When a bird develops the illness, the disease is characterized by feather abnormalities, feather dystrophy and ultimately, death.
PBFD can affect birds of any age, but is more commonly seen in young birds from 0-3 years. Although many older birds can suddenly turn up positive for the virus, even though they had been clinically normal most of their lives. Especially disconcerting is the fact that this disease is EXTREMELY contagious. Viral particles are airborne. Dried feces & feather dust can adhere to clothing, nesting material, feeding formula, feeding utensils, nets, bird carriers, toys, & a myriad of other vehicles of possible transmission.
Obvious symptoms of PBFD are feather-dystrophy, possible bald patches on the head (this may exclude certain breeding-pairs, in which the male bird may pluck the female's head-feathers out.) If your bird has feathers missing elsewhere such as the chest, it's likely that the bird has plucked out it's own feathers, but PBFD should be ruled out before one can make such an assessment. Other signs are missing primary wing feathers and/or tail feathers, ragged looking or half-developed feathers, powdery feather-sheaths, or sheaths that don't dissapear within a few weeks. Infected birds will eventually lose most or all feathers and become extremely ill. Then the bird will die a very painful death, usually from secondary infection, or possibly failure of one or more internal organs.
*Many birds (including young birds) that carry the disease will show NO SYMPTOMS. This means that even healthy looking birds should be tested because they still may be carrying the disease. They may initially test negative. There have been current discussions by breeders who have experienced this disease. They have explained that birds can test negative, possibly for several months. They explained that after certain previously diagnosed "negative" birds had been through some traumatic ordeal (such as shipping) the birds show a positive result. Stress is thought to "pop" the disease. This will cause the dormant virus to begin the process of shedding itself. They have assessed that stressful times are the best times to test your birds. For new acquisitions, right after shipping would be the ideal time to test them. On established birds, you may want to set up a temporary nestbox, which can cause stress, or take the bird for a bumpy ride in your car.
A negative test result does not prove that a bird is free of the virus because an incubation period of up to 4 weeks may be neccessary before the virus can be detected in the blood. Birds who test negative should be tested subsequently at 30 days after possible exposure, and if negative, retested again at 60 days.
Author; L. Wagner-Chambers