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How to protect your flock from avian influenza (AI)

May 9, 2022
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Avian influenza viruses spread through direct contact with infected birds or through contaminated feed, water, equipment and clothing.

Reports of avian influenza (or bird flu) are currently resurfacing around the world. Cases of H5N1 HPAI have been confirmed in many countries and various regions of Asia, Europe and North America, affecting both the commercial and wild bird populations. Thus far, more than 31 million birds have been culled this year in an effort to try to prevent the further spread of the current avian influenza (AI) virus outbreak.

In this article, you will learn more about the signs and symptoms of AI, some best practices to help prevent the spread of AI, and several recommended actions to take and resources to turn to if your flock tests positive for avian influenza.

Signs and symptoms of avian influenza in poultry

Avian influenza is a disease caused by influenza type-A viruses, which can infect both wild and domestic birds. Several factors can contribute to the spread of AI, such as migratory bird flight patterns, international trade and human-wild bird points of cross-contact. AI is more commonly detected in colder regions due to the resilience of the virus in low to freezing temperatures.

There are two clinical types of influenza virus in poultry: highly pathogenic (HP) and low-pathogenic (LP). The HP strains of bird flu can spread rapidly among poultry flocks and may cause multi-organ failure and sudden high mortality levels. The LP strains of bird flu form as asymptomatic infections, respiratory disease and/or drops in production.

Symptoms indicating the presence of avian flu in birds include:

  • Sudden death without any warning signs
  • Purple discoloration of the wattles, comb and legs
  • Swollen head, eyelids, comb, wattles and hocks
  • Soft-shelled or misshapen eggs
  • Decreased egg production
  • Lack of energy, appetite and coordination
  • Diarrhea
  • Nasal discharge
  • Coughing or sneezing
  • Ruffled feathers

How to help prevent avian influenza in poultry

Avian influenza viruses spread through direct contact with infected birds or through contaminated feed, water, equipment and clothing. Therefore, biosecurity is the first and most important method of prevention at the farm level.

For poultry producers to prevent the introduction of the virus to their flock, they are advised to:

1. Reduce wildlife attractants:

  • Remove standing water:
    • Grade your property to avoid the pooling of water.
    • Avoid walking or moving equipment near standing water used by wildlife.
  • Reduce food sources:
    • Do not feed wildlife.
    • Locate your feeding structures on a clean pad.
    • Have quick clean-ups for the feed storage area.
    • Mow frequently and remove fallen fruits.
  • Cover waste:
    • Do not pile used litter near barns.
    • Close dumpsters properly.
    • Keep carcasses covered.

2. Prevent wildlife access: 

Install exclusionary netting, screens and perch deterrents, like repellent gel or bird spikes.

3. Add wildlife deterrents: 

Move and replace scare devices frequently.

4. Keep birds away from areas frequented by wildfowl: 

Keep your birds indoors during high-risk times. If they cannot go indoors, make sure wild birds cannot access their feed and water sources.

5. Cover your run: 

Protect housed birds that may be able to have contact with wild birds, such as smallholding flocks in outdoor runs.

6. Maintain control over the access of people and equipment to poultry houses: 

If infected wild birds are in the area, reduce the movement of people, vehicles or equipment to and from areas where poultry are kept. Change your clothes before and after contact with your flock, and ensure that any visitors do the same.

7. Maintain sanitation of the property, poultry houses, equipment, vehicles and footwear: 

Disinfect regularly. For commercial poultry owners, clean and disinfect your housing at the end of a production cycle. Wash your hands thoroughly before and after contact with birds.

8. Avoid the introduction of birds of unknown disease status into the flock: 

Only acquire birds from sources that can verify that they are disease-free. Then, quarantine new birds for two weeks in separate quarters to ensure that they are healthy.

9. Report illnesses and bird deaths: 

Contact a vet if you have any concerns. Taking action quickly will help protect other flocks in the area if the disease is confirmed.

10. Appropriately dispose of manure and dead poultry:

Follow local guidelines regarding depopulation and disposal methods.

11. Maintain surveillance: 

At a minimum, follow local regulations regarding breeder flock monitoring and testing protocols.

Best practices to help prevent the spread of AI

Treatment with antiviral compounds is not approved or recommended for AI. It is best to have a monitoring system in place and to implement biosecurity measures as prevention against this virus.

Each country has a specific AI protocol in place, but in general, the policy is to humanely and safely cull the affected flock and enhance the biosecurity measures of the operation.

When formulating a culling policy, the World Organization for Animal Health (OIE) recommends:

  • The humane destruction of all infected and exposed animals.
  • The appropriate disposal of carcasses and all animal products.
  • Surveillance and tracing of potentially infected or exposed poultry.
  • Strict quarantine and controls on the movement of poultry and any at-risk vehicles.
  • The thorough decontamination of the infected premises. 
  • A period of at least 21 days before restocking.
  • Following all local and national guidelines.

Vaccination can be a powerful tool to support eradication programs if used in conjunction with other control methods. Using emergency vaccinations to decrease the transmission rate could provide an alternative to preemptive culling, reducing the susceptibility of healthy flocks at risk of contracting the virus.

According to the USDA Animal and Plant Health Inspection Service (APHIS), the typical steps to take when concerned with a potential avian influenza outbreak are:

Find: Detect, report and confirm the disease.

It is important to monitor each flock closely when an AI outbreak is present in the surrounding area. If signs of AI are detected, it is important to notify the USDA or your state veterinarian immediately. The USDA will then test samples to confirm if there is a positive case of AI and will provide more information regarding the specific strain and follow-up protocols.

Respond: Quarantine, depopulate, compensate and dispose.

If a location has tested positive for avian influenza, only authorized workers are allowed in and out of the facility. All movements of birds, poultry products and equipment are restricted to avoid cross-contamination between flocks. The birds are usually depopulated within 24 to 48 hours of testing positive and are disposed of shortly thereafter.

Recover: Clean, test and restock.

When the houses are empty, you must thoroughly clean and disinfect them, along with any equipment and other potentially affected areas. The house must then stay empty for an extended period of time, which varies depending on the species of bird. The USDA collects samples and tests to ensure that the AI virus has been eliminated, and a period of vacancy is required before new birds can be placed.

Did you know?

  • Although avian influenza A viruses do not typically infect people, rare cases of human infection with these viruses have been reported after unprotected contact with infected birds or surfaces contaminated with avian influenza viruses (CDC, 2017). 
  • H5N1 is a highly pathogenic avian influenza (HPAI) virus. It can be deadly for poultry and humans. The first human case occurred in 1997. Since November 2003, H5N1 has killed more than 50% of the people who have been infected with it (WHO, 2020).
  • H7N9 bird flu is rated by the Influenza Risk Assessment Tool as having the greatest potential to cause a pandemic, as well as potentially posing the most significant risk to severely impact public health if it were to achieve sustained human-to-human transmission.
  • Humans are usually infected through close contact with infected birds. Birds shed the influenza virus in their saliva, feces and mucous. Therefore, contact with bird droppings is also a possible transmission route.

References and Resources

USDA Avian Influenza Guidance Documents, USDA APHIS | Avian Influenza Guidance Documents

Centers for Disease Control and Prevention (2017), Avian Influenza A Virus Infections in Humans

USDA 2022 Confirmations of Highly Pathogenic Avian Influenza in Commercial and Backyard Flocks,

World Organization for Animal Health, Avian Influenza: OIE: World Organization for Animal Health

Watt Global Media, Breaking down U.S. avian flu cases by flock type | WATTPoultry (

Food and Agriculture Organization of the United Nations,



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