Psittacine beak and feather disease

Psittacine beak and feather disease (PBFD) is a viral disease affecting all Old World and New World parrots. The causative virus—beak and feather disease virus (BFDV)—belongs to the taxonomic genus Circovirus, family Circoviridae. It attacks the feather follicles and the beak and claw matrices of the bird, causing progressive feather, claw and beak malformation and necrosis. In later stages of the disease, feather shaft constriction occurs, hampering development until eventually all feather growth stops. It occurs in an acutely fatal form and a chronic form. Cracking and peeling of the outer layers of the claws and beak make tissues vulnerable to secondary infection. Because the virus also affects the thymus and Bursa of Fabricius, slowing lymphocyte production, immunosuppression occurs and the bird becomes more vulnerable to secondary infections. Beak fractures and necrosis of the hard palate can prevent the bird from eating. Psittacine beak and feather disease was first described in the early 1980s and has become recognised as the dominant viral pathogen of psittacine birds worldwide. In wild red-rumped grass parakeets (Psephotus haematonotus), a case of feather loss syndrome that was highly suggestive of PBFD was first recorded in South Australia in 1907. The virus causing PBFD was initially designated as psittacine circovirus but has since been renamed beak and feather disease virus (BFDV). The condition is more prevalent in widely occurring Australian species such as the sulphur-crested cockatoo, little corella and galah. The first case of chronic PBFD was reported in a Control and Therapy article in 1972 for the University of Sydney by Ross Perry, in which he described it as "beak rot in a cockatoo". Dr. Perry subsequently studied the disease and wrote extensively about its clinical features in a range of psittacine birds in a long article in which he named the disease "psittacine beak and feather disease syndrome" (PBFDS). This soon became known as psittacine beak and feather disease (PBFD).