Psittacine beak and feather disease (PBFD) 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.
In the mid 1980s, researchers at the University of Georgia demonstrated that PBFD was caused by a previously undescribed virus, now designated PBFD virus 1. Several years ago, the same research group identified a variant of this virus (PBFD virus 2) that was originally recovered from lories.
To date, PBFD virus 2 has only been documented in lories. However, other birds may be susceptible to this or other variants. These variants may have a disease progression that is different from that described for PBFD virus 1.
Psittacine beak and feather disease has been documented in more than 40 species of captive and free-ranging Old World psittacine birds (cockatoos, African grey parrots, Eclectus parrots, lovebirds and budgerigars) as well as several species of New World Psittaciformes (Amazon parrots, macaws and pionus). Viruses related to the PBFD virus have been reported in pigeons, Senegal doves, canaries, finches, geese, southern black-backed gulls, ostriches, pigs, chickens and humans.
The PBFD virus is highly infectious and environmentally stable. However, most birds exposed to PBFD virus will have virus in their blood for a brief period (which can be detected using DNA probes), followed by an appropriate immune response that clears the virus before any recognizable feather abnormalities occur. Birds that survive this 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.
When the PBFD virus was characterized more than a decade ago, this virus was a common cause for the abnormal development of feathers. Because of improved education, improved aviary management and widespread use of diagnostic tests developed by researchers at the University of Georgia, today most feather abnormalities are caused by problems other than PBFD virus. The notable exception is that many lovebirds, budgerigars and lories with abnormally developing feathers will be diagnosed with PBFD virus.
What to Watch For
Birds may be infected with PBFD for months before developing feather abnormalities.
Birds that survive these rapid forms of the disease develop more chronic problems. Most pictures of featherless birds illustrate the chronic form of PBFD, which has progressed for years. The feather loss usually occurs equally in the feather tracts on each side of the body and normal feathers are progressively replaced with abnormally developed feathers during each successive molt. Suspicious changes include retention of feather sheaths, red-brown patches (represents accumulations of dying cells) within the developing feathers, fractures of the feather shaft and deformities or constrictions at the base of abnormal feathers.
Some birds die shortly after the first indication of malformed feathers; others may live for several years in a featherless state. While PBFD is reported most commonly in birds less than three years of age, the disease can also develop in older adult birds that have previously shown no signs of feather abnormalities.
The time period between exposure to PBFD virus and the development of feather abnormalities has been shown to vary among various species and among individuals in the same species. The minimum incubation period is 21 to 24 days. The incubation period in chicks with infections passed to them by the hen has been shown to vary from 32 to 80 days.