LPAI causes no or few clinical diseases in chickens and other domestic birds. Mostly it causes reduced egg production and poor growth rates. It may be controlled by quarantine, destruction of affected flocks or, in some circumstances, by vaccination. LPAI caused by H5 and H7 strains can mutate to HPAI, and so control of LPAI is of great concern.
HPAI causes severe illness and death among infected birds, both domestic poultry and wild birds. HPAI in wildfowl and domestic poultry must be reported to state and federal authorities. It is controlled by the quarantine and destruction of affected flocks where possible. An outbreak of HPAI is very obvious to the flock owner. Close to 100 percent of the birds in a flock may die in a short period of time.
Birds with HPAI show one or more of the following signs: