDEC) have focused on documenting the indirect routes of PRRSV transport and transmission along with the development and testing of biosecurity protocols to reduce risk. Initial studies demonstrated the ability of fomites, personnel, transport and insects to serve as vehicles for the mechanical movement of virus from infected to naive populations of pigs. In conjunction with these data, biosecurity protocols to reduce these risk factors were identified. 15-17 Unfortunately, despite rapid adaptation of this information at the farm level, the issue of area spread of PRRSV still plagued producers and practitioners’, leading to the observation from the field that airborne transmission of the virus was playing an important role in the spread of the virus between farms, particularly in swine-dense regions.