Officials have confirmed that a highly pathogenic strain of bird flu has been detected in Nevada for the first time, spreading across the United States since late 2021.
The species, known as Eurasian H5N1, was discovered earlier this month in a non-commercial flock of 40 domesticated birds in Carson City. The affected birds were euthanized and did not enter the food system, but Nevadans — especially those who own or work with poultry — must remain vigilant for signs of disease in wild and domestic birds.
Avian flu occurs naturally in wild waterfowl around the world and can circulate among those birds, often with little or no signs of illness and low death rates. In particular, dabbling ducks, such as the mallard, are considered reservoirs for bird flu because they are often asymptomatic for the disease.
The problem arises when waterfowl spread the flu to more susceptible birds, such as chickens, turkeys and birds of prey. In these vulnerable birds, highly pathogenic avian influenza can lead to death rates of 90 to 100 percent, often within 48 hours.
But because avian flu is highly contagious and many wild birds can host the flu without serious symptoms, it’s difficult to control the spread of the disease.
“There’s not much we can do in terms of wildlife,” says Dr. Nate LaHue, wildlife veterinarian for the Nevada Department of Wildlife. “It should be about killing large numbers of waterfowl, which is not a practical response.”
Birds can easily lose the virus in their saliva, nasal secretions and feces, so any bird that comes into contact with an infected bird is at serious risk of infection. Birds can also become infected if they come into contact with surfaces contaminated with the virus by other birds.
The U.S. Department of Agriculture estimates that more than 40 million domestic birds have been affected by the current outbreak, and avian flu has been diagnosed in nearly 1,900 wild birds in the U.S. as of late 2021.
LaHue said migratory birds likely brought the disease to North America, which is why it’s spreading so quickly. Currently, there are 44 states where the current bird flu strain has been detected in wild birds and 38 states where bird flu outbreaks have occurred in poultry.
While there have been no confirmed cases of avian influenza in Nevada wild birds so far, LaHue said it’s likely the flu is already in the state’s wildlife population. The wildlife department is investigating several suspicious deaths from birds of prey, and LaHue said at least one death, an owl, is likely linked to the current form of bird flu.
The Department of Wildlife also says that while most infections have occurred in domestic or wild birds such as waterfowl, game birds and scavengers like crows, people should consider all birds susceptible. LaHue said there is high mortality of some species of geese and cormorants from outbreaks across the country.
Eurasian H5N1 has also been found in mammals such as foxes, coyotes and bobcats, and the wildlife department said “all mammals should be considered potentially susceptible.”
Humans are one of those potentially sensitive mammals. But the U.S. Centers for Disease Control and Prevention and the World Health Organization say the current strain of bird flu poses little threat to the general public.
To date, only one case has been reported in the US of a person contracting the current strain of the virus. That person was directly exposed to infected poultry as part of a cull operation and has made a full recovery.
Nevertheless, the Nevada Department of Agriculture has drawn up a list of biosecurity measures for people who work with birds so they can protect themselves and their flocks from avian flu.
LaHue advised poultry farmers to take steps to reduce the amount of contact between domestic and wild birds, and he warned the public to do things like feed waterfowl, which could cause the birds to congregate artificially and potentially increase transmission.
While the symptoms of bird flu can vary widely, people should be aware of respiratory or neurological abnormalities in birds, as well as skin-related problems, diarrhea or discolored stools, weakness, lethargy, and depression.
In addition, the State Department of Wildlife is currently monitoring outbreaks of bird flu. If you notice three or more dead birds, a single bird of prey dead, or a bird exhibiting respiratory or neurological abnormalities, report it to the agency at (775) 688-1500 or ndowninfo@ndow.org.
Colton Poore is a 2022 Mass Media Reporting Fellow through the American Association for the Advancement of Science. Email him at cpoore@reviewjournal.com or follow him on Twitter @coltonlpoore.