Avian flu: Time to rethink on-farm surveillance?

— OPINION —

The spread of bird flu to dairy cows, along with the discovery of viral fragments in 20 percent of retail milk samples, has turned an outbreak that long vexed poultry farmers into a source of stress for consumers. The situation is fraught with uncertainty as researchers’ understanding of the virus evolves, along with the virus itself. On one point, however, the evidence is in: the U.S. needs better surveillance of pathogens on large livestock farms. 

As of this writing, the Centers for Disease Control and Prevention has reported confirmed cases of the highly pathogenic avian influenza virus A(H5N1) in domestic livestock in nine states. The virus is “highly pathogenic” to birds, and to many other animals, including seals, but for now, CDC says the risk of infection to the general public “remains low.”

Epidemiologists have long raised concerns that a “bird flu” variant may adapt to infect humans and cause another pandemic. When an H5N1 bird flu virus was first detected in 1996, it went on to infect nearly a thousand people with over a 50 percent death rate. In 2009, an avian influenza virus that jumped to pigs—swine flu—caused an estimated 12,469 deaths in the United States. The A(H5N1) virus has yet to result in a confirmed human death or serious illness. However, its lethality in wild life populations, and its widespread transmission between many species of mammals, including dairy cows, have raised concerns. 

Exposure to infected dairy cows presumably caused the most recently confirmed case of human illness, reported by Texas officials on April 1. An earlier 2022 case, in Colorado,  involved exposure to infected poultry. Both of those cases were reportedly mild.  But influenza viruses are notorious for shapeshifting. The risk of A(H5N1) morphing into a pathogen that spreads easily between humans, with more serious health consequences, justifies a vigorous surveillance program to track where the virus is cropping up, how it is changing, and under what conditions it is spreading. 

Unfortunately, we are missing a critical component of that surveillance — on the farm. Authorities with USDA’s Animal and Plant Health Inspection Service (APHIS) have issued an order requiring mandatory testing of A(H5N1) in dairy cattle that cross state lines. But we need a broader sampling program. In addition to insights into all of the cows that stay in their home states, federal authorities should be pulling samples from other species, particularly pigs, which many experts see as a critical bridge between flu viruses that kill birds and people.  

USDA has authority to require testing, at least for animal diseases. Federal statutes give the agency the power to “carry out operations and measures to detect, control, or eradicate any pest or disease of livestock (including the drawing of blood and diagnostic testing of animals), including animals at a slaughterhouse, stockyard, or other point of concentration.” 7 U.S.C.A. § 8308. Concentrated hog and other concentrated animal feeding operations (CAFOs), i.e. the source of the vast majority of all animal livestock and animal products consumed in the United States, presumably fall under “other points of concentration.” So USDA would seem to be on firm legal footing were it to implement an A(H5N1) testing requirement for hog farms. The law requires USDA to compensate farmers for testing costs, but if costs are preventing USDA from conducting critical surveillance to prevent the next pandemic, it should ask Congress for more money. 

The pork industry may protest that A(H5N1) is not a disease that affects hogs, and that testing hogs for the virus would really amount to a public health surveillance program. To the extent this characterization is correct, it poses a problem, because the federal government lacks authority to require, or itself conduct, on-farm public health surveillance. Why are federal officials empowered to go on-farm to detect animal diseases, but not human diseases? Congress needs to address this absurd discrepancy. 

Bird flu aside, public health officials’ lack of authority to conduct basic epidemiological surveillance on farms affects food safety.  Recent investigations in which the animal livestock industry refused to cooperate with federal requests for microbiological sampling include a Salmonella outbreak linked to pork, and an outbreak of E. coli O157:H7 infections linked to romaine lettuce suspected to be contaminated with manure from an adjacent feedlot that hosted over 100,000 cattle. Whole genome sequencing of samples from the hog and cattle operations implicated in these outbreaks, and countless others, may have yielded important clues about the outbreaks’ origins, and how to avoid similar food safety breakdowns. But under the current oversight regime, livestock producers simply do not have an incentive to submit to sampling requests. 

Fortunately, there are efforts underway to fix this problem. My organization, Consumer Federation of America, has joined other consumer advocates in supporting the Expanded Food Safety Investigation Act. The bill, now endorsed by 10 members of Congress across both houses, would give the U.S. Food and Drug Administration the authority to conduct microbiological sampling on CAFOs for the purposes of investigating a foodborne illness outbreak or any other public health need. 

So far, the industry has not had to grapple seriously with requests to explain its opposition to seemingly common-sense measures like the Act. But as new pathogens like the A(H5N1) virus emerge, demand for reform will grow. Rather than reflexively obstructing efforts to increase transparency, livestock industry leaders should join in the conversation and help guide the development of effective pathogen surveillance protocols on-farm.

In the meantime, consumers can protect themselves from the A(H5N1) virus in food by avoiding raw milk, and practicing the “four core” food safety handling practices for meat and poultry, including eggs. For workers, CDC has issued guidelines on the use of PPE.

With luck, the A(H5N1) virus will remain innocuous to humans and soon leave the public eye. However, we should not wait for a crisis to begin establishing critical public health infrastructure. That infrastructure includes policies to effectively conduct on-farm surveillance of human illness causing pathogens.

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