Submitted to: American Association of Swine Practitioners Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 11, 2000
Publication Date: N/A
Technical Abstract: Field reports have suggested that transmission of porcine reproductive and respiratory syndrome virus (PRRSV) can occur by direct contact (pig-to-pig and virus-contaminated semen) and it may occur by indirect contact (fomites, biological or mechanical vectors, and aerosol transmission). Experimental studies have demonstrated direct transmission from infected to onaive swine by way of pig contact and insemination of virus-contaminated semen, while results from aerosol transmission studies (the only indirect transmission studies that have been reported) have been equivocal. During a field investigation of maternal reproductive failure epizootics in north-central Iowa swine farms, we received samples from 7 farms from which PRRSV was isolated. The farms were located relatively close to each other and reported clinical signs at about the same time. The viral isolates had the same RFLP patterns, and, based on genetic analysis, the isolates from 6 6of the 7 farms were 99.5 - 100 % identical at the amino acid level; the 7t farm's viral isolates had about 96.5 - 98% homology. Based on interviews with the producers and their veterinarian, there appeared to be no common link between these farms suggesting area spread of virus among these farms occurred, possibly by aerosol transmission. These findings peaked our interest into the possibility that aerosol transmission could occur and this study was initiated to demonstrate aerosol transmission of a PRRSV field isolate that may have been transmitted among farms by aerosolization. PRRSV was transmitted by aerosol transmission in 1 of the first 2 trials. Additional PRRSV trials are underway along with dual infection trials (PRRSV and pseudorabies virus) designed to evaluate if dual respiratory pathogen infections have a synergistic effect on aerosol transmission.