Porcine epidemic diarrhea virus (PEDV) spread rapidly after being diagnosed in the USA in April 2013. Although PEDV infection among pigs occurs predominantly by the fecal-oral route, airborne transmission of PEDV among farms has been suspected due to the rapid regional spread of PEDV, but remains unproven. Based on the hypothesis that PEDV particles can be suspended in the air and remain infectious while airborne, our objective was to determine whether infectious PEDV could be detected in air samples under both experimental and field conditions.
Air samples were collected both from a room containing experimentally infected pigs and at various distances from the outside of swine farms experiencing acute PEDV outbreaks. Air collection was conveniently performed at different locations downwind, ranging from 0.006 to 15 miles (9.6 m to 24.14 km) from each of the farms starting from the furthest distances each day. A total of 62 samples were collected, with samples stored on dry ice and submitted to the UMN VDL for PEDV RT-PCR testing. To assess the infectivity of the air samples, a bioassay consisting of inoculating susceptible piglets with the air samples was performed.
Results indicated presence of infectious PEDV in the air from experimentally infected pigs and genetic material of PEDV was detected up to 10 miles downwind from naturally infected farms. Negative control samples tested negative. Pigs infected with experimental air samples experienced moderate to severe diarrhea, with fecal number of RNA copies/mL ranging from 3.96 × 1010 to 7.57 × 1010 (Ct values ranged from 15 to 16).
Airborne transmission should be considered as a potential route for PEDV dissemination.
C Alonso, DP Goede, RB Morrison, PR Davies, A Rovira, DG Marthaler and M Torremorell. Evidence of infectivity of airborne porcine epidemic diarrhea virus and detection of airborne viral RNA at long distances from infected herds. Veterinary Research 2014, 45:73 doi:10.1186/s13567-014-0073-z