Europe uses previously banned vaccines to fight bird flu

(ORDO NEWS) — In March, Christian Drouin, a French farmer from the Vendée, discovered that his chickens were dying from bird flu. He had to take drastic measures to destroy the livestock and prevent the spread of infection.

Usually veterinarians would come to the site to euthanize the birds with carbon dioxide. But veterinary teams have been overwhelmed with calls to cull herds infected with the virus, which now appears to be endemic in Europe.

Therefore, Drouin was advised to turn off the fans in the poultry houses. As temperatures rose, most of his 18,000 birds died of heatstroke within hours. The next day, neighbors helped him bury the carcasses. “After that, I lay in the dark, stunned by what I had done,” he told Agence France-Presse.

In an effort to eradicate the highly pathogenic strain of H5N1 avian influenza, France and other countries are culling a record number of poultry – more than 16 million birds since December 2021 in France alone.

Last year, the costs for these purposes exceeded 150 million euros. Now, faced with the desperation of farmers like Drouin, France, the Netherlands and other affected countries have resumed research on a solution long considered taboo: flock vaccination.

French and other EU ministers are discussing the idea, and Dutch scientists have already started testing chicken vaccines.

This week, scientists in southwestern France will begin vaccinating ducks with a newly developed vaccine. And in October, stakeholders will meet at the World Organization for Animal Health to discuss how to lower international barriers to shipping vaccinated poultry.

Currently, many countries are refusing such shipments because they are not sure that the virus is under control in countries with vaccinated birds.

Influenza experts fear that vaccination may not completely stop outbreaks, possibly raising the long-term risk that the avian virus will cross over to humans. In addition, the development and use of vaccines will be expensive.

For all these reasons, vaccination is the last resort, says avian pathologist Jean-Luc Guérin of the National Veterinary School of Toulouse. “We use this remedy only when we admit that we cannot control the infection in classical ways.”

The United States has not authorized the use of avian flu vaccines due to trade implications, hoping culling will stop the current outbreak.

The American poultry industry is taking a wait-and-see attitude. But in Europe, the devastation caused by the virus and the cost and logistics of culling millions of birds could change the calculations.

In places where a highly contagious new strain of bird flu has taken hold, vaccination “can really make a huge difference,” says Richard Webby, a virologist at St. Jude Children’s Research Hospital who studies influenza in birds and other animals. In the long term, the researchers say fighting H5N1 may require not only vaccines, but also a restructuring of Europe’s dense poultry industry.

Over the course of three decades, more and more new strains of bird flu have emerged in Asia. The current strain of H5N1 appeared in Europe in 2021. It was first detected in the US in January and continues to spread.

Some researchers are concerned that vaccination, if not done carefully, will allow H5N1 to persist and continue to mix with strains in wild birds, with the risk that it could evolve and spread to humans.

The risk to the European Union and the United States, while small, is likely the highest since H5N1 emerged 25 years ago, Webby says. “We really don’t want this virus lurking in poultry farms,” ​​adds Adele Talaat, an infectious disease expert at the University of Wisconsin-Madison.

The encouraging sign is that vaccines have reduced the impact of recent outbreaks, at least in China. In 2017, the country began mandatory vaccination of poultry against the H7N9 strain, which has been able to spread to humans.

Vaccination has reduced the prevalence of the virus in poultry and the number of human infections has dropped to zero. The achievement “could be replicated everywhere,” says virologist Hualang Chen of the Harbin Veterinary Research Institute, which developed the vaccines.

The campaign has also paid off for Chinese farmers who have resumed broiler chicken production, according to a cost-benefit analysis published in March in the journal Preventive Veterinary Medicine.

And the United States continues to accept Chinese poultry products, showing that trade barriers are not insurmountable. Vaccines also promote animal welfare by reducing the need for culling, adds Chen, who “strongly” recommends vaccinating birds against the H5 strain.

However, the strain of H5N1 now in Europe can be difficult to control with vaccines because it infects many animal species, including ducks, while H7N9 is a problem mainly in chickens, Webby says. In addition, economic factors may favor the culling of animals in sporadic outbreaks.

But vaccine trials are starting in stricken France. Two vaccines will be tested on ducks raised for foie gras. Bird flu-carrying ducks are an “absolute reservoir” because they can shed the virus for up to 15 days before symptoms appear, Guerin said. In the trials, birds will be vaccinated on farms and then exposed to the virus in the laboratory. The goal is to reduce the amount of circulating virus and thus protect other poultry species.

One of the vaccines, Volvac Best, is manufactured by Boehringer Ingelheim and is already being used in countries outside of Europe, including Mexico and Egypt, to immunize chickens against Newcastle disease and H5N1.

Ceva has created another vaccine, the first RNA vaccine tested in poultry, specifically for ducks. The results should be in by the end of the year, says Gilles Salvat, a veterinary health expert at the French Agency for Food, Environment and Occupational Health and Safety. If the vaccines prove effective in reducing levels of the virus, Salvat hopes they will be ready for sale by the end of 2023.

Once farmers have vaccinated their flocks, they will need to ensure that the virus does not circulate silently among birds that have been missed or have not fully responded to the vaccine.

They will have to swab the birds and test them for the virus, which can be spread on shoes, clothes, tires and even wind. Such measures would also reduce the risk of the virus spreading to humans or wild species, says Carol Cardona, a veterinarian and avian flu specialist at the University of Minnesota in the Twin Cities.

“Vaccines can help, but they’re not a golden bullet,” says Ron Fouchier, a virologist at Erasmus University Medical Center. He says this approach may require some culling as viruses continue to evolve and can sometimes avoid vaccines.

The current outbreak could make a difference as the virus spreads to many species of wild birds. If it becomes endemic in the US as well, then vaccination may become necessary, the researchers say. The USDA is modifying existing vaccines and testing new ones against the current strain of H5N1.

Overall, the Chinese poultry sector needs to prevent the spread of viruses in wild birds, Fouchier said. And European countries need to restructure to avoid a large number of farms with dense herds located close to each other, the researchers say, which is an even greater challenge than vaccination.

Cardona says it could take years to streamline and approve vaccines, as well as develop a vaccination strategy and reassure trading partners. “What are we waiting for?” she asks. “We need to work.”


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