Porcine reproductive and respiratory syndrome virus (PRRSV) and influenza A virus (IAV) are two major respiratory pathogens of pigs that can be transmitted through the air. In this study, we evaluated the detection of both PRRSV and influenza from air filters installed in sow farms located in medium to high pig density areas to evaluate whether used air filters could work as a means to monitor the regional spread for these viruses. Filters that had been installed for 6, 8, 11 and 14 months approximately were tested for the viruses. Out of the 136 filters installed, ten (1.5%) samples corresponding to seven (5%) filters from three farms tested positive for PRRSV. During the study, PRRS outbreaks were reported in four farms, however, only one PRRSV positive filter originated from farms that had PRRS outbreaks. It is important to note that this study was conducted prior to the emergence of PRRS 144 Lineage 1C. In contrast, 65 (47.8%) filters from all seven farms tested positive for influenza, with a total of 131 samples positive (19.3%). Partial sequencing of influenza was possible in some samples and an H3N2 human-like influenza virus was detected. Our study showed that detection of PRRSV and IAV in the air filters showed potential evidence of regional airborne transmission for these viruses, but additional investigations are needed to better understand the factors that contribute to airborne transmission of these viruses. Overall, the testing of used filters for regional surveillance should be further explored since it may be beneficial for some diseases under certain circumstances. For more information contact Montse Torremorell (torr0033@umn.edu).

Key Findings:

  • PRRSV was detected in a limited number of filters from sow farms located in medium to high pig density areas. However, overall incidence of infection in the farms was low which may be indicative of limited challenge to the farms.
  • In contrast, influenza was readily detected in used filters from sow farms, and a partial sequence indicative of an H3N2 human-like influenza virus was characterized from the filters.
  • Further investigations are needed in particular for seasons when PRRS and influenza activity is considered high.