US government tests bird flu vaccine for birds, but ending historic epidemic won’t be so easy

CNN
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The United States is facing what some experts are calling a “new era of bird flu.”

Since January 2022, the country has battled the largest-ever outbreak of highly pathogenic avian influenza in wildlife.the virus is big threat in commercial and backyard flocks, and it began to appear in hundreds of mammalsincluding a handful pet cat.

Risk to humans is low. According to the U.S. Centers for Disease Control and Prevention, he’s the only human case of the virus in the United States and nine worldwide since the outbreak began, mostly among people who handle birds. doing.of CDC say there is under trial of a vaccine that could be used to protect humans if the virus mutated and became more threatening.

Separately, laboratories at the US Department of Agriculture, the US Poultry Research Center, and several US universities are testing vaccine candidates for use in birds.

USDA’s Agricultural Research Service four vaccine candidates Initial data for a single-dose vaccine in animals are expected to be available this month, in April. A two-dose vaccination trial, in which animals are exposed to the virus to determine the effectiveness of the vaccine, should yield results. June results.

If animal vaccines appear to be protective, USDA’s next step is to work with manufacturers to consider whether their use is feasible.

One manufacturer, Zoetis, Announced on April 5th Development of vaccines against currently circulating virus strains. According to the company, it will take about a year to reach the distribution stage in the United States.

A vaccine is already available in other countries. include China, Egypt, Indonesia, Italy, Mexico Vietnam, and in some countries, vaccinate commercial flocks.

But in the US, even if a vaccine were to become available, not all poultry professionals would be ready to use it – at least not yet. Instead, their focus would be on eradicating the virus. Staying.

As of April 26, According to the CDCNearly 58.8 million poultry have been affected by avian influenza since January 2022, according to the WHO. The virus has been detected in at least 6,737 wild birds, and the number could be much higher. 47 states had poultry outbreaks.

This is the worst outbreak in history, but improved biosecurity measures have significantly 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 poultry. In March 2023 he was only seven.

According to the USDA, close surveillance work between the Animal and Plant Health Inspection Service (APHIS) and state and industry partners has reduced the number of cases.

According to Rodrigo Gallardo, professor of poultry medicine and expert in avian virology, there are generally two ways to combat this highly contagious disease in poultry. University of California, Davis.

“One of them is from vaccination. And the other is from eradication,” he said.

In the US, the latter is the current approach, Gallardo said.

Farmers kill birds as soon as they detect a single infection in their flock.

“As long as the bird is alive, the virus will continue to replicate and multiply, so the only way to stop replication and limit spread is to reduce the population,” Gallardo said.

said Tom Super, senior vice president of communications at National Chicken Councilthe National Trade Association of the U.S. Broiler Poultry Industry, in an email to CNN, said in an email to CNN that it supports ongoing discussions about a vaccination program, but that it “currently supports an eradication policy for APHIS and that at this time this I believe it is the best approach. Eliminate [bird flu] in the United States”

of American Poultry Egg Association He said it was “certainly up for debate,” but the organization has no position on the implementation of vaccination programs.

According to Gallardo, the vaccination program comes with some complications. Vaccinated birds are protected, but with this highly contagious disease, they can shed virus that can infect unprotected birds.

“In that case, vaccination causes amplification if not done correctly,” Gallardo said.

Additionally, it is difficult to detect disease in vaccinated birds. Vaccinated birds do not always show signs if they are sick, so it is difficult to determine which birds should be kept separate from others. I’m having a hard time telling the difference between the antibodies produced by the infection and those produced by the infection.

“If you can’t diagnose it, it can spread more than if you can diagnose and eradicate it,” said Gallardo.

We find that more endemic strains occur in countries that have chosen vaccination routes. In other words, viruses are never actually completely wiped out.

“This is a highly variable virus, and without updating the vaccines we apply to respond to changes in the virus, we will not be able to fully protect the birds. It means spreading the virus,” Gallardo said.

Vaccines have never been used against highly pathogenic avian influenza in the United States, According to the U.S. Department of AgricultureOfficials created a vaccine after the 2014 and 2015 outbreaks, but it contained a different strain, so it didn’t work with the latest version of the virus.

The logistics of such a vaccine are difficult, said Dr. Yuko Sato, an associate professor at the Iowa State University School of Veterinary Medicine.

“We need to make sure that new vaccines protect against this current virus, and hope that they don’t mutate or change so that they continue to protect,” Sato said.

“Vaccines are not a silver bullet. This is not going to keep birds from getting infected, so in order to have an exit strategy as a country, if you get vaccinated, if there are still positive birds, you can see them.” We need to make sure that we can eradicate the virus, otherwise we would never think of eradicating it from the United States.”

Another concern: Birds are big business in the US.

The United States has the world’s largest poultry industry, with 294,000 poultry farms. Chicken and turkey meat production alone is expected to be worth $57.8 billion in 2023, according to a market analytics firm. Ibis world.

Bird flu has hit U.S. businesses, but it could have a bigger impact if the nation vaccinates poultry, according to the National Chicken Council.

“The National Chicken Council does not endorse the use of vaccines. [bird flu] There are various reasons, but the main reason is trade. Most countries, including the United States, do not recognize vaccine-free countries as vaccine-free countries. [bird flu] Because of concerns that vaccines can mask the presence of the disease. Therefore, they do not accept exports from countries where they vaccinate,” Super wrote in his email.

The US broiler industry is the second largest poultry exporter in the world.Export about 18% Percentage of chicken produced in the United States worth more than $5 billion annually.

“Once you start vaccination, [bird flu] In the United States, the broiler industry will lose its ability to export and will have a major impact on the industry – costing the US economy billions of dollars each year.

The way the disease spreads, scientists would probably have to vaccinate wildlife, which is nearly impossible.

Of the birds affected by this outbreak, about 76% are commercial laying hens, 17% are turkeys, and only 5% are broilers (chickens used for food), Super said. The remaining cases are ducks, backyard chickens and game birds.

“Thus, the US poultry sector, which is least in need of vaccines, is at the highest risk of using them,” he said.