Understanding the Ongoing Threat of Bird Flu: Six Questions Answered

The Netherlands must continue to watch out for bird flu, the disease that regularly kills bird populations, domestic and wild. That is the tenor of the letter which the Ministries of Agriculture, Nature and Food Quality, and Public Health sent to the House of Representatives on Monday. The letter discusses in detail the risks of bird flu for poultry, pigs, wild animals and people.

The ministries write in the letter to Parliament about the status of implementation Intensification plan for bird flu prevention, which dates from last July. This plan was drawn up in response to 78 recommendations from the Zoonoses Expert Group from 2021. Zoonoses are diseases that can make both animals and humans sick and can jump between the two.

The implementation of the measures is going well, the ministries report. That is only partly the case, according to Thijs Kuiken, bird flu expert at Erasmus MC in Rotterdam. “I am positive about the fact that things are not only happening in the poultry sector. On the other hand, I think: those recommendations are already 2.5 years old. Some things move unnecessarily slowly. Certain measures were already agreed in 2008 and have still not been implemented, such as strict separation of pig and poultry farming.”

What exactly is going on and should we be concerned? Six questions about bird flu.

1 What is the current status of bird flu?

We are still in a global outbreak of a so-called highly pathogenic variant of bird flu: a variant that makes poultry seriously ill. This variant emerged in poultry in Asia in 1996 and has increasingly swept through Europe since 2005. Things have been going extra fast since 2021, because the virus no longer disappears in the summer. In 2021-2022 alone, more than fifty million chickens and other poultry were culled in Europe, including more than five million in the Netherlands. Wild birds also become ill from it. They have now spread the virus all over the world, as far as Antarctica. Many mammals also die from it, such as 30,000 sea lions in South America.

Poultry behind the closed shutters of the stable. They are not allowed outside because there is a national lockdown requirement due to bird flu. Photo Marcel Berendsen/ANP

According to Kuiken, the Netherlands was relatively quiet in terms of outbreaks in 2023 – apart from the culling of 110,000 chickens in Putten in December. The lockdown requirement seems to help. “I think we have passed the peak in Europe,” he says, “also among wild birds. Probably some immunity has developed.” The virus continues to circulate among wild birds and continues to emerge in new species groups.

2 Why is the government so busy with bird flu?

Bird flu causes a lot of animal suffering and economic damage in the poultry sector. But the pig sector is also at risk: these animals can also contract bird flu. That’s a problem, because flu viruses can adapt quickly through mixing and genetic mutations. This allows them to adapt to their hosts, making them more transmissible or better able to evade the immune system.

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3 What is the risk for people?

The Dutch pig sector is a large mixing vessel in which bird flu viruses can mix with swine flu and thus adapt to mammals. An even bigger problem arises when a pig becomes infected with human flu at the same time. A variant may then arise that could cause the next pandemic in humans, such as in 2009 with the Mexican flu, which originated in pigs. It is impossible to say how likely this is to happen. But what is certain is that the virus only needs a handful of genetic adjustments to become pandemic. This has already happened in the past with other bird flu viruses (including the Spanish flu of 1918, which killed millions). And three of the necessary mutations have already emerged in mammals in Europe.

4 The prevention plan talks about vaccinations. What about that?

The RIVM, together with experts, has drawn up three scenarios with increasing severity. In the most serious scenario (circulation among people), measures such as quarantine or keeping distance may be necessary, the letter to Parliament states, “particularly to bridge the gap until vaccinations can be deployed.” This concerns bird flu vaccines for humans, which do not yet exist. This development takes approximately six months.

The prevention plan already provides for vaccination of professionals in the pig and poultry sector against the common seasonal flu. This can help prevent the mixing of human and animal flu. In the meantime, the effectiveness of two bird flu vaccines for poultry has been studied in Wageningen. These vaccines proved effective in the lab and are now being tested at companies. This will last until the end of 2025. If the vaccines still prove effective, a larger pilot will be started.

5 What other measures is the government taking to control bird flu?

The prevention plan also focuses on monitoring, prevention and preparedness. The RIVM, in collaboration with other parties, has set up a pilot to detect flu viruses on pig farms. Ninety companies were followed. The pilot will be continued; Ultimately this should lead to structural surveillance. In terms of prevention, a mandatory biosecurity plan for commercial poultry farms will be introduced by mid-2024. The ministries further write: “The government is aiming for a ban on new establishments of poultry farms in poultry-dense and water-rich areas and is exploring the options for a ban on expansion.”

6 All in all, are things going in the right direction?

“I found the surveillance pilot in particular very instructive,” responds Thijs Kuiken. In that pilot, several cases were found of people who were infected with swine flu (and recovered) and pigs who were infected with human flu. “But this was only a short and small pilot. Can you imagine how many cases there are in the entire pig sector, year after year? It is incomprehensible that this has not been monitored much more widely for much longer, if you know that this is a risk.”

The extensive testing of the vaccines to protect poultry against bird flu feels like a postponement operation to Kuiken, he says. “We now know enough that these vaccines are effective. Then start immediately with large-scale vaccination on companies. I suspect there are trade reasons behind this reluctance.”

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2024-01-30 19:19:32
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