The largest animal illness outbreak in American history has been caused by the avian influenza H5N1 wave, which has so far infected 76 countries, sparked national emergencies, and killed millions of wild birds and domestic poultry. The International Organization for Animal Health estimates that more than 140 million chickens have either perished from the virus or have been killed to stop its spread. Wild bird die-offs, however more difficult to count, have proved disastrous.
The momentum must be stopped by something. Industry experts are privately discussing taking a move they have long resisted: immunizing commercial chickens, laying hens, turkeys, and ducks against the flu in the US, where losses are close to 60 million.
That doesn’t sound contentious at all; after all, influenza vaccinations for people are commonplace, and poultry already gets a number of jabs in their first few days of life. Yet, only a select few nations regularly immunize chickens against avian influenza. The introduction of vaccination might result in trade restrictions that would destroy the substantial US export market, pit different chicken industry sectors against one another, and possibly raise consumer concerns about the safety of their food.
Thus, the industry formally rejects what would be a harsh measure. Nonetheless, no one would publicly admit it, but scientists at poultry firms said they don’t see any other options. Researchers that collaborate with the US sector claim that while there may not be much of an option but to start the vaccine process, the US cannot do so on its own.
According to Karen Burns Grogan, a veterinarian and clinical associate professor at the University of Georgia’s Poultry Diagnostic and Research Center, vaccination is a topic that is being considered on a worldwide basis since it would be a decision that would affect everyone. (Georgia produces around 1.3 billion broilers, or meat chickens, annually, more than any other state.) A decision would need to be made by everyone, including the US federal government, the International Organization for Animal Health, and trading partners.
But there’s no certainty that a choice will be made. After a significant outbreak in 2015, the federal government ordered limited supplies of bird vaccines against H5N1 flu, but they might not be able to stop the current strain from spreading. These cannot be used, according to the US Department of Agriculture. And because those doses would probably be administered by hand, increasing the supply sufficiently to protect billions of birds would need both a huge labor force and a massive industrial endeavor.
The conversation needs to be had soon. Although the virus they received was different from the one presently ravaging through birds, and there was no indication the sickness transmitted from them to others, the H5N1 flu recently killed an 11-year-old girl in Cambodia and sickened her father. It is quickly adapting to mammals, most recently killing minks raised in Spain and sea lions off the coast of Peru.
In contrast to its previous pattern, in which wild birds carried the virus but were unaffected by it, H5N1 flu is also causing the death of an uncountable but undoubtedly an enormous number of wild birds. According to naturalist Peter Marra, who also serves as the head of Georgetown University’s Earth Commons Center, the effect on wild bird populations is unparalleled. Several gannets and other species have completely disappeared. And this is true not just of the United States but also of the rest of the Western Hemisphere, including, we presume, Africa.
Moreover, outbreaks in poultry are growing despite the industry’s efforts to tighten its biosecurity procedures. These epidemics result in a great deal of animal suffering: The rapidly spreading illness is so frightening that a well-known expert once dubbed chicken Ebola.
However, a portion of American veterinarians argues that it is inhumane to kill hens by turning off the air, causing them to suffer heat stroke, in order to avoid the spread of disease. The impact on the food supply follows. Last year, flock losses among laying hens alone reduced egg availability by 29% while tripling costs.
The destruction among those hens gives away difficulties in immunization. Depending on what it is used for, every variety of commercial poultry is permitted to live to a different age: Layers and broiler breeders (the parents of meat chickens) are allowed to survive for a year or longer since hens can’t start producing eggs until they’re approximately 26 weeks old, but broilers reach their full size in six to seven weeks and turkeys take around six months to reach market weight.
The fact that the longer-lived breeds—layers, and turkeys—seem to account for more flu-related deaths is peculiar but noteworthy. (It may in part be a result of layer farms housing so many animals on each property that the virus’s introduction kills a lot more birds.) It follows that the poultry and egg industries would gain the most from vaccinations.
But the majority of the US’s poultry exports are neither eggs nor turkeys. Meat is what broilers cook, along with extras like feet that Americans don’t prefer to eat. According to the USDA, broiler meat exports brought in more than $5 billion in 2021.
The argument that the immunological response to vaccination and influenza illness is so similar that healthy birds cannot be separated from carriers is one that many foreign nations that import US chicken have long used to reject meat from vaccinated broilers. In other words, the US chicken industry that needs a vaccination the least would stand to lose the most financially from employing one.
That calculation might be altered by the severity of H5N1’s global attack. An international conference held in Paris last fall looked at lifting impractical restrictions on the use of the avian flu vaccination. The European Union published new laws in November that, subject to certain requirements, allow the vaccination of chickens. Countries in Central and South America, where H5N1 has only recently arrived, have indicated they will start immunizing poultry.
The USDA also approved a five-year study that will look for new avian flu vaccinations, figure out how to demonstrate that they work, and map out whether using such doses causes the flu virus to mutate in ways that vaccines wouldn’t be able to protect against.
Years ago, a section of the flu research community maintained that it was easy to tell diseased birds from vaccinated ones. The DIVA method (for identifying infected from vaccinated animals) involves changing one protein in the circulating strain that is used to produce the vaccine in order to provide a molecular marker.
When tested, vaccinated chickens show antibodies to the substitute strain rather than the wild type, proving that their immunity is a result of the vaccine and that they are therefore safe for trade. The method was applied twice in Italy, in 2000 and 2001, to stop poultry outbreaks brought on by the H7N1 and H7N3 influenza strains.
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According to Ilaria Capua, a virologist and senior fellow for global health at Johns Hopkins SAIS Europe in Bologna, other nations have always claimed that the costs associated with vaccination—which include the vaccine itself as well as the testing and potential restrictions on movement—were not worth it. Capua proposed the use of the system in Italy while working at the Istituto Zooprofilattico Sperimentale delle Venezie. But if you implement a mechanism that notifies you that a flock is immunized and has not been exposed to the virus, the trade barriers can be eliminated.
Usage of the DIVA system was discontinued in Italy due to the multiyear H7 strain wave fading (albeit not before it claimed the life of a Dutch veterinarian) and the lack of resources in other countries that were at danger at the time to develop a system akin to it. Due to the global spread of the H5N1 flu, the situation has changed. The number of poultry and wild bird species it has been able to infect is a sign that the virus is spreading to a greater number of hosts where it can evolve into more severe forms as well as an indicator of the amount of harm it is causing.
According to experts, this reality makes the need for poultry immunization more pressing. It has long been understood that flu can transfer from wild to domesticated birds via ponds, droppings, or tiny birds that can fit between fan covers. Yet, it’s also likely that during certain times, the flu spreads to wild birds. And while it would be impossible to organize the logistics of immunizing wild birds, we can easily immunize domesticated birds.
