Psittacine Beak and Feather disease was first described in various species of cockatoos in the early 1970s. The disease was characterized by abnormal feather development and loss, beak deformities and eventual death. So far, the disease has been documented in more than 40 species of birds. The PBFD virus is highly infectious and environmentally stable. Birds that survive infection (typically without developing feather abnormalities) can be viewed as naturally vaccinated. Genetic material (DNA) from this virus can be detected in a bird's blood as soon as 2 days after natural exposure to the virus, and weeks to months before an infected bird will develop feather abnormalities.
For more information, read Psittacine Beak and Feather Disease