The impact of animal age, bacterial coinfection, and isolate pathogenicity on the shedding of porcine reproductive and respiratory syndrome virus in aerosols from experimentally infected pigs.

The objective of this study was to evaluate the role of different variables (animal age, bacterial coinfection, and isolate pathogenicity) on the shedding of Porcine reproductive and respiratory syndrome virus (PRRSV) in aerosols. Animals were grouped according to age (2 versus 6 mo) and inoculated with a PRRSV isolate of either low (MN-30100) or high (MN-184) pathogenicity. Selected animals in each group were also inoculated with Mycoplasma hyopneumoniae. The pigs were anesthetized and aerosol samples (1000 breaths/sample) collected on alternating days from 1 to 21 after PRRSV inoculation. The results indicated that animal age (P = 0.09), M. hyopneumoniae coinfection (P = 0.09), and PRRSV isolate pathogenicity (P = 0.15) did not significantly influence the concentration of PRRSV in aerosols. However, inoculation with the PRRSV MN-184 isolate significantly increased the probability of aerosol shedding (P = 0.00005; odds ratio = 3.22). Therefore, the shedding of PRRSV in aerosols may be isolate-dependent.