AIRBORNE TRANSMISSION OF ACTINOBACILLUS-PLEUROPNEUMONIAE AND PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME VIRUS IN NURSERY PIGS

Objective-To document airborne transmission of Actinobacillus pleuropn eumoniae and porcine reproductive and respiratory syndrome virus (PRRS V) infection in nursery pigs. Animals-32 two-week-old pigs obtained fr om 3 farms, but with similar Landrace x Yorkshire genetics for trial 1 of each experiment; 16 pigs for trial 2 of the A pleuropneumoniae exp eriment; and 14 pigs for trial 2 of the PRRSV experiment. Procedure-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, pi gs were seronegative to A pleuropneumoniae serotypes 1 and 5 on the ba sis of results of an ELISA, but had positive results on the A pleuropn eumoniae hemolysin (Apx1)-neutralization test. Pigs in trial 2 had neg ative results on both tests. Pigs of trial 1 of experiment 2 were inoc ulated with a PRRSV virulent field isolate (MN-1b), pigs of trial 2 we re 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 p leuropneumoniae infection 12 days after initiation of the experiment. In trial 1 of experiment 2, all inoculated pigs (8/8) seroconverted, b ut only 2 of 8 contact-exposed pigs seroconverted. Aerosol-exposed pig s did not seroconvert nor was virus isolated. In trial 2, all inoculat ed and contact-exposed pigs seroconverted. All aerosol-exposed pigs se roconverted after 21 days, and virus was isolated at 16 days. Conclusi ons-A pleuropneumoniae was transmitted by air at a distance of 1 m whe n pigs were fully susceptible to the organism. Transmission of PRRSV a ppeared to be strain dependent; when reference strain VR-2332 was used , airborne transmission of PRRSV was documented.