The transmission of animal diseases to humans is not just a resource of dystopian movies -as in 12 monkeys- but it is a reality that has already happened. Some examples are “mad cow disease” or SARS, the protagonist of our latest covid-19 pandemic. This phenomenon of infection (zoonosis) is considered by the World Health Organization (WHO) as a serious threat.
This occurs because viruses adapt, through mutations. New variants emerge and acquire, in some cases, the ability to infect different hosts, in different territories. This is explained by Lucía Soliño, a technician from the SEO/BirdLife Marine Program, who warns about the rapid expansion that avian flu has experienced, thanks to these modifications, between the end of 2022 and the beginning of 2023.
The World Organization for Animal Health (OMSA) notes that birds are facing their worst pandemic to date. The H5N1 virus, a subvariant of highly pathogenic avian influenza, has spread rapidly to previously undetected regions of the world, in the southern hemisphere, after killing thousands of birds in the north.
In addition, the virus managed to make the leap and start infecting seabirds in the year 2021. “To date, the bird flu virus has been detected in some 400 different species of birds, but the outbreaks that are taking place in these In the last two years, they have mainly affected seabirds, something unusual up to now,” SEO/BirdLife points out in their study.
Soliño warns that “seabirds themselves face a multitude of threats: accidental captures, climate change, the decline in fishing groups and the introduction of mammals that prey on them”, and concludes that “this is yet another blow for all the species in this group of birds”, in declarations for this newspaper.
The most critical situations have been identified in the Atlantic gannet (Morus bassanus), with 75% of the colonies affected and 60% mortality; in the great skua (Catharacta skua), with a 70% reduction in the occupied territories in the British Isles; the Sandwich Tern (Thalasseus sandvicensis), with 20,531 dead adults in two months; the frowned pelican (Pelecanus crispus), which accumulates a loss of 40% of its European population, 10% of its global population and the black-headed gull (Chroicocephalus ridibundus), with some 10,000 deaths in the United Kingdom alone.
SEO/BirdLife warns, however, that these numbers are possibly greatly underestimated, due to the difficulty of recovering the animals once they have died and because not all colonies have long-term population estimates that allow interannual comparisons.
The pandemic started in the summer of 2021, according to SEO/BirdLife records, after some mass mortalities in the northern hemisphere (UK and North America). At the beginning of 2022, the same thing was repeated in various parts of Africa, such as the Djoudj National Bird Park (Senegal), one of the most important ornithological reserves in the world. In the spring of that same year, it was Europe’s turn.
At the end of 2022 and the beginning of 2023, the virus had reached the south of the American continent for the first time in history, affecting a large number of species, including marine mammals. In just four months of 2022, 22,000 dead birds were counted on the coasts of Peru, mainly Peruvian pelicans, and at the beginning of 2023 several thousand sea lions were stranded.
“2023 does not point to improvements. Seabird colonies continue to be devastated by influenza and there is concern about their rapid expansion and adaptation to new hosts,” presents SEO/BirdLife.
In Spain, over the past year, cases have been detected in Andalusia, Catalonia, Galicia, the Basque Country, Aragon, Castilla y León, Castilla la Mancha, Cantabria, Extremadura, Madrid, La Rioja, Asturias, Murcia and Valencia and are of particular concern outbreaks in the Albufera de Valencia and Delta del Ebro natural parks. In the former, more than 1,000 carcasses of Sandwich terns and Eurasian terns have already been removed, but it is unknown how many are due to the flu.
In total, more than a hundred cases have been observed in wild birds -117, specifically-, and the risk of populations of sensitive species has intensified, such as the Sandwich Tern (Thalasseus sandvicensis) and the Black-billed Squab (Gelochelidon nilotica). Mortality in this group is, according to Soliño, higher than in poultry.
