2023-05-30 05:06:45
Poultry farms have recently become bird flu-free, but that does not mean that the virus no longer poses a threat. Wild birds still get sick. That is worrying, say bird experts. “Bird flu is an unpredictable virus that doesn’t just affect birds.”
Since the beginning of 2023, there are more than 2,000 dead black-headed gulls reported, and the number continues to rise. Traces of the HPAI virus, also known as bird flu, have been found in their carcasses. There is also an increase in the number of dead black-headed gulls in Belgium, France and Germany, reports the expertise center Dutch Wildlife Health Center (DWHC).
In addition to water birds such as gulls, waders and terns, birds of prey have also died from the virus. This is because birds of prey often eat carcasses of other birds infected with the disease. Last year there was also a lot of mortality among storks and spoonbills as a result of bird flu. According to DWHC, this shows that the virus is far from gone and leads to year-round mortality in wild birds.
“The problem is that the bird flu virus is mutating and new variants are constantly being added,” says Hanne Tersmette-Strijland of Vogelbescherming Nederland. “We also don’t know how long it takes for wild birds to become immune to the virus. It can just hit another bird species, for example because they mate with each other.”
An avian flu outbreak in 2016 mainly affected ducks, and many geese died in 2020. Since the outbreak in 2016, the virus has been found in more than sixty different bird species in the Netherlands, the DWHC reports.
Birds that breed in colonies are hit the hardest. This is because they live close together and have breeding grounds in places with a lot of water, from which they also drink. According to the expertise center, this is an ‘ideal combination’ for the avian flu virus to cause major deaths.
The special thing about the current bird flu in the Netherlands is that the disease started in poultry farms. There, large numbers of animals live close together in enclosed spaces, allowing the virus to spread quickly and mutate into other variants.
Confinement and shielding obligations contribute to less bird flu
Fewer poultry farms were affected by the avian flu virus last winter than in the winter of the previous year, according to Numbers from Wageningen University & Research (WUR). Last May, about 90,000 laying hens became infected with the virus, in January this year there were about 67,000.
At the beginning of this month, Dutch poultry farms even received bird flu-free status from the World Organization of Animal Health (WOAH).
“The fact that far fewer poultry farms are now dealing with bird flu is because various measures have been taken, such as the containment and shielding obligation,” says Evelien Germeraad, veterinary microbiologist at Wageningen Bioveterinary Research (WBVR). She has been researching bird flu in the Netherlands for years.
Of storage duty applies to poultry farms since October 2022. Companies must keep high-risk birds such as chickens and turkeys indoors in a stable, shed or shed. A shielding obligation applies to farms, zoos and hobby keepers, which means that the birds must live in specially shielded cages.
Both the containment and shielding obligations must prevent poultry from coming into contact with wild birds that are infected with avian flu. “In almost all cases where the virus has been found on poultry farms, it was caused by individual infections,” says the veterinary microbiologist. “Chickens, for example, become infected through wild bird droppings.”
Still a long way to go for vaccinations
Vaccines against bird flu are being developed to further combat infections on poultry farms. Two of the four vaccines that are tested are effective against the most contagious variants of the virus. But it will be a long time before animals in poultry farms can be vaccinated. At the moment, no vaccine has yet been approved for the European market.
Moreover, vaccines are impossible to combat avian flu among wild birds. “The virus can continue to spread among wild birds, because they live in the wild. It therefore remains a potential threat to poultry farming,” says Gemeraad.
Clean up dead birds quickly to prevent spread
Bird experts are concerned that the virus will also spread among mammals. Bird flu has recently been found in foxes and seals.
“Infections can go very quickly and also pose a risk to people,” says Hanne Tersmette-Strijland. According to the spokesperson for Vogelbescherming Nederland, there are already known cases of people who became infected with the virus. But there is no question of a possible outbreak in which humans or mammals infect each other.
“When you find a dead bird, it is very important that you do not touch it or clean it up yourself. You can become infected with the virus through the saliva,” she continues. “Always report it to the municipality or to the institution responsible for the site where you found the dead animal”.
According to Vogelbescherming Nederland, clearing up dead birds quickly can contribute to combating the virus. Tersmette-Strijland: “Actually, there should be a separate service for clearing up dead birds quickly. Now that is done by site managers and forest rangers, but in practice they don’t always have time for that.”
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