The chickens have not yet received the influenza vaccine. The virologist wants to hurry

Avian flu is not at the top of the political agenda in the Netherlands. This is the conclusion of Thijs Kuiken, a virologist and professor at Erasmus MC in Rotterdam and a member of the Dutch and European working groups advising on the avian approach. “Vaccinating poultry against influenza is now a priority, both to prevent further slaughter and because of the health risks to humans,” Kuiken says.

The European Communicable Disease Service ECDC reported in October that the current outbreak of bird flu in Europe is the largest on record. Since this pandemic began in October 2021, about 2,500 outbreaks have been reported in Europe in poultry farms and more than 3,500 outbreaks among wild birds, from Spitsbergen to southern Portugal and Ukraine. About 50 million chickens and other poultry have been culled, including 5 million in the Netherlands. Last month, the Dutch counter reached nearly 900,000, of which 300,000 were in one company.

Trade is not prohibited

The president of the Dutch Poultry Farmers Association said earlier this year that the Dutch Poultry Farmers Association supports vaccination. But given the conditions: There should be no trade barriers and the vaccine should be really good. It should not only prevent infection and disease, but also the transmission of the virus: otherwise it can spread unnoticed.

“If you read the European rules carefully, you’ll see that there are really no trade barriers,” Kuiken says. Preventive vaccination is permitted as a long-term strategy. Countries can decide for themselves.” In other words, there is no law preventing the trade in vaccinated poultry. “Just: Everyone thinks this is the case. That is why the cultivators do not want to touch it.”

The LNV Ministry is aware of this, the spokesperson replies, and Europe is working hard to find a solution. The 2023 draft regulation already states that the trade in meat from vaccinated animals is permitted, provided the animals are free of infection. Monitoring rules are now being established for this purpose.”

In the Netherlands, only a vaccine based on a low-pathogenic strain has been registered

However, this practice is not regulated, as the ministry also sees it: “So the EU rules do not stand in the way of vaccination, but they impose additional conditions on trade. This can entail costs for market parties. In practice, companies in the union can European or elsewhere refuse products from vaccinated animals. They are free to do so.”

Mart de Jong, a professor of quantitative veterinary epidemiology at Wageningen University & Research, who researches avian flu vaccines, says pre-vaccinating with existing vaccines is not a good idea. In the Netherlands, only a vaccine based on the so-called low pathogenic strain has been registered since 1986, he says. “This does not work well against the current highly pathogenic avian influenza.”

Read also: Avian influenza is always around. Why are virologists holding their breath now?

So why aren’t pharmaceutical companies working hard on better vaccines? De Jong sees the problem with chicken eggs. He says: “European countries only want to trade among themselves in unvaccinated poultry, because it is difficult to distinguish between vaccinated animals and diseased animals.” Because there is no international market for vaccinated animals, poultry farmers are reluctant to vaccinate their animals – and pharmaceutical companies are reluctant to invest in better vaccines.

In any case, manufacturers must constantly adapt their vaccines to the prevailing variant of avian influenza, just as they are currently doing with human influenza vaccines. De Jong confirms that something else is going on. “Many of the current vaccines work well in the lab, but their effectiveness in this field is disappointing,” he says. This is especially true of conventional vaccines, which consist of an inactivated virus. We see much smaller amounts of antibodies in the field. The question is whether this is also the case with newer types of vaccines. We’re looking into that right now.”

broader immune response

If the amount of antibodies is too low, the vaccine will not protect well against virus transmission. The vaccinated animals can then transmit the virus to each other. “Then you lose control of the spread,” says De Jong. “And then people can be exposed to the virus without being noticed.”

Experts hope this will be different with the latest generation of vaccines. They are more complex – just like Corona vaccines, for example – and guarantee a broader and longer-lasting immune response. De Jong: “But whether and if this helps protect birds from transmission of the virus with low antibody levels is not yet clear.”

At the end of 2021, the ministry released funds to research better vaccines. This is happening now in Wageningen. “We are investigating, among other things, how to better stimulate immunity with new types of vaccines and how you can prevent transmission in practice.”

In any case, newer vaccines make it possible to distinguish between sick and vaccinated animals. These vaccines no longer consist of whole, inactivated virus, but are based on a specific surface protein from the related virus: hemagglutinin protein in the case of avian influenza virus, and spike protein in the case of coronavirus. Therefore, the immune system only makes antibodies against them; You can see this in a blood test.

Silent trading

Meanwhile, Professor Theijs ​​Koiken urges more urgency. He says: “In an emergency you have to take emergency measures, in which case a vaccination as soon as possible. As far as I am concerned, that should have been possible right after 2003.” Then there was the spread of a highly pathogenic variant in Dutch poultry farming. More than 30 million birds have been culled and a veterinarian has died from the virus.

The argument that current vaccines provide inadequate protection against transmission of the virus does not carry enough weight in Koiken’s view. “Such a vaccine in any case limits the amount of virus circulating,” he says, “and thus also the risk of further outbreaks and dangerous mutations of the virus. And we know from the literature that ‘silent circulation’ does happen. I think you can only limit that better. by vaccination.”

The greater the spread of the virus, the higher the chance of dangerous variants

Ministry of Agriculture, Nature and Food Quality more careful. “You can’t say in advance that the vaccine will reduce the amount of virus circulating,” says the spokesperson. “Before we start vaccinating in practice, with possible unforeseen consequences, they must first be sorted out. This is happening now in Wageningen. We also need this information so that we can set up a well-founded monitoring programme.”

According to Mart de Jong, the current method of surveillance is a reason not to vaccinate with suboptimal vaccines in advance: “Poultry disease is now an indicator of infection on the farm. If there is no disease after vaccination, but there has been transmission of the virus, there may be greater spread In the end “.

You can avoid this problem by tweaking surveillance, Quicken says: by checking for antibodies against the entire virus. “So we need to invest more in monitoring and biosecurity on farms,” ​​he says. “Of course we have to take a critical look at the high density of poultry in our country.”

risks to humans

He cites another argument for acting more quickly in all of these areas: risks to human health. The type of virus now circulating in Europe has already infected people: one in England, one in the United States and two in Spain. In Asia, people die every year from the variant circulating there.

The more the virus circulates, the greater the chance that mutations will create a variant that is easily transmitted from person to person, or ‘mixed’ with the human seasonal influenza virus, and thus could cause a pandemic. “We’ve seen that in the past,” Kuiken asserts. “The 1957 Asian flu and the 1968 Hong Kong flu are both associated with avian influenza viruses.” Both epidemics claimed 1 to 4 million lives.

“However, the Dutch government does not currently treat avian influenza as an animal disease,” Koeken says, as a disease that can also affect humans. There is now a group of experts in animal diseases advising the ministry on this matter. But the other expert group, the zoonotic disease expert group, was not involved. In addition to veterinarians and biologists, this also includes doctors. So this group has different considerations.”

Why doesn’t the government also summon the other group of experts? “I call this cognitive dissonance,” Koeken emphatically replies. “It’s easier to ignore that human side.”

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