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Research Project: Control Strategies to Prevent and Respond to Diseases Outbreaks Caused by Avian Influenza Viruses

Location: Exotic & Emerging Avian Viral Diseases Research

Title: Testing of retail cheese, butter, ice cream and other dairy products for highly pathogenic avian influenza in the United States

Author
item Suarez, David
item GORAICHUK, IRYNA - Orise Fellow
item Killmaster, Lindsay
item Spackman, Erica
item CLAUSEN, NICOLE - Us Food & Drug Administration (FDA)
item COLONIUS, TRISTAN - Us Food & Drug Administration (FDA)
item LEONARD, CYNTHIA - Us Food & Drug Administration (FDA)
item METZ, MONICA - Us Food & Drug Administration (FDA)

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2024
Publication Date: 12/9/2024
Citation: Suarez, D.L., Goraichuk, I.V., Killmaster, L.F., Spackman, E., Clausen, N.J., Colonius, T.J., Leonard, C.L., Metz, M.L. 2024. Testing of retail cheese, butter, ice cream and other dairy products for highly pathogenic avian influenza in the United States. Journal of Food Protection. 88(2025:e100431. https://doi.org/10.1016/j.jfp.2024.100431.
DOI: https://doi.org/10.1016/j.jfp.2024.100431

Interpretive Summary: Highly pathogenic avian influenza (HPAI) is a serious and highly transmissible disease in poultry. The United States has been dealing with a H5N1 HPAI in poultry and wild birds since early 2022, and over 100 million have been affected by the outbreak. although HPAI is primarily a bird disease, recent spread of the virus to mammals has occurred including a major outbreak of infection in dairy cattle. Cows in milk production are getting a mastitis that is affecting the milk quality and quantity. Because of the virus infection in the mammary gland, there can be high levels of virus in the milk, which creates a potential of zoonotic infection. Pasteurization of milk has been shown to inactivate the virus. As part of ongoing project, retail dairy samples were tested for viral RNA by a PCR method. This test can detect the presence of viral RNA, but it can't determine if the virus is live and infectious. Further studies are needed to culture the virus. In a study that looked at fluid milk, cheese, ice cream and butter, 17% of the samples had viral RNA, but none of the samples had had live virus demonstrating these products were safe for the consumer. Continued research is needed to assure a safe dairy supply.

Technical Abstract: The recent outbreak of highly pathogenic avian influenza (HPAI) in dairy cows has created public health concerns about the potential of consumers being exposed to live virus from commercial dairy products. Previous studies support that pasteurization effectively inactivates avian influenza in milk and an earlier retail milk survey showed viral RNA, but no live virus could be detected in the dairy products tested. Because of the variety of products and processing methods in which milk is used, additional product testing was conducted to determine if HPAI virus RNA could be detected in retail dairy samples, and for positive qRT-PCR samples to be tested for presence of live virus. Revised protocols were developed to extract RNA from solid dairy products including cheese and butter. The solid dairy product was mechanically liquified with garnet and zirconium beads in a bead beater diluted 1 to 4 with BHI media. This pre-processing step was suitable in allowing efficient RNA extraction with standard methods. Trial studies were conducted with different cheese types with spiked in avian influenza virus to show that inoculation of the liquified cheese into embryonating chicken eggs was not toxic to the embryos and allowed virus replication. A total of 167 retail dairy samples, including a variety of cheeses, butter, ice cream, and fluid milk were collected as part of nationwide survey. A total of 17.4% (29/167) of the samples had detectable viral RNA by quantitative real-time RT-PCR targeting the matrix gene, but all samples were negative for live virus after testing by embryonating egg inoculation. The viral RNA was also evaluated by sequencing part of the hemagglutinin gene using a revised protocol optimized to deal with the fragmented viral RNA. The sequence analysis showed all viral RNA positive samples were highly similar to reported HPAI dairy isolates. Using the revised protocols, it was determined that HPAI viral RNA could be detected in a variety of dairy products, but existing pasteurizations methods effectively inactivate virus assuring consumer safety.