Bird flu, why we don't vaccinate birds

Bird flu, why we don't vaccinate birds

Bird flu

The wave of avian flu caused by the H5N1 virus – which has so far affected 76 countries, triggered national emergencies and is the worst animal disease epidemic in US history – continues to spread among wild birds and commercial poultry. According to the World Organization for Animal Health, more than 140 million birds worldwide have died from the virus or have been culled to prevent its spread. While more difficult to calculate, wild bird deaths have been catastrophic.

In the United States, where losses approach 60 million, industry experts have begun to tentatively discuss a measure they have long opposed: vaccinating commercial chickens, laying hens, turkeys and ducks against influenza.

At first glance, this would not seem a controversial idea: after all, influenza vaccines they are an established practice in humans, and chickens already receive several vaccinations in their first days of life. However, few countries routinely vaccinate poultry against avian influenza. In the United States, the adoption of a vaccine could trigger trade bans that would crush the huge export market, pit the poultry trade sectors against each other and possibly cause further safety concerns among consumers food.

After having killed hundreds of seagulls on Lake Garda, bird flu seems to be moving south The number of infections is said to be decreasing in the municipalities of Brescia. Instead, the first reports come from the province of Mantua. However, the risk to the population is considered low

Resistance and obstacles

Officially, therefore, the US industry opposes what would represent a drastic action. But in private - none of the people questioned wanted to speak officially - the scientists who collaborate with the poultry companies say they see no other way out. Even researchers working in industry point out that there may be few alternatives on the table, but also that the United States cannot embark on the path of vaccination alone.

" We are talking about vaccination on a global scale, because it would be a global decision and - says Karen Burns Grogan, veterinarian and associate professor at the Poultry diagnostic and research center of the University of Georgia (Georgia produces more broilers, broilers, than any other US state, about 1.3 billion annually 'year) – The decision should be made by everyone, from the World Organization for Animal Health to the federal government of the United States, down to trading partners ".

But that it comes to this decision is not discounted . In the United States, limited stockpiles of H5N1 avian flu vaccines — commissioned by the federal government after a huge outbreak in 2015 — may not contain the current strain, and the Department of Agriculture has not authorized their release anyway. use. Furthermore, expanding supplies to protect billions of birds would require a huge manufacturing effort, as well as a substantial manpower, since the injections would likely be administered by hand.

The debate is always more urgent. Bird flu continues to infect humans: the disease recently killed an 11-year-old girl in Cambodia and infected her father, albeit with a different strain than the one currently infecting birds and with no indications to lead one to think that the disease has spread from these people to others. Bird flu is also rapidly adapting to mammals, as evidenced by the recent deaths of some sea lions off the coast of Peru and farmed mink in Spain.

Bird flu is also killing an untold number , but presumably tall, of wildfowl. The trend represents a change from the historical pattern in which wild birds carried the virus but were not affected. "The impact on wild bird populations is unprecedented – explains Peter Marra, ornithologist and director of the Earth commons institute at Georgetown University -. A huge number of morus and other species have disappeared. And this not only in the United States, but across the Western Hemisphere, across Europe and, we assume, Africa as well.”

Additionally, outbreaks in poultry populations are on the rise, despite industry attempts to tighten biosecurity practices. These outbreaks cause enormous suffering in animals, prompting one leading expert to dub the disease “chicken Ebola.” A subset of US veterinarians highlights the cruelty of one of the most common methods of culling chickens in order to prevent the spread of disease: turning off the ventilation so the birds die from heat stroke. The impact on food supply must also be considered: in the United States, the loss of laying hens recorded last year reduced the availability of eggs by 29 percent, causing prices to double.

The consequences for trade

The ruinous effects of avian influenza on these hens highlight the obstacles to vaccination. The age to which each type of commercial poultry is allowed to live varies according to the purpose: where broilers reach their peak growth rate in six to seven weeks, it takes turkeys about six months to reach market weight; the layers and the "parents" of the broilers, on the other hand, can live a year or more, because the hens are not able to produce eggs before about 26 weeks. It is strange but noteworthy that the longest-lived varieties, layers and turkeys, appear to have suffered the greatest losses from the flu (this may be partly due to the fact that laying flocks host very large numbers of animals - in the order of millions per herd - causing the appearance of the virus to kill many more specimens). Layer and turkey farms, therefore, would benefit the most from vaccines.

The problem is that for the United States, the largest share of international poultry trade is not represented by eggs and turkeys, but by broilers , both for their meat and for waste that Americans don't want to consume, such as legs. Chicken meat exports earned the country more than $5 billion in 2021, according to the US Department of Agriculture. But many countries that buy US chicken have long refused to accept meat from vaccinated broilers, arguing that the immune response to vaccination and influenza infection is so similar that it is impossible to distinguish safe birds from those carrying the virus. In other words, the US poultry sector that has the least need of a vaccine is the one that is most at risk of using it, at least from an economic point of view.

Something is moving

The intensity However , the current surge of H5N1 in the world could subvert this logic . Last fall, the possibility of "removing unnecessary barriers" to the use of the avian flu vaccine was explored at an international meeting in Paris. In November, the European Union (EU) issued new regulations allowing poultry to be vaccinated under certain conditions, which will take effect this month. Since the beginning of the year, countries in Central and South America, where H5N1 has just arrived, have announced that they will start vaccinating poultry.

At the end of 2021, the US Department of Agriculture The United States has authorized a five-year research project with the aim of searching for new vaccines against avian flu, understanding how to prove their effectiveness and establishing whether the use of vaccines causes the flu virus to mutate.

A segment of the research community has argued for years that there is a clear way to distinguish between vaccinated and infected birds. The strategy, called Diva (acronym of the English expression meaning "to differentiate infected from vaccinated animals"), is able to create a molecular marker by replacing a protein of the strain used to produce the vaccine. When vaccinated chickens are tested, they show antibodies against the replacement strain instead of the wild type, thus demonstrating that their immunity comes from the vaccine and that they are therefore safe for commerce. This strategy was used twice in Italy, in 2000 and 2001, to stop outbreaks caused by H7N1 and H7N3 influenza strains in poultry populations.

The Italian example

" Other countries have always said that the costs related to vaccination – for the vaccine itself, but also for testing and potential restrictions on movement – ​​made it not worth it – explains Ilaria Capua, virologist and senior health fellow of Johns Hopkins Sais Europe in Bologna, who proposed using the system in Italy when he worked at the Istituto zooprofilattico experimental delle Venezie - But trade barriers can be eliminated if a system is applied which indicates that a group is vaccinated and is not been exposed to the virus ".

In Italy, the Diva system was then shelved when the multi-year wave of H7 strains faded (after however killing a Dutch veterinarian) and because other countries that at the time Those thought to be at risk did not have the budget or laboratory capacity to create a similar method. Today the context has changed, as the H5N1 flu has spread throughout the world. In addition to being a measure of the damage caused by the disease, the number of poultry and wild bird species affected is also an indication that the virus is finding many more hosts in which it can mutate into more virulent forms.

According to experts, acknowledging this reality makes it even more urgent to vaccinate poultry. We have known for a long time that avian flu spreads from wild to domestic birds in ponds, via droppings or by small birds. But it is possible that in these situations the flu also spreads to wild birds. And while vaccinating wild birds is unthinkable due to logistical constraints, vaccinating birds closest to us is within reach.

This article originally appeared on US.

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