US research focuses on airborne transport of PRRS and M. hyo in pigs

Researchers from the Swine Disease Eradication Center from the University of Minnesota in the US studied the long-distance airborne transport of infectious PRRS virus 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 4.7km. 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 PRRS virus 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 PRRS virus RNA and M. hyo DNA by PCR and if positive, further characterized. In exhaust air from the source population, PRRS virus 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 PRRS virus and 6 of 114 (5.2%) were positive for M. hyo. The 5 PRRS virus-positive samples were collected at 2.3, 4.6, 6.6 and 9.1km 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 9.2km 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.