Containment measures against bird flu have been effective so far, but “they are no longer enough”

Avian influenza is one of the most devastating animal diseases. Since the end of 2020, the world has witnessed the worst epidemic in the history of this virus, caused by the highly pathogenic H5N1 subtype belonging to the 2.3.4.4b clade. The virus has killed millions of poultry around the world and is having an unprecedented impact on the health of wild birds, particularly in Europe and the Americas. Additionally, the disease has affected many wild mammals and even domestic cats.

In a recent presentation organized by the Organization of Colleges of Veterinary Medicine (OCV), Elisa Perez RamirezThe Doctor of Veterinary Medicine, Virology, Department of Infectious Diseases and Global Health, INIA-CSIC Animal Health Research Center, presented the current status of H5N1 avian influenza in birds, domestic cats and wild mammals.

unprecedented crisis

The natural reservoir of viruses is wild waterfowl, where so-called low-pathogenic avian influenza viruses circulate freely. “The problem starts when domestic birds are exposed to these low-pathogenic viruses from wild animals,” explains Pérez Ramirez.

Once the virus enters a poultry farm, “it starts to spread very strongly, and through a process of recycling and mutation, Can be transformed into highly pathogenic avian influenza virusbut this only happens in two specific subtypes, namely H5 and H7“. The results are often devastating, with many animals dying within a short period of time,” the researchers noted. Furthermore, he added that with the H5N1 subtype, the virus can return to wild birds and “lead to the death of many humans.”

Regarding the risk to human health, it must be emphasized that “various subtypes of avian influenza spread sporadically from birds to humans, but H5 and H7 are the most problematic, with two of the possible combinations meaning is huge health challenge Because they cause human deaths and the outbreaks are very widespread. ” its about H5N1

H7N9, which currently causes the most damage, and H7N9, which causes huge mortality but has not yet spread.

“This is the most devastating disease in the poultry industry and one of the most devastating diseases in animal health”highlight the doctor. They have died since the H5N1 subtype was first discovered in 2005 479 million birds, according to WHOA data. “Furthermore, more than half died in the past three years.”

Global expansion of the virus

During the epidemic waves in 2020 and 2021, the virus has spread throughout Europe, Asia and Africa, but there has been no outbreak in the Americas. The situation changed dramatically during the season from October 2021 to May this year, as “the virus managed to spread from Europe to the Americas, from where its geographical range fully expanded and followed the migratory routes of birds,” within a few months, The virus has successfully spread from the United States to the southern tip of Argentina. ”

It is worth mentioning that Australia and Antarctica have not yet been infected. “This is particularly important because there are now infected wild birds in the far south of Argentina, very close to Antarctica, Virus could reach Antarctica during migration this fall We don’t know what impact this might have on wild birds there. ”

A total of 31 poultry epidemics and 52 wild bird epidemics occurred in Spain during the 2021-2022 season. This number is far lower than other European countries. At the same time, in the 2022-2023 season, the epidemics of free-range animals have decreased, but the epidemics of wild animals have increased. “had a very serious impact on coastal seabirds” said the expert.

Impact on wild birds

The impact on wild birds is very worrying. “At least 375 species of wild birds have been infected in the past three years”to the point that “the virus is already endemic in wild populations over large geographic areas,” meaning there is an ongoing risk of transmission to poultry farms.

As an example of this situation, he mentioned the case of Peru, where 220,000 wild birds died from November last year to March this year. In fact, about 20 percent of the nation’s pelicans died during those five months. “This is just in Peru, where excellent work is being done to count and monitor wild populations.” Meanwhile, in Europe, Colonial seabirds most affectedEspecially black-headed gulls, terns and herring gulls.

Virus-related complications

Since entering 2021, the situation has become complicated The epidemic is no longer seasonal. As the veterinarian lamented, “Now they occur year-round, whether in domestic or wild animals, which requires maintaining high biosecurity measures and having new tools to permanently assess and control risks.”

On the other hand, eradication programs based on virological surveillance, slaughter, disinfection and restrictions on the movement of birds and their products have been effective so far. However, they are no longer enough. “We will need complementary tools, with vaccination being the most prominent.

”, but the rapporteur stresses that this solution must be accompanied by a comprehensive surveillance and control plan. In this sense, he gave the example of mass vaccination in France.

Transmission to mammals with increasing frequency

Pérez Ramirez stressed that the virus “poses huge risks to biodiversity”, because not only wild birds are affected, but also many wild mammals. In fact, previously, specific transmissions occurred in mammals, like foxes. However, in recent years “Extremely rich and diverse jumps occur in many wild mammal species“. These include some marine mammals and wild species such as otters, ferrets or badgers. In South America, for example, sea lion mortality is very high.

on the other hand, Doctors stress severity of situation on fur farms. Last October, the first major poultry outbreak broke out at a mink farm in Galicia, killing more than 50,000 animals and putting the world on alert. However, this is not the only case, outbreaks have recently been detected on 27 fur farms in Finland. “Transmission between animals and between farms is very possible,” Peres explained of the crisis that has not yet stopped in Finland.

In addition, he mentioned a publication that revealed that “mink farms pose a huge risk to future epidemics of virus origin”, which is why strong government measures are necessary. “If these facilities are not closed, their biosecurity can at least be greatly improved and very rigorous active monitoring of such farms can be carried out.”

Viruses in domestic cats

Last summer, there was a serious outbreak among domestic cats in Poland. Researchers in the country acted very quickly and conducted relevant genetic analysis to prove that the viruses were actually the same and, therefore, “There may be a common source of infection”. However, there was no clear pattern in the geographical distribution of affected cats or their contact with the outside world (some cats left the home, but others did not). In the end, the scientists concluded that this was most likely through infected: contaminated food

.

Sporadic outbreaks have since occurred outside Poland, some caused by the ingestion of raw or poorly processed meat, as was the case in South Korea. One of the strangest cases occurred on an Italian farm where an outbreak of bird flu occurred this year. After the virus spread, pets living on the farm were tested and one cat and four dogs were found to be infected with avian influenza but showed no symptoms. “Asymptomatic infection in pets may have serious consequences for public health”, warns the veterinarian.

In this sense, he states that “The more species of mammals are infected, the closer the virus comes to humans., in a sense, we are giving it a chance to adapt to mammalian cells. ” Even so, avian influenza is a disease very specific to birds and is difficult to transmit to humans, and “only after close and prolonged contact with an infected animal,” the speaker clarified. In fact, Only 14 cases have emerged in humans since 2020. Furthermore, infection always occurs through close contact with poultry, except in the case of a man in Chile who may have been infected through a wild animal.

Anyway, please remember The consequences of this animal pandemic are manifold.Among them, the huge economic impact, the huge threat to wildlife conservation, and the risk of jumping zoonotic diseases are particularly prominent. After recommending seasonal influenza vaccination to all professionals who come into contact with susceptible animals, the veterinarian concluded his presentation with an observation about the urgency of the crisis. “When transmission from animals to humans has occurred, the cost of controlling an outbreak increases exponentially”, so it is now necessary to monitor the animals.