Backyard chicken keeping has seen a major surge in popularity over the last decade. However, with the recent outbreaks of highly pathogenic avian influenza (HPAI) in commercial poultry flocks, many backyard chicken keepers are understandably concerned about the risk of avian flu in their flocks. Here we’ll take a look at the key questions around avian flu and backyard chickens.
What is avian influenza?
Avian influenza refers to infection with any of the influenza type A viruses that commonly infect birds. These viruses occur naturally in wild aquatic birds worldwide and can infect domestic poultry and other bird and animal species. Avian influenza viruses are classified into two categories based on their ability to cause disease: low pathogenic avian influenza (LPAI) and highly pathogenic avian influenza (HPAI).
Most LPAI viruses cause little or no signs of illness in infected birds. However, some LPAI virus strains are capable of mutating into HPAI variants. HPAI viruses cause severe disease and death in poultry. Both LPAI and HPAI viruses can be spread between birds through direct contact or through indirect environmental exposure to virus shed in respiratory secretions, saliva, nasal discharge, and feces of infected birds.
What strains of avian flu are currently circulating?
There are many different subtypes of avian influenza virus distinguished by the combinations of proteins found on their surfaces. The virus subtypes currently circulating and posing the greatest risk are:
- H5N1 – first emerged in Asia in the late 1990s and has caused outbreaks in poultry and wild birds in Asia, Europe, Africa and the Middle East. Rare human infections have occurred from direct bird contact.
- H7N9 – first detected in China in 2013. Causes poultry outbreaks and serious human illness in China. Low risk of transmission between humans.
- H5N2, H5N8 – first detected in the U.S. in wild birds and backyard and commercial poultry flocks between 2014-2015. Outbreaks have continued annually during migration seasons.
How are backyard flocks being affected?
Backyard and hobby flocks located near wild bird habitats face a higher risk of exposure to avian influenza viruses through contact with infected migrating waterfowl. LPAI and HPAI outbreaks have occurred in non-commercial backyard flocks in the U.S. in recent years:
| Year | Number of backyard flocks affected |
|---|---|
| 2014-2015 | 211 |
| 2016-2017 | 17 |
| 2018-2019 | 8 |
| 2020-2021 | 92 |
The table shows that larger backyard flock outbreaks occurred in 2014-15 and 2020-21, likely associated with novel HPAI virus introductions from wild birds during spring migration seasons. Smaller numbers of non-commercial flocks were affected in the intermittent years between migration seasons.
Regional differences in backyard flock outbreaks
Backyard flock outbreaks have occurred in multiple U.S. regions, but the highest numbers have occurred in the Pacific and Central flyways where wild waterfowl overlap with poultry productions areas:
| Flyway | Number of backyard flocks affected 2014-2021 |
|---|---|
| Pacific | 157 |
| Central | 119 |
| Mississippi | 32 |
| Atlantic | 20 |
What precautions can backyard flock owners take?
Backyard flock owners should follow good biosecurity practices to reduce the risk of avian influenza introduction:
- House birds indoors or under a covered enclosure if possible during migration seasons
- Restrict contact with wild birds by covering outdoor enclosures with netting
- Disinfect shoes and equipment between enclosures
- Isolate new birds for 30 days before introducing to flock
- Avoid introducing birds from sources with unknown health status
- Report signs of illness or unexpected deaths to state veterinarians
What are the symptoms of avian influenza in backyard flocks?
LPAI may cause mild respiratory or reproductive signs. HPAI frequently causes one or more of the following symptoms:
- Sudden increase in bird deaths
- Lethargy and loss of appetite
- Decrease in egg production
- Swelling around eyes, neck and head
- Purple discoloration of wattles, comb and legs
- Difficulty breathing
- Nasal discharge, coughing or sneezing
- Lack of coordination or diarrhea
However, HPAI can also strike flocks suddenly without warning signs. Flock owners should report any unusual signs of illness or unexplained mortality to state animal health authorities.
Can avian influenza be transmitted from poultry to humans?
Avian influenza viruses do not normally infect humans. However, sporadic human infections with certain avian influenza subtypes have occurred, typically after close contact with infected birds or heavily contaminated environments.
From 2003 through 2022, a total of 868 laboratory-confirmed human cases of H5N1 virus infection have been reported to the World Health Organization from 20 countries. 457 of these cases were fatal. The vast majority of human H5N1 cases have occurred in Africa and Asia from direct household exposure to infected poultry.
In the U.S., only one human case of H5N1 virus infection has ever been detected. This involved a Colorado man who had exposure to his infected backyard flock during culling activities in April 2022. He recovered after a few days of mild symptoms.
While human infection remains rare overall, backyard flock owners should use protective clothing and equipment when handling sick or dead birds to avoid virus exposure as a precaution.
How are avian influenza outbreaks handled in backyard flocks?
Once avian influenza is confirmed in a backyard flock, state veterinary authorities will quarantine the site and likely order the culling (depopulation) of the infected flock. Proper disposal of dead birds and contaminated materials, followed by thorough cleaning and disinfection of the site and equipment, is necessary. Sentinel birds may be placed after an appropriate down time to confirm the virus has been eliminated before allowing the area to be re-populated.
The USDA provides indemnity payments to flock owners to compensate for birds and materials lost during an avian influenza outbreak response. However, compensation is generally only provided when flocks are registered through the National Poultry Improvement Plan (NPIP) prior to a disease event occurring.
Conclusion
Backyard poultry flocks remain at risk for avian influenza virus exposure from wild birds, particularly during spring migration seasons. However, the overall numbers of non-commercial flocks affected has been low relative to large commercial operations with less stringent biosecurity practices. Backyard flock owners who follow good biosecurity practices, monitor their birds closely, and report signs of illness promptly play a critical role in helping to detect and contain avian influenza virus outbreaks.
