The American poultry sector is awaiting a spring spike in detections of highly pathogenic avian influenza, leading industry and government officials to wonder if the disease has pivoted from an occasional concern to a permanent part of raising birds in the United States.
The current outbreak, which began in February 2022, is considered the worst and most costly animal disease outbreak in U.S. history. According to figures from USDA's Animal and Plant Health Inspection Service, HPAI has been confirmed in more than 791 flocks as of March 14, 2022, 321 of them commercial. In total, nearly 59 million birds in 47 states have died or were depopulated, with 90% of the infections occurring in the northern half of the United States, mostly in the central and Mississippi flyways.
The previous outbreak of HPAI, which began in late 2014 and ended in 2015, was the first U.S. outbreak in 30 years. During that period, 211 farms were affected; detections were reported in 15 states, but nearly 90% of the confirmations were on operations in Iowa and Minnesota. Transmissions during that outbreak were heavily farm-to-farm, and a total of 50 million birds died or were culled.
“Before the 2014-15 outbreak, there were few people still working who had experience with HPAI response and control. We were unprepared then,” said Carol Cardona, a professor in avian health at the University of Minnesota College of Veterinary Medicine.
“Many people today — state, federal, private sector — have experience with control and response, and there has been little farm-to-farm spread,” she added.
In the 2014-15 HPAI outbreak, only 21 backyard flocks were reported; the current outbreak has more than 20 times that number (470 confirmed detections). With improvements in biosecurity following the 2014-2015 outbreak, the current wave is increasingly being spread by wild birds.
Carol Cardona, University of Minnesota
Sarah Bevins, a biologist at APHIS’ National Wildlife Research Center, said the amount of virus in the landscape is “staggering.” The National Wildlife Research Center samples wild birds to provide an early warning system to the poultry industry and has been testing hunters’ birds for the past 15 years in partnership with the National Wildlife Refuge System. Out of the 30,000 birds tested in the current outbreak, 6,000 individuals, or 20%, and 100 species have tested positive for HPAI. In 2014-15, Bevins said fewer than 100 birds tested positive over the six-month outbreak.
“This outbreak is being spread by wild birds (mostly waterfowl). We cannot relax. We will soon see another spike,” said Jenny Lester Moffitt, USDA's undersecretary for Marketing and Regulatory Programs, which includes APHIS.
Bevins noted that because spring migration of wild birds typically occurs over a shorter period than fall migration, this spring’s spike of HPAI could start and end more quickly than the surge that occurred last fall.
Jeffrey Sullivan, a biologist at the U.S. Geological Survey's Eastern Ecological Science Center in Maryland, studies the virus in wild birds. While he expects a spike in HPAI cases this spring, he does not think it will be worse than what occurred last spring and likely not as bad as what occurred in the fall.
“The viral levels experienced by wild birds will likely be comparable,” Sullivan said. “In fall migration, there’s more viral spread and more naïve (young) birds become infected. In spring migration, there are fewer naïve birds and lower prevalence of the virus. Most birds are coming out of condensed wintering grounds with some level of immunity in spring.”
That said, spread will occur, and the industry will need to remain diligent because the viral load on the landscape is still very high. Sullivan cautions against complacency, even in counties that have yet to confirm an outbreak, “because there are a lot more infected wild birds in this outbreak than in 2014-15, it means there is much more virus on the landscape.”
“As birds start to migrate, understand that the virus is moving with them,” he added. “We need to be ready for that.”
While low-path avian influenza is endemic to the United States and has likely been in the country for thousands of years, the current strain of HPAI is thought to have originated in Africa and then moved through Asia and Europe, with one U.S. introduction occurring through Canada and another by way of Asia through the Pacific Flyway. Preventing transmission takes a concerted effort from producers, industry, and government, something Moffitt said will be a priority at the federal level.
“Prevention is key,” Moffitt said. “We continue to work with states as well as industry,” adding that USDA has deployed 800 employees to manage the response.
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With what appears to be evolving into an ever-present problem, poultry producers will need more tools in their arsenals to assess risk and prevent infections. Researchers at the USGS Eastern Ecological Science Center have developed transmission risk models for each week of the year for every county in the United States that poultry producers can use to access real-time risk information.
National Poultry Improvement Plan measures have provided a foundation for improved on-farm biosecurity, something Cardona said has contributed to farm-to-farm transfer dropping from 70% during the 2014-15 outbreak to 15% in the 2022-2023 outbreak. Companies with previous HPAI experiences have had fewer cases in the current outbreak than they did in 2014-15, she added.
Despite strict biosecurity practices, the protocols last spring were simply not rigorous enough to meet the sheer viral load in the environment, and unfortunately, Cardona said, “the level of biosecurity needed is not sustainable long-term and year-round due to the economic and labor issues facing the poultry industry.”
Industry leaders now must grapple with the intersection of biosecurity and finance in determining whether it would be cost-effective, for example, to build enclosed hallways between barns to reduce the number of entries from the outdoors. Consideration also needs to be given to the role of farm size in disease protection, the potential increased risk of outdoor composting, possible netting for backyard flocks, and if a Danish entry — a two- or three-step entry process designed to keep “dirty” and “clean” environments separate — and shower would be more protective or be so tedious that employees would start to skip steps.
“We used to think wild bird introductions into poultry facilities were rare events,” Cardona said, but this outbreak has proven otherwise.
USDA Undersecretary Jenny Lester Moffitt In Europe, a 2021-2022 HPAI outbreak is the continent’s largest ever, with 37 countries affected, 2,520 outbreaks, and nearly 3,900 detections reported in wild birds. All told, 50 million birds were culled, according to a December report by the European Food Safety Authority, European Center for Disease Prevention and Control, and the European Reference Laboratory for Avian Influenza.
In response, European governments have recommended improving biosecurity practices on poultry farms as well as increasing surveillance of wild birds and wild mammals, mammal farms, and humans who have been exposed to the virus.
“The evidence we have seen from Europe and the initial phases of introductions in the United States indicates endemicity is a real risk that needs to be taken seriously. We have not seen any evidence that it will die out in wild birds,” Sullivan said.
Bevins agrees. “Europe is a bit ahead of us in this outbreak. They have seen continental transmission and risk for two years. There is no reason to think we won’t see this continue.”
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