USDA drafts avian flu risk assessment for poultry and egg products

Lisa Schnirring Staff Writer
Dec 3, 2008 (CIDRAP News) – The US Department of Agriculture (USDA) yesterday released a draft of its risk assessment for contracting highly pathogenic avian influenza from eating poultry products, shell eggs, and egg products, a tool that could be used to reduce human illness from the virus and help target messages to consumers.

In releasing the risk-assessment draft, the USDA's Food Safety and Inspection Service (FSIS) said it was seeking public comments, which are due by Jan 31. The 186-page report and information on how to submit comments are available on the FSIS Web site (see link at end).

The draft risk assessment, which addresses highly pathogenic H5 and H7 subtypes, was developed by representatives from the FSIS, the USDA's Animal and Plant Health Inspection Service (APHIS), and the Food and Drug Administration, according to a press release yesterday from the USDA. The document went through an external peer review, along with reviews by other government agencies, the USDA said.

So far there has been no compelling evidence that links eating cooked poultry, eggs, or egg products to avian influenza infections in humans, the draft report said. Though the viruses aren't considered foodborne pathogens, researchers have isolated them from poultry muscle and egg interiors.

Two human illnesses may have been related to consuming infected duck blood products, though investigators could not rule out contact that the patients may have had with infected poultry. Despite this lack of evidence, human exposure to contaminated poultry and eggs is a concern for food safety experts, the report said.

Experts used available information on avian influenza viruses and mathematical modeling to make risk estimates for several poultry and egg scenarios, including production, processing, and consumer preparation. For example, the estimates assume that the viral load in a serving of poultry relates to the time between when the bird was infected and when it was slaughtered.

According to some of the scenarios, the draft risk assessment for poultry meat predicts that:

• Poultry flocks infected early in their growing period are 94% (chicken) and 98% (turkey) likely to be identified as positive for the virus before slaughter, processing, and sale.
• Infected flocks approaching market weight present a small risk of infected meat reaching commerce—6% (chicken) and 2% (turkey)—because there is less time for bird deaths to be detected on the farm.
• On-farm avian influenza testing offers the greatest chance of for curbing human infections; 95% can be prevented when birds are tested before slaughter.
• Relying on mortality observations on the farm and after transport isn't as practical, especially if birds are late in the grow-out period.
• Cooking poultry to the FSIS-recommended temperature of 165°F inactivates the virus, lowering the public health risk to a negligible level.
• Cross-contamination from infected poultry to uncooked foods could increase illness levels by 2.5%, and public health messages should emphasize this food-handling risk.

Regarding eggs and egg products, the USDA's risk assessment predicts that nearly all contaminated eggs from an infected flock could be removed from the distribution chain before they reach consumers. The report notes that thoroughly cooking eggs to 150°F inactivates the virus, but a few human illnesses are possible from undercooking contaminated eggs.

USDA research has shown that time and temperature recommendations for egg product processing can kill avian flu viruses. The report said dried egg white processing may not completely inactivate the pathogen, but the 7-day processing period may allow officials time to alert egg product processors before the drying is completed and the product is released to consumers. The USDA said its APHIS division is developing a separate illness risk assessment for egg products that are contaminated with avian influenza.

Once finalized, the avian flu illness assessment for poultry and eggs will give risk managers the decision-making tools they need to gauge the effectiveness of interventions that could reduce or prevent foodborne illnesses, the report said.

"This risk assessment can also be used to target risk communication messages, identify and prioritize research needs, and provide a framework for coordinating efforts with stakeholders," the USDA added.