Long-distance airborne transport of infectious PRRSV and Mycoplasma hyopneumoniae from a swine population infected with multiple viral variants

Airborne transport of porcine reproductive and respiratory syndrome virus (PRRSV) and Mycoplasma hyopneumoniae (M hyo) has been reported out to 4.7 km. This study attempted to determine whether this event could occur over longer distances and across multiple viral variants. To accomplish this goal, a mixed infection of 3 PRRSV variants (1-8-4, 1-18-2 and 1-26-2) and M hyo 232 was established in a source population of growing pigs. Over 21-day period, air samples were collected from the source population and at designated distances from the herd. Samples were tested for PRRSV RNA and M hyo DNA by PCR and if positive, further characterized. In exhaust air from the source population, PRRSV and M hyo were detected in 21 of 21 and 8 of 21 air samples, respectively. Five of 114 (4.4%) long-distance air samples were positive for PRRSV and 6 of 114 (5.2%) were positive for M hyo. The 5 PRRSV-positive samples were collected at 2.3, 4.6, 6.6 and 9.1 km from the herd. All contained infectious virus and were >99.2% homologous to PRRSV 1-8-4. No evidence of PRRSV 1-18-2 or 1-26-2 was detected in long-distance samples. All 6 M hyo-positive samples were 99.9% homologous to M hyo 232 and 3 samples (collected at 3.5, 6.8 and 9.2 km from the herd) were infectious. These results indicate that airborne transport of PRRSV 1-8-4 and M hyo 232 occurs over longer distances than previously reported and that both pathogens remained infectious.