By Marcelo Lang, DVM*
Farsight Consulting & Marketing Services, LLC
Over the past 29 years, the highly pathogenic avian influenza (HPAI) virus known by its molecular fingerprint as H5N1 has gone from a localized menace found in domestic waterfowl in China and Hong Kong to a global scourge that threatens to wipe out large parts of the poultry industry. It is significantly reducing the availability of poultry meat and eggs while increasing the prices for millions of consumers.
Since 2021, the H5N1 virus has adapted to infect several mammalian animals, from sea lions to dogs and cats, and very recently, in the US, to dairy cattle. More significantly from a public health standpoint, this virus is also a potentially zoonotic agent, meaning that it may adapt to humans. A recent scientific study concluded that a single nucleotide mutation in a specific viral genome region could allow it to transmit from human to human. Depending on if and how the virus mutates, it could have the potential to start a global pandemic, possibly even more devastating than the recent one caused by COVID-19.
Besides the recent adaptation to mammals, the H5N1 virus is widely established in wild waterfowl and other migratory birds, which spread their viral load around the world. While it’s difficult to give a single, precise percentage due to variations in location and time, studies indicate that during outbreaks a significant portion of wild waterfowl populations can be infected with the H5N1 virus, with some studies finding infection rates in the range of 10% to 60% among sampled waterfowl, particularly during migration periods when birds congregate in large numbers. Not all infected birds will show symptoms, however, and the actual percentage of infected birds in the wild is likely higher than what is detected through sampling.
Should we start vaccinating poultry?
With all these factors, the question is: Why don’t we start vaccinating poultry flocks against this disease in the US and other important poultry-producing countries in the world?
The technology exists, and many different types of avian influenza vaccines have already been used to curb outbreaks in other countries with relative success. What’s stopping the US poultry industry from using vaccines to help prevent a disease costing producers millions of dollars?
Behind this seemingly simple question, there are huge technical, economic and political complications that make a straightforward answer virtually impossible.
The US poultry industry’s dilemma was laid out plainly in a recent letter that members of the Congressional Chicken Caucus — a loose congregation of Congress members from both parties — recently wrote to the new US Agriculture Secretary, Brooke Rollins. The group asserted that “vaccination in any poultry sector — egg layers, turkeys, broilers or ducks — will jeopardize the entire export market for all US poultry products.”
They added, “The problem is that most US trading partners do not recognize countries that vaccinate as ‘free of HPAI’ due to concerns that vaccines can mask the presence of the virus,” regardless of product categories or geographic separation of the vaccinated and unvaccinated flocks.
For example: They raised the possibility that vaccinating egg layers in Michigan could make an unvaccinated broiler chicken in Mississippi unacceptable to poultry importers. According to the Congressional Chicken Caucus, what is at stake in the HPAI vaccine discussion is the potential $10 billion-plus annual loss to the US economy and American broiler farmers, who so far have been the least affected by the H5N1 virus.
Political pressure
One other pushback on vaccination emerged earlier this week, but it has nothing to do with economics.
Speaking on Fox News, the new US Health and Human Services Secretary, Robert F. Kennedy, Jr. — widely known for his opposition to vaccines in humans — expressed concern that HPAI vaccines for poultry may not provide sterilizing immunity (100% protection) and thereby open the door to new mutations of the virus.
As anyone involved in animal health knows, vaccines rarely if ever reach that level of efficacy. Nevertheless, properly managed vaccines are valuable tools for fighting diseases and, in some cases, reducing the need to use antibiotics to treat primary and secondary infections. If vaccine efficacy and their role in possible HPAI mutations are a valid concern, let us hope the government’s decisions on vaccination will be based on sound science, not preconceived opinions or biases.
The French connection
The broiler sector of the US poultry industry has made sound arguments against vaccinating for HPAI, but the pros and cons nevertheless warrant debate and discussion as we look at the big picture and past experience. Recent history dealing with France’s 2023 decision to vaccinate — and more significantly, how USDA’s position on this matter evolved — is worth noting here.
Until recently, all countries that have used vaccines to fight avian influenza were importers of poultry products. The one exception was France, a significant exporter of poultry meat, which started vaccinating commercial duck flocks in 2023 using inactivated and mRNA vaccines.
The HPAI vaccination protocol in France mandates that all farms with more than 250 ducks vaccinate the birds. The campaign also includes a strict surveillance system. Furthermore, the vaccines must be used as part of a strategy called DIVA — differentiating infected from vaccinated animals — so authorities can distinguish between flocks vaccinated for HPAI from those that contracted it naturally.
