CNN
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The United States is facing what some experts call “a new era for bird flu.”
Since January 2022, the country has been battling the largest outbreak to date of highly pathogenic avian influenza in wildlife. The virus is a great threat commercial and backyard flocks, and has begun to appear in hundreds of mammalsincluding a handful of domestic cats.
The risk to humans is low; There has only been one human case of this virus in the US since the outbreak began, according to the US Centers for Disease Control and Prevention, and nine cases worldwide, mostly among people. who work with birds. He Centers for Disease Control and Prevention He says, there is ongoing trials of vaccines that could be used to protect humans should the virus change and become a greater threat.
Separately, the US Department of Agriculture, the US National Center for Poultry Research and laboratories at a handful of US universities have been experimenting with candidate vaccines for use in birds.
The USDA Agricultural Research Service began trials of four candidate vaccines for animals in April and hopes to have initial data on a single-dose vaccine available this month. A two-dose vaccine challenge study, in which animals are challenged with the virus to see how well the vaccine works, should produce results in June.
If the animal vaccines appear to be protective, the USDA’s next step would be to work with the manufacturers to determine if it would be feasible to use them.
One manufacturer, Zoetis, announced on April 5 the development of a vaccine targeting the currently circulating virus strains. The company says it would take around a year to get to the distribution stage in the US.
Vaccines are already available in other countries, including Porcelain, Egypt, Indonesia, Italy, Mexico and Vietnam, and some nations are vaccinating their commercial herds.
However, in the United States, not all poultry experts are ready to use a vaccine, even if it is available, at least not yet. Instead, their focus remains on eradicating the virus.
As of April 26, the CDC says, almost 58.8 million poultry have been affected by bird flu since January 2022. The virus has been detected in at least 6,737 wild birds, and the number is likely to be much higher. There have been outbreaks in poultry in 47 states.
Although this is the worst outbreak on record, enhanced biosecurity measures have greatly reduced the number of cases in the commercial sector, according to the USDA. When the outbreak began in early 2022, there were 51 detections among commercial birds. In March 2023, there were only seven.
The USDA says close surveillance work between its Animal and Plant Health Inspection Service (APHIS) and state and industry partners led to case reductions.
In general, there are two ways to deal with this type of highly infectious disease in birds, according to Rodrigo Gallardo, professor of poultry medicine and specialist in avian virology at the University of California, Davis.
“One of them is through the vaccination action. And then the other one is through eradication,” she said.
In the United States, the latter is the focus for now, Gallardo said.
If farmers detect even a single case in a flock, they will cull the birds immediately.
“The virus continues to replicate and amplify if the birds are alive, so the only way to stop replication and limit the spread is through depopulation,” Gallardo said.
Tom Super, senior vice president of communications for the National Chicken CouncilThe National Trade Association for the US Broiler Industry said in an email to CNN that while it supports ongoing discussions of a vaccination program, “we currently support APHIS’s eradication policy and believe that in Right now this is the best approach in removing [bird flu] In the USA”
He US Poultry and Egg Association He said it is “certainly a matter of discussion,” but the organization does not have a position on implementing a vaccination program.
A vaccination program comes with several complications, Gallardo said. Vaccinated birds would be protected, but with this highly infectious disease, they could still transmit some virus that could infect unprotected birds.
“So vaccination, in that case, creates amplification if it’s not done right,” Gallardo said.
Furthermore, it is difficult to detect the disease in vaccinated birds. Birds that are vaccinated don’t always show signs if they are sick, so it would be hard to know which birds to keep separate from others. The tests also have difficulty differentiating between antibodies generated by vaccination and antibodies from an infection.
“If you can’t diagnose it, it could spread more than it would if you could diagnose and eradicate it,” Gallardo said.
Countries that have chosen the vaccination route see more endemic strains develop, meaning the virus is never fully eliminated.
“This is a highly variable virus, and if you don’t update the vaccine you’re giving to meet the change in the virus, then you won’t be able to fully protect the birds. Partial protection means more birds will spread the virus,” Gallardo said.
A highly pathogenic avian influenza vaccine has never been used. In the USA, according to the USDA. The agency created a vaccine after an outbreak in 2014 and 2015, but that involved a different strain, so it wouldn’t work on the latest version of the virus.
The logistics of a vaccine like this are difficult, said Dr. Yuko Sato, an associate professor at the Iowa State University College of Veterinary Medicine.
“You have to make sure that the new vaccine protects against this current virus and hope that it doesn’t mutate or change so that the vaccine continues to provide protection,” Sato said.
“The vaccine is not a panacea. This is not going to prevent infection of the birds, so in order to have an exit strategy as a country, you would have to make sure that if you vaccinate, if you still have positive birds, you have to be able to make sure that you could kill off the virus. Otherwise, we will never seek to eradicate the virus from the United States.”
Another concern: Birds are big business in the United States.
The United States has the largest poultry industry in the world, with 294,000 poultry farms. The size of the market for chicken and turkey meat production alone by 2023 is projected to generate $57.8 billion, according to the market analysis firm. ibisworld.
Bird flu has hurt business in the US, but it could do so in a bigger way if the nation vaccinates poultry, according to the National Chicken Council.
“The National Chicken Council does not support the use of a vaccine for [bird flu] for a variety of reasons, the main one being trade. Most countries, including the US, do not recognize countries that vaccinate as free of [bird flu] due to concerns that vaccines may mask the presence of the disease. Therefore, they do not accept exports from countries that do vaccinate, ”Super wrote in his email.
The US broiler industry is the second largest exporter of chicken in the world. Exports around 18% of chicken meat produced in the United States, valued at more than $5 billion annually.
“If we start vaccinating for [bird flu] In the US, the broiler industry will lose our ability to export, which will have a significant impact on the industry, while costing the US economy billions and billions of dollars. every year,” Super said.
With the way the disease is spreading, scientists would probably have to vaccinate wildlife as well, which is next to impossible.
Of the birds affected in this outbreak, about 76% are commercial layers, 17% are turkeys and only 5% are broilers, the chickens used for meat, Super said. The rest of the cases have been among ducks, backyard chickens, and game birds.
“So the US poultry industry that needs a vaccine the least would be taking the most risk by using one,” he said.
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