What is avian influenza?

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Minnesota Board of Animal Health Reportable Disease of the Month Header

March 2017

Avian Influenza

Veterinarian examining bird for avian influenza

What is it? Avian influenza is a viral disease affecting all species of birds. Similar to the flu, there are a variety of AI strains circulating in wild birds, usually wild waterfowl.  

There are two classifications of AI viruses: 

  • Low pathogenic (LPAI) commonly causes mild symptoms and birds can recover.
  • Highly pathogenic (HPAI) spreads rapidly through flocks killing most of the birds within 48 hours.

Minnesota has experienced both types of avian influenza in poultry flocks and continually monitors and tests flocks for avian influenza in cooperation with industry partners. While the viruses may cause marked illness and fatality in domestic poultry, waterfowl often show little to no signs of infection.

How is it transmitted? Avian influenza is spread easily from bird-to-bird through droppings or nasal discharge of an infected bird, which contaminates the birds’ environment. People can carry the virus on their shoes, clothes, equipment, and vehicles. Disease prevention and practicing routine, elevated and critical level biosecurity measures are the best way to stop disease transmission.

What are the clinical signs? Signs of low pathogenic avian influenza are typically mild, in many cases not visible and can go easily undetected.  It is similar to the common cold and can cause ruffled feathers, some respiratory signs, and a drop in egg production. Initial signs also include a quiet, non-active, flock and/or a drop in water and/or feed consumption. Highly pathogenic avian influenza leads to sudden and rapid death loss and moves through a flock more quickly; clinical signs include loss of appetite, lack of vocalization, a drop in egg production, coughing, swollen face, diarrhea and paralysis.

How is it diagnosed? Minnesota’s AI surveillance program has been in place for decades and we work with individual owners and the industry to actively look for the disease. Every commercial poultry flock in Minnesota is tested for influenza by the Board of Animal Health prior to going to market. All commercial poultry breeding flocks in Minnesota are tested for influenza monthly. Some smaller poultry flocks and live bird markets in Minnesota also participate in AI surveillance programs. Samples from poultry flocks are collected by Authorized Poultry Testing Agents (you can become certified during one of our annual testing agent trainings) and submitted to either the Minnesota Poultry Testing Laboratory in Willmar or the University of Minnesota’s Veterinary Diagnostic Laboratory in St. Paul.  Those labs test the samples submitted to identify evidence, or the presence, of an influenza virus.  If a test is positive, it is sent to the USDA’s National Veterinary Services Laboratory to be confirmed and officially classified. This type of surveillance is “active surveillance.” A second type of AI surveillance is called “diagnostic surveillance,” where birds are sent to a diagnostic laboratory and examined. If lesions on the bird are suggestive of AI, samples are collected, tested, and if positive, sent to the National Veterinary Services Laboratory.

Is there a risk to people? Avian influenza viruses do not usually infect humans or circulate among people. When they do, most infections are mild with mild respiratory symptoms and/or eye infections in some people working directly with infected birds. Some avian influenza viruses can cause serious illness or death. Influenza viruses can be unpredictable, which is why poultry workers and others who have close contact with AI infected birds should take caution, especially around HPAI. To date, the HPAI strains found in the United States have not been detected in humans. There is no evidence influenza is spread through food.

How can it be prevented? Practice biosecurity, which is a term used to describe the procedures followed by the poultry industry to contain or prevent the spread of disease in a poultry flock. These practices include isolation, sanitation and traffic control of people, animals and equipment. Avoid contact between wild and domestic birds, which includes avoiding feed or water placement that may attract waterfowl and other wild birds. Avoid on-farm traffic patterns that cross waterways, and wear appropriate footwear that can be cleaned and sanitized. In Minnesota, anyone who reasonably suspects AI is required to report AI suspect flocks to the Minnesota Board of Animal Health. The Board also works with backyard flocks to diagnose, control and prevent avian influenza.