Interestingly, the US and Canada initially banned but later reduced restrictions against importing French poultry products. In justifying its decision to ease the restrictions, officials with USDA’s Animal and Plant Health Inspection Service (APHIS) said it evaluated the HPAI vaccination practices in France to determine if HPAI vaccination significantly impacted the likelihood that unmitigated poultry commodities capable of transmitting the HPAI virus could enter the US from France, other members of the European Poultry Trade Region or European Free Trade Association countries.
“Consistent with science-based trading principles, the evaluation focused on France’s HPAI vaccination plan and regulatory oversight, their ability to ensure only target birds are vaccinated, the traceability of their poultry commodities, and their post-vaccination surveillance methods,” APHIS reported at the time.
APHIS concluded the HPAI vaccination initiatives in France “had not significantly impacted the likelihood of HPAI virus entering the US.”
Following this experience, I’m compelled to ask whether this same cautious, science-based rationale for allowing some imports of vaccinated poultry could be reversed and used to support HPAI vaccination in the US today. It’s clear that both vaccinating and not vaccinating bring both risks and rewards for the industry. Which path we take depends largely on how the US poultry industry adapts to the rapidly evolving and spreading HPAI threat.
Technical pros and cons
Now, let’s turn to the technical side of the HPAI vaccination question.
Proponents of the vaccines argue that vaccinated birds are likely to have increased resistance to avian influenza virus infection and decreased replication of the virus in their respiratory and gastrointestinal tracts. They also say vaccination leads to reduced viral shedding, resulting in less environmental contamination and reduced spread among and between premises. Furthermore, by reducing the spread of the virus, vaccination also can help maintain poultry production and reduce the economic impact of avian influenza outbreaks.
Opponents of vaccination counter that, in addition to the huge losses in export revenues, vaccinated birds may still become infected and serve as a source of the virus for spread to other flocks, potentially leading to asymptomatic spread. They say there are several issues to consider, including production capabilities, logistical considerations, regulatory and trade implications, and legal licensing requirements. Opponents also note that vaccination does not prevent HPAI infection entirely, and in some cases, vaccinated birds may still need to be culled if they become infected.
Navigating choppy waters
When I reflect on all these complicated and controversial arguments, I can’t help but wonder: How can the US government, the poultry industry, its allied industries and all other stakeholders skillfully navigate this delicate situation without incurring major economic losses?
Currently, it’s hard to imagine USDA mandating and facilitating a national vaccination campaign that targets some types of poultry farms while exempting or prohibiting the practice on others. Egg and turkey producers, which have suffered the most economic losses from HPAI, would likely embrace mandatory vaccinations while producers of broiler meat for export markets would suffer the consequences. On the other hand, if the US chooses not to vaccinate at all, the industry likely will continue to witness the demise of the egg and turkey sectors while broiler integrators preserve their export business, even at the cost of suffering sporadic losses from the highly infectious viral disease.
Finding a workable and equitable solution may require multiple steps, such as further increasing biosecurity and surveillance, continuing to stamp out affected flocks and implementing targeted vaccination in areas with greatest risk, based on the surveillance of wild birds and domestic animals. Most importantly, the US must lead a global discussion on how to control this transborder disease, creating a new consensus that vaccination status against HPAI should not be used as a trade barrier.
This last point may sound overly optimistic. However, when you consider that the US poultry industry is the second largest exporter in the world behind Brazil, where would buyers of US poultry meat source the same volume and quality if they shun US imports due to HPAI vaccination?
Brazil is, of course, one option. No HPAI virus has ever been isolated from Brazilian commercial flocks (in 2023, H5N1 virus was isolated from a few dead migratory birds and backyard flocks in Brazil). Nevertheless, the local industry is very worried that eventually the virus will find its way into commercial flocks, causing severe losses there. Then what?
It’s time for us to recognize that HPAI has reached all continents and almost all significant poultry-producing countries. It’s not going away. The US still has extensive reserves of scientific leadership and goodwill with its trading partners to lead the way on this important, multilateral decision. The question is, how long can the US wait before the toll of HPAI becomes too high and/or sweeping government cutbacks compromise the US response to managing this disease? The time for global consensus is now.
*Dr. Lang is an industry trendwatcher with more than 35 years’ experience in poultry. After working for several animal health and nutrition companies, he opened his consultancy, Farsight Consulting & Marketing Services.
Editor’s note: The opinions and/or recommendations presented in this article belong to the author and are not necessarily shared by Modern Poultry.
