The objective of this study is to detect airborne influenza A virus from acutely infected pig populations in the field.
Two acutely infected pig populations raised under commercial conditions were identified through constant communication with local veterinarians. Upon diagnostic confirmation of influenza infection, a total of fifteen 30-minute air samples were collected inside and outside the barn using a cyclonic collector. Additionally, 15 oral fluid samples were collected from pigs inside the barn. If a population tested positive in the first visit, a second visit was scheduled seven days after the first visit and testing repeated. Air and oral fluid samples were tested for influenza RNA by RRT-PCR.4 Further diagnostics included virus isolation, titration, strain subtyping and sequencing.
In farm 1 (nursery), all air samples (inside and outside) tested positive for influenza A. Virus was isolated from 8 (7 inside and 1 outside) air samples. Virus was also isolated from 11 of 15 oral fluid samples. During the second farm visit, out of 15 air samples collected inside the barn, 6 were classified as suspect. Out of 15 air samples collected outside, 2 tested positive and 1 was classified as suspect. All 15 oral fluid samples tested positive. No virus was isolated from these samples. On farm 2, a wean-to-finish barn, with influenza clinical signs in the later stage of the disease, four (2 inside and 2 outside) air samples were classified as suspect. All 15 oral fluids tested positive for influenza A. No virus was isolated from these samples.
Our results confirm that acutely infected pig populations do generate airborne influenza A virus viable particles capable of being exhausted from pig barns and likely disseminated to other farms in the vicinity. Additionally, acutely infected populations can generate viable particles for at least a week after infection.
C.A. Corzo; M. Torremorell; S. Dee; M. Gramer; R. Morrison. Detection of influenza virus in aerosols from swine farms. 2011 Allen D. Leman Swine Conference.