Bird flu kills millions of chickens and turkeys in the US

bird flu

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A truck pulls out of the entrance to Cold Springs Eggs Farm, where the presence of bird flu was reportedly discovered, forcing the commercial egg producer to kill nearly 3 million chickens March 24, 2022 near Palmyra, Wisconsin.

An outbreak of highly pathogenic avian influenza in chicken and turkey herds has spread across 24 U.S. states since it was first detected in Indiana on February 8, 2022. Avian influenza, more commonly known as bird flu, is a family of highly contagious viruses that are not harmful to wild birds that transmit it, but deadly to domesticated birds. By early April, the outbreak had caused the culling of about 23 million birds from Maine to Wyoming. Yuko Sato, an associate professor of veterinary medicine who works with poultry farmers, explains why so many birds are getting sick and whether the outbreak threatens human health.

1. Why is avian flu so deadly to domesticated birds but not to the wild birds that transmit it?

Avian influenza (AI) is a contagious virus that affects all birds. There are two groups of AI viruses that cause disease in chickens: highly pathogenic AI and low pathogenic AI.

HPAI viruses cause high mortality in poultry and occasionally in some wild birds. LPAI can cause mild to moderate disease in poultry and usually little to no clinical evidence of disease in wild birds.

The primary natural hosts and reservoirs of AI viruses are wild waterfowl such as ducks and geese. This means that the virus is well adapted to them and these birds do not usually get sick when infected with it. But when domestic poultry, such as chickens and turkeys, come into direct or indirect contact with the droppings of infected wild birds, they become infected and show symptoms such as depression, coughing and sneezing, and sudden death.

2. There are multiple strains of bird flu. What is the nature of this outbreak and is it dangerous to humans?

The virus of concern in this outbreak is a Eurasian H5N1 HPAI virus which causes high mortality and severe clinical symptoms in domestic poultry. Scientists monitoring flocks of wild birds have also discovered a reassortant virus containing genes from both the Eurasian H5 and the low pathogenic North American virus. This happens when multiple virus strains circulating in the bird population swap genes to create a new virus strain, similar to how new COVID-19 strains such as Omicron and Delta have emerged during the ongoing pandemic.

According to the US Centers for Disease Control and Prevention, the public health risk from this outbreak is low. No human diseases have been linked to this virus in North America. This was also true of the last H5N1 outbreak in the US in 2014 and 2015.

3. Should people avoid poultry products until this outbreak ends?

No, that’s not necessary. Infected poultry or eggs do not enter the food supply chain.

To detect AI, the US Department of Agriculture oversees routine flock testing conducted by farmers and conducts state inspection programs to ensure eggs and birds are safe and virus-free. If H5N1 is diagnosed in a farm or backyard flock, state and federal officials will quarantine the site and kill and dispose of all birds in the infected flock. The construction site is then decontaminated.

After several weeks without new evidence of the virus, the area must be tested negative to be considered infection-free. We call this process the Four Ds of Outbreak Control: Diagnosis, Depopulation, Disposal, and Decontamination.

Avian flu cannot be transmitted by eating properly prepared and cooked poultry, so eggs and poultry are safe to eat. The USDA recommends cooking eggs and poultry to an internal temperature of 165 degrees Fahrenheit (74 degrees Celsius).

4. Are bird flu outbreaks more common around the world, or are we just hearing about it more than we did 20 or 30 years ago?

The dynamics of the spread of avian influenza viruses are very complex. HPAI is a transboundary disease, meaning it is highly contagious and spreads quickly across national borders.

Some research suggests that detection of HPAI virus in wild birds has become more common. Reports are seasonal, with a high in February and a low in September. There are ongoing outbreaks of HPAI in wild birds in Asia, Europe and Africa. Many migratory bird species travel thousands of kilometers between continents and pose an ongoing risk of transmission of the AI ​​virus.

In addition, we have better diagnostic tests for much faster and better detection of bird flu compared to 20-30 years ago, using molecular diagnostics such as polymerase chain reaction (PCR) testing – the same method laboratories use to detect COVID-19 19 infections use .

Concerns about bird flu outbreaks are rising, particularly among backyard chickens | FOX 9 KMSPThe 2015 bird flu outbreak decimated poultry populations across Minnesota, and turkey farmer John Zimmerman has been on high alert ever since. Subscribe to FOX 9 Minneapolis-St. Paul Watch FOX 9 Live: FOX 9 is your source for breaking news, live events, investigations, politics, entertainment, business news and local stories from Minneapolis -st Paul, …2022-03-16T03:21:37Z

5. What are the prospects for developing a poultry vaccine that could reduce the economic damage from outbreaks?

Many factors would need to be weighed before adopting vaccination as a strategy to combat HPAI. At this time, the Department of Agriculture has not approved the use of vaccines in the US to protect birds from avian influenza.

One reason is that the use of vaccines would potentially affect international trade and poultry exports. Importers would not be able to distinguish vaccinated birds from infected birds based on routine testing, potentially banning all US poultry exports.

Vaccination could also delay detection of outbreaks as it may mask non-obvious infections in infected birds. And if infections go unnoticed, they could spread to other farms before farmers can take control measures.

Avian flu vaccines can reduce clinical symptoms, morbidity and death rates in domestic poultry, but they would not prevent birds from contracting the virus. Ultimately, the USDA’s goal is to eradicate HPAI quickly once it is discovered. Vaccines could be used to fight an outbreak, however, and that’s one option the agency is currently exploring.

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By Yuko Sato, Associate Professor of Veterinary Medicine, State University of Iowa

This article was republished by The Conversation under a Creative Commons license. Read the original article. Bird flu kills millions of chickens and turkeys in the US

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