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.
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)
Symptoms - Mildly Pathogenic form
Symptoms - Highly Pathogenic form:
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.
Also Known As:
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:
Mildly Pathogenic form:
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.