According to studies performed by the USDA Southeastern Poultry Research Laboratory in Athens, Georgia, the US H5N2 HPAI virus from 2015 had a median bird infectious dose that was 1,000 times higher than other HPAI viruses to date. As a result, carriers which would be able to ensure exposure to a large amount of virus were speculated to have played a role in virus spread.
Because 2015 HPAI sites were geographically separated, contaminated feed was suggested as a potential source of Avian Influenza Virus (AIV). The reason for this was that feed ingredients often have the potential to be exposed to migratory waterfowl (the source of the virus) and their droppings. It was possible that these ingredients could be contaminated during storage and remain contaminated through the transport and feed processing phases. Since ISU researchers led the investigation in Porcine Epidemic Diarrhea virus (PEDv) outbreak based on possible feed contamination, similar protocols and procedures could be applied to pursue the possibility of the HPAI outbreak via contaminated feed. Therefore, this study was designed to investigate if feedstuffs could be contaminated with AIV, and assess the virus’ stability in feed. The objective of this research are to identify if feedstuffs, such as corn, could be contaminated with AIV and serve as a potential carrier and source of exposure in commercial chicken or turkey operations; and assess how long AIV is viable in spiked feed under controlled situations.
Iowa State University lead scientists who worked on this project included Dr. Yuko Sato, assistant professor and extension poultry veterinarian for the state of Iowa; Dr. Phillip Gauger, associate professor, Department of Veterinary Diagnostic and Production Animal Medicine; Dr. Jianqiang Zhang, associate professor, Department of Veterinary Diagnostic and Production Animal Medicine; and Dr. Kyoung-Jin Yoon, professor in the Department of Veterinary Diagnostic and Production Animal Medicine. The research team also included Dr. Shahan Azeem, Dr. Baoqing Guo and ISU graduate students.
Commercial feed ingredients and complete layer mashes were collected for testing from three barns and four feed mills that had a previously confirmed positive HPAI diagnosis during the AI outbreak in 2015. These fourteen feed samples that were retrieved from infected barns, during the outbreak, tested positive for AIV using Polymerase Chain Reaction (PCR). However, virus isolation tests conducted on these samples were negative.
In addition, virus stability was assessed by using AIV-spiked feed to test the limit of detection of real-time reverse transcriptase PCR. Results showed a significant decline in virus recovery from spiked feed versus media, which served as ideal sample matrix for virus stability. No infectious virus was isolated. This demonstrates that exposure and contamination through feed is possible, but the stability and survivability of the virus in feed is low.
While adding to the body of knowledge about HPAI, the researchers feel that additional data on the survival length of the virus in feed would be beneficial to create better biosecurity guidelines in feed mills. In addition, a study on the impact of heat-chains and moisture levels in feed and its influence on the virus’ stability might also be of use to the industry.
Researchers concluded that the risk of infection through feed is low. However, managing and engaging in biosecurity is still essential for minimizing and eliminating potential pathways of contamination (such as egg shells used as ingredients in feed).