Avian Influenza

The World Organization for Animal Health (OIE) lists Highly Pathogenic Avian Influenza (H.P.A.I.) as one of only two poultry diseases targeted for emergency control measures.   Outbreaks have resulted in millions of birds lost, including a 1983-84 outbreak in Pennsylvania that resulted in the deaths of approximately 17 million birds.  Typically A.I. is of mild pathogenicity, with many infections going undiagnosed.  However cases have been documented of mild cases adapting into H.P.A.I., especially when the disease is able to circle back through populations.  This disease can result in very high mortality, especially in turkeys. H.P.A.I. has historically been called fowl plague, though this name is no longer in clinical use. 



  • Chickens 
  • Ducks
  • Geese
  • Other wild birds
  • Pheasants
  • Seabirds
  • Turkeys (most severe)

Where:  Worldwide, but most outbreaks are of the mild form which can go undiagnosed.

When:  Any age.

Why:  Orthomyxovirus Type A influenza viruses (many variations)


  • Readily transmitted by air.
  • Spread by nearly anything that comes in contact with the disease. 
  • Spreads via bird-to-bird contact.  


            Symptoms - Mildly Pathogenic form

  • Diarrhea        
  • Lethargy         
  • Low mortality ·       
  • Respiratory distress 

            Symptoms - Highly Pathogenic form:

  •  Blue or purple discoloring of the skin
  •  Death - sudden with no other obvious signs
  • Dehydration
  • Facial swelling
  • High rate of morbidity. 
  • Respiratory distress


            Highly Pathogenic form:       None is effective.   This is a reportable disease in all states  which requires quarantine and depopulation. 


Vaccine:  Yes, but it is of minimal value due to the large number of strains with A.I. 

Coop Care

  • Practice good biosecurity
  • Maintain overall good health to increase resistance
  • Quarantine all birds with severe respiratory problems until testing can be performed to confirm the cause. 


Also Known As

  •  A.I.
  • Avian Flu
  • Bird Flu
  • European Fowl Pest
  • Fowl Plague
  •  Influenza

Affects:  Most commonly the respiratory system; digestive and nervous systems are occasionally affected. 

Clinical Diagnosis:  For the Highly pathogenic form, few signs are observed prior to death.   Depression or a semi-comatose state may be observed.   Additional diagnosis by laboratory testing of the virus.

Diseases with similar symptoms: 

            Highly Pathogenic form:

  • Heat exhaustion
  • Infectious Laryngotracheitis
  • Exotic Newcastle Disease
  • Peracute septicemic Fowl Cholera
  • Severe water deprivation.

            Mildly Pathogenic form:

  • Chlamydiosis
  • CRD
  • Infectious Bronchitis
  • Infectious Coryza
  • Infectious Laryngotracheitis
  •  Newcastle Disease
  • Respiratory Fowl Cholera

Duration of symptoms:  Mildly pathogenic form: 10-14 days; Highly pathogenic form: 1-3 days

Incubation:  Several hours to 3 days 

Morbidity:  Up to 100%. 

Mortality:  Up to 100%, but often low.  Mortality can increase very rapidly. 

Transmission to people:  The severe form may cause infections in humans, but infection between different species is very rare.    These cases usually result in single or few cases, as adaptation between species slows the transmission. 






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A righteous man cares about his animal's health...

Proverbs 12:10a