Which bird species are super spreaders of avian influenza.

When it comes to avian influenza, more commonly called bird flu, all birds are not created equal.

“The scientific community has become accustomed to speaking about influenza viruses in birds as a group, but birds are an incredibly diverse taxa of animals with different natural history, physiology, and anatomy,” says Jonathan Runstadler, professor and chair of the Department of Infectious Disease & Global Health at Cummings School of Veterinary Medicine at Tufts University.

Runstadler is one of the authors of a new research study, published today (May 19, 2022) in the journal PLOS Pathogens, which takes a data-driven look at influenza viruses circulating among different groups of birds and characterizes which types of birds are involved in spreading the virus.

The virus mutated and persisted, and the first big wild bird outbreak happened around 2005 in a major wetland in central Asia.

A bird-adapted strain of H5N1, called HPAI A(H5N1) for highly pathogenic avian influenza virus of type A of subtype H5N1, is the highly pathogenic causative agent of H5N1 flu, commonly known as avian influenza or “bird flu.”.

So we compared birds at a finer taxonomic scale than prior studies such as wild ducks, gulls, land birds, and geese versus domestic poultry like chickens, and we came up with some really interesting findings.”.

Historically, ducks like mallards have been considered super-spreaders of avian influenza, infecting wild birds and backyard poultry alike, and Hill and Runstadler’s research found that to be broadly true.

Dabbling ducks are powerful vehicles for spreading the virus and for the evolution of the virus in the wild bird reservoir.

“When we looked at which birds were responsible for spillover into poultry, signs pointed to wild geese, which are really good at amplifying the virus,” Hill says.

“The first wild bird detections in 2021 were great black-backed gulls,” says Hill.

An outbreak of bird flu of this size and scale has never been seen before in North America.

About 40 species of birds have become infected in the current North American outbreak, including songbirds like crows and sparrows, as well as raptors like owls and hawks.

“Knowing that gulls, geese and ducks may be moving this virus in different ways is a big contribution to understanding or eventually modeling with more accuracy how we expect a virus like this to spread,” says Runstadler.

“Ultimately, we could put this data into a model that allows us to predict if there’s a virus emerging, when that virus might enter North America, and what bird populations we might target for surveillance to detect it.”.

The scientists in his lab study the ecology of influenza viruses in wild animal hosts, including birds, which are major reservoirs for influenza.

Runstadler says most flu viruses are thought to have originated in birds and spread to other hosts.

“When we admit new birds to the clinic, we sample them to see if they’re carrying the virus and isolate them until we get a negative test to make sure we’re not exposing our other patients to the virus,” says Murray.

The samples are screened at Runstadler’s lab to determine whether a bird is carrying an influenza virus, and if so, whether it’s the H5 strain responsible for outbreaks.

Recently, a man in Colorado was diagnosed with avian influenza, marking the first human case in North America during this outbreak.

The 2014 bird flu incursion gradually fizzled out, but that’s not likely to happen this time, he says, because the 2022 incursion is quite different from the last outbreak.

The viruses identified in North America in 2014 contained pieces of the highly pathogenic H5 viruses, but not the whole virus, like this outbreak.

“There’s reason to expect this virus is here to stay, and it’s not going to disappear,” says Runstadler.

Reference: “Ecological divergence of wild birds drives avian influenza spillover and global spread” by Nichola J.