Highly Pathogenic Avian Influenza

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What is highly pathogenic avian influenza (HPAI)?

Avian influenza, also known as bird flu, is caused by the influenza type A virus. It can affect domestic and wild birds, but waterfowl (ducks, geese, etc.) act as the primary viral reservoirs even though they may not appear sick. As a result, the risk of transmission of the virus to backyard poultry flocks increases during waterfowl migrations. It can also be spread between backyard flocks and by imported birds. Indoor birds have a low risk of infection, but companion birds that live outdoors may spread the virus. The disease is found worldwide, but subtypes tend to be prevalent in specific regions.

Avian influenza viruses are generally spread through feces and respiratory secretions from infected birds, either through direct contact, in contaminated food and water, or on equipment. The incubation period ranges from a few days to two weeks.

Strains of avian influenza are categorized based on the combination of 16 hemagglutinin (H) and 9 neuraminidase (N) proteins. They are further classified as “low pathogenic” or “highly pathogenic” based on their ability to cause disease in chickens. Influenza viruses change constantly, and some low pathogenic avian influenza viruses can evolve into highly pathogenic avian influenza viruses. Highly pathogenic avian influenza viruses are primarily H5 and H7 strains (although not all H5 and H7 viruses are highly pathogenic) and can spread rapidly in poultry flocks, causing serious illness and death during outbreaks.

Although isolated cases of human infections have occurred, strains of avian influenza found in the U.S. typically do not affect humans. People with high occupational or recreational exposure, such as poultry producers and hunters, may be at greater risk of infection.

What are the clinical signs of highly pathogenic avian influenza (HPAI)?

Highly pathogenic avian influenza strains are highly contagious and often cause fatal disease in birds.

Signs of disease in birds can appear within three to five days of exposure and include:

• Inflamed heads, eyes, wattles, or combs
• Trouble breathing
• Diarrhea
• Lethargy
• Eating or drinking less
• Stumbling or falling
• Soft/misshapen eggs
• Sudden death

The World Organization for Animal Health (OIE) has designated avian influenza as a reportable disease. Contact the state animal health official if you suspect a bird or flock is infected with avian influenza.

How is highly pathogenic avian influenza (HPAI) diagnosed?

Currently, the main confirmatory tests for HPAI infection are detection of viral genetic material (RNA) by quantitative reverse transcription polymerase chain reaction (qRT-PCR) or isolation of the avian influenza virus from oropharyngeal (back of the throat) and/or cloacal swabs. Specific viral subtypes (H5N1, etc.) are determined by genetic sequencing through national reference laboratories such as the National Animal Health Laboratory Network laboratories.

Are there any treatments for highly pathogenic avian influenza (HPAI)?

Unfortunately, there are no treatments for avian influenza. Since it is highly infectious and there are no treatments or commercially available vaccines, the best recourse is to prevent further spread of the virus to other susceptible birds.

What should I do if I suspect my flock has HPAI?

To report an unusual number of sick or dead birds with similar, contact the Sick Bird Hotline at 866-922-BIRD (2473).

What is the prognosis for highly pathogenic avian influenza (HPAI)?

To date, recovery from HPAI is very rare. During outbreaks, birds are often culled to prevent further spread of the disease. Since HPAI is a reportable disease, state animal health officials provide advice on the specific steps to take with infected animals. Based on the specific diagnosis, quarantine, euthanasia and disinfection of the coop area may be considered.  

How can highly pathogenic avian influenza (HPAI) be prevented?

The best way to prevent avian influenza infections is to follow proper biosecurity protocols.

The CDFA recommends the following biosecurity practices to prevent the spread of HPAI (https://www.cdfa.ca.gov/ahfss/Animal_Health/Avian_Influenza.html):

• Wash your hands before and after handling your birds. This includes when moving from coop to coop.
• Prevent contact between domestic and wild birds by bringing your birds indoors or ensuring their outdoor area is fully enclosed and covered.
• If you have bodies of water on your property such as ponds or ditches, consider draining them to avoid attracting wild birds, and keep your domestic birds away from this potentially contaminated water.
• Use sanitized well or city water for your birds.
• Prevent rodents and predators from entering your coop.
• Keep feed covered and spills cleaned up to avoid attracting wild birds and rodents.
• Wash and disinfect booths and equipment when moving between coops.
• Do not share equipment or supplies with neighbors.
• Clean and disinfect equipment and other supplies between uses.
• Clean and disinfect your shoes and vehicle tires after visiting feedstores and other places frequented by other poultry owners or wild bird hunters.
• Avoid visiting places where wild birds congregate such as lakes and ponds.

For more information

Bird Flu Current Situation Summary, Centers for Disease Control and Prevention (CDC)

Avian influenza updates, California Department of Food and Agriculture (CDFA)

Information for Specific Groups that are in contact with birds/poultry

Highly Pathogenic Avian Influenza, University of California Agriculture and Natural Resources (ANR)

Poultry Owners Urged to Protect Birds From Avian Influenza Virus, UC Davis School of Veterinary Medicine News, April 2022

*This article may not be reproduced without the written consent of the UC Davis School of Veterinary Medicine.