title: Airborne transmission of Actinobacillus pleuropneumoniae and porcine reproductive and respiratory syndrome virus in nursery pigs.
abstract: OBJECTIVE
  To document airborne transmission of Actinobacillus pleuropneumoniae and porcine reproductive and respiratory syndrome virus (PRRSV) infection in nursery pigs.
  
  
  METHODS
  32 two-week-old pigs obtained from 3 farms, but with similar Landrace X Yorkshire genetics for trial 1 of each experiment; 16 pigs for trial 2 of the A pleuropneumoniae experiment; and 14 pigs for trial 2 of the PRRSV experiment.
  
  
  METHODS
  In experiment 1, pigs were inoculated with A pleuropneumoniae serotype 1 (6/8) or were left as contacts (2/8). At the beginning of trial 1, pigs were seronegative to A pleuropneumoniae serotypes 1 and 5 on the basis of results of an ELISA, but had positive results on the A pleuropneumoniae hemolysin I (Apx1)-neutralization test. Pigs in trial 2 had negative results on both tests. Pigs of trial 1 of experiment 2 were inoculated with a PRRSV virulent field isolate (MN-1b); pigs of trial 2 were inoculated with the virus reference strain VR-2332. Aerosol-exposed pigs were placed on the other side of the air duct and kept there for 2 to 7 weeks depending on evidence of airborne transmission.
  
  
  RESULTS
  In trial 1 of experiment 1, evidence of airborne transmission was not found. In trial 2, most airborne-exposed pigs died as a result of A pleuropneumoniae infection 12 days after initiation of the experiment. In trial 1 of experiment 2, all inoculated pigs (8/8) seroconverted, but only 2 of 8 contact-exposed pigs seroconverted. Aerosol-exposed pigs did not seroconvert nor was virus isolated. In trial 2, all inoculated and contact-exposed pigs seroconverted. All aerosol-exposed pigs seroconverted after 21 days, and virus was isolated at 16 days.
  
  
  CONCLUSIONS
  A pleuropneumoniae was transmitted by air at a distance of 1 m when pigs were fully susceptible to the organism. Transmission of PRRSV appeared to be strain dependent; when reference strain VR-2332 was used, airborne transmission of PRRSV was documented.
authors.affiliation: Department of Clinical and Population Sciences, College of Veterinary Medicine, University of Minnesota, St Paul 55108, USA.
authors.forename: M
authors.initials: M
authors.lastname: Torremorell
authors.forename: C
authors.initials: C
authors.lastname: Pijoan
authors.forename: K
authors.initials: K
authors.lastname: Janni
authors.forename: R
authors.initials: R
authors.lastname: Walker
authors.forename: H S
authors.initials: HS
authors.lastname: Joo
mesh_terms: D000189:Actinobacillus Infections / Q000635:transmission / Q000662:veterinary*; D016977:Actinobacillus pleuropneumoniae / Q000145:classification; D000391:Air Microbiology; D000818:Animals; D006799:Housing, Animal; D008834:Microclimate; D019318:Porcine Reproductive and Respiratory Syndrome / Q000635:transmission*; D012703:Serotyping; D013552:Swine; D013553:Swine Diseases