Millions of birds are dying across the planet from Avian influenza

The A(H5N1) virus is accelerating the decline of the most threatened species. Reports of deaths also come where the virus has never been reported before

by Lorenzo Ciotti
SHARE
Millions of birds are dying across the planet from Avian influenza

Millions of birds are dying across the planet from Avian influenza. The A(H5N1) virus is accelerating the decline of the most threatened species. Reports of deaths also come where the virus has never been reported before. The explosive spread of the last two years is seriously worrying experts and scientists: in addition to Asia and Europe, the pandemic is spreading across the globe.

In South America, the virus reached Tierra del Fuego, but the pathogen also reached Antarctica and Australia. This year more than 40% of Peruvian pelicans have been exterminated, more than 100,000 gannets and more than 85,000 cormorants have lost their lives.

Ian Brown, director of scientific services at the UK's Agency for Animal and Plant Health, told the Guardian the case of Brazil, the world's leading exporter of chicken meat, which reported cases of avian flu in wild birds just 6 months after Peru.

Probably all avian species are susceptible to infection and all scholars agree that birds are the evolutionary melting pot of origin of all influenza viruses that would have adapted over millions of years. Wild birds are natural reservoirs (reservoirs) of the virus, especially aquatic species, in which all known subtypes of Orthomyxovirus type A circulate.

The virus is present in the intestine where it normally persists in an inapparent way (LPAI virus). Many of these birds are migratory and carry the virus to all parts of the world.

During stops near wetlands (ponds, river mouths) they encounter other species of migratory or sedentary or domestic birds, creating an ideal situation for interspecific contagion favored by the fact that most of the flocks are made up of more receptive young subjects.

Other groups, such as the columbiforms (pigeons, doves, turtle doves), the thurdids (blackbirds, fieldfares), hirundinids (swallows), sturnids (starlings and sparrows), seem not very receptive or even resistant. Birds of prey are sensitive but do not constitute an important reservoir.

Domestic birds are the middle link between wild birds and other domesticated animals. All species are affected (chickens, guinea fowl, geese, etc.). Turkeys are particularly sensitive. In felids, the first case of infection was reported in December 2003, in two tigers and two leopards from a Thai zoo who died from eating whole carcasses of infected fresh chickens.

In October 2004 there was an epidemic in another Thai zoo with the death/killing of 147 tigers out of 441. In these cases it should be noted that in the carcasses of the ingested chickens there was a significant viral load due to the intestines.

Cases have been reported in cats (also in Europe) and in civets and recently in dogs. However, in all these species considered the disease was sporadic and not epidemiologically relevant, even if evidence of the particular aggressiveness of the strain in question (H5N1).