The beak may also be involved in the disease process. It may changed from a dull black to a glossy appearance. It may grow abnormally long and develop splits and cracks which break and peel. It often becomes difficult for the bird to eat because the beaks becomes very painful. The disease is considered to be fatal.
Some birds die shortly after showing signs of PBFD while others live months to years.
PBFD is spread by inhalation or ingestion of virus particles. Feather dust has been found to contain a large amount of virus. The virus has also been found in crop secretions and in fecal material. The virus may also be ingested as a result of preening. The incubation period of variable among species and the age at which the bird is exposed.