Dead bird avian flu concept

Highly Pathogenic Avian Flu Outbreak: Watch out for these ‘super-spreader’ bird species

Dead bird avian flu concept

Which species of birds are great spreaders of bird flu? New research from Tufts University offers details.

A new study by researchers at Tufts University details which species are super spreaders.

When it comes to bird flu, more commonly known as bird flu, not all birds are created equal.

“The scientific community has become accustomed to talking about influenza viruses in birds as a group, but birds are an incredibly diverse taxon of animals with different natural history, physiology and anatomy,” says Jonathan Runstadler , professor and director of the Department of Infectiology. Disease and Global Health at the 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 examines, from data, the influenza viruses circulating among different groups of birds and characterizes the types of birds involved in the spread of the virus. The timing of this article is impeccable, as a highly pathogenic strain of bird flu has spread across North America.

Great horned owl

In the current outbreak of highly pathogenic avian influenza, great horned owls are among the species that tested positive. Pictured: A great horned owl is treated at the Tufts Wildlife Clinic in 2019 (for injuries unrelated to avian flu). Credit: Alonso Nichols/Tufts University

This avian flu line originated around 1996 and was first discovered in a domestic goose in China. The virus mutated and persisted, and the first major outbreak of wild birds occurred around 2005 in a major wetland in Central Asia. Subsequent changes to the virus led to an introduction into the United States in 2014 via the Pacific Northwest, severely affecting the US poultry industry and forcing the culling of an estimated 40 million turkeys and chickens as a control measure. .

Influenza A virus H5N1 (A/H5N1) subtype is a subtype of influenza A virus that can cause disease in humans and many other animal species. A bird-adapted strain of H5N1, designated HPAI A(H5N1) for highly pathogenic avian influenza virus type A subtype H5N1, is the highly pathogenic causative agent of H5N1 influenza, commonly known as avian influenza or ” Avian Flu “.

“It was a blow,” says Nichola Hill, lead author of the paper and an assistant professor of biology at the University of Massachusetts Boston, who worked in Runstadler’s lab at the Cummings School for nearly five years. “After the end, we knew that we were between two epidemics and that there was a high probability of an epidemic reoccurring. We felt we needed to look at long-term historical data to find patterns and determine which birds are actually driving the global spread. So we compared birds on a finer taxonomic scale than previous studies like wild ducks, gulls, land birds, and geese versus domestic poultry like chickens, and got some really interesting results.

Historically, ducks like mallards have been thought to be super-spreaders of bird flu, infecting wild birds and backyard poultry, and research by Hill and Runstadler found that to be largely true. Dabbling ducks are powerful vectors for virus spread and virus evolution in the wild bird reservoir. They can carry highly pathogenic strains and be completely asymptomatic, in addition to swimming and flying, they can move the virus in a variety of ways, including local water bodies.

But there are other birds that play a bigger role in transmitting the virus. “When we looked at which birds were responsible for the spread in poultry, there were signs pointing to wild geese, which are really good at amplifying the virus,” Hill said. “We need to understand why in terms of their host’s pathology, immunity, behavior and ecology.”

Western sandpipers

A feeding frenzy of western sandpipers (Calidris mauri) during the mass migration through Cordova, Alaska – a key study site in the article. Credit: Wendy Puryear

One ecological factor that may play a role is that geese are grazers and thrive in cities and agricultural settings. Many species of geese in North America and Europe are considered pests. “They really are the perfect overflow host because they can use human-modified habitat,” Hill adds.

Additionally, understanding which birds are causing long-distance spread can influence how and when the virus enters a new geographic region. For example, the 2014 outbreak entered the United States via the Pacific, likely carried by ducks, but the current outbreak spread via the Atlantic, and ducks may not have been involved. to the same extent.

“The first wild bird detections in 2021 were large sea gulls,” says Hill. “Gulls are powerful pelagic birds that travel long distances and take advantage of tailwinds to travel over the ocean and move the virus around very quickly.”

An outbreak of bird flu of this magnitude and magnitude has never been seen before in North America. About 40 species of birds have been infected in the current North American outbreak, including songbirds like crows and sparrows, as well as raptors like owls and hawks. This outbreak has a greater geographic reach and impacts a greater diversity of species compared to the 2014 outbreak in North America.

“Knowing that gulls, geese and ducks can move this virus in different ways is a great contribution to understanding or possibly modeling with more

How well the measured value conforms to the correct value.

” data-gt-translate-attributes=”[{” attribute=””>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.”

Clinic Collaboration

Runstadler has been researching avian influenza since 2005, when his lab was located at the University of Alaska Fairbanks and the H5N1 strain of the virus was emerging in East Asia. 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.

Runstadler’s lab regularly collaborates with Tufts Wildlife Clinic and director Maureen Murray, clinical associate professor at Cummings School, to gather samples from a variety of birds coming through the clinic, not just the ones showing clinical signs of avian influenza. The goal is twofold: to understand the epidemiology of the virus and manage avian influenza cases safely in the clinic.

“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. Runstadler notes this exercise to gather data now is critical for comparison with data in the future. If a bird tests positive, the sample is sent to the USDA’s National Veterinary Services Laboratory for additional testing and sequencing as a final confirmation.

“We’ve seen some positive birds come through the clinic, including great horned owls, snowy owls, a bald eagle, and a peregrine falcon,” Murray says, “but fortunately, not a lot of cases.”

Risk to Humans

Though avian influenza is zoonotic, the risk to people is very low. Runstadler says there is practically zero threat to the average person going about their daily lives. It is of slightly more risk to people who handle birds regularly, such as wildlife professionals, poultry workers, or backyard chicken owners.

Recently, a man in Colorado was diagnosed with avian influenza, marking the first human case in North America during this outbreak. Media reports indicated he was involved with culling poultry and infected by a sick bird. According to the Centers for Disease Control and Prevention (CDC), he had mild symptoms, was isolated, and recovered. The fact that his symptoms were mild is paradoxically concerning because, Hill notes, it makes the virus harder to detect and track, as infected individuals may ignore mild symptoms and not seek treatment—much like

Hill is not only concerned about human spillover, but with mammalian spillover in general. She points to animals such as dogs, foxes or coyotes that may predate on birds, especially vulnerable ones showing neurological symptoms or in respiratory distress. It’s unclear at this point what the result of those interactions could be, though infections in red foxes have already been reported in the U.S., Canada, and the Netherlands.

Will This Outbreak End?

“The short answer is nobody knows,” Runstadler says, “because we don’t have a sophisticated enough understanding though we hope someday we will. It’s a very complex system.”

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. Also, this incursion seemingly has spread faster than the last one. In addition, Hill says her research has shown a pattern of the scale and magnitude of bird flu outbreaks increasing over time.

“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. Hill, Mary Anne Bishop, Nídia S. Trovão, Katherine M. Ineson, Anne L. Schaefer, Wendy B. Puryear, Katherine Zhou, Alexa D. Foss, Daniel E. Clark, Kenneth G. MacKenzie, Jonathon D. Gass Jr., Laura K. Borkenhagen, Jeffrey S. Hall and Jonathan A. Runstadler, 19 May 2022, PLOS Pathogens.
DOI: 10.1371/journal.ppat.1010062

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