Psittacine beak and feather disease
Encyclopedia
Psittacine beak and feather disease is a viral disease affecting all Old World
and New World
Parrots (Psittacini
, Hookbills). The virus belongs to the family Circoviridae. The virus attacks the feather follicles and the beak and claws-growing cells of the bird, causing progressive feather malformation and necrosis. In later stages of the disease, the feathers develop constrictions in feather shafts, cease development early until eventually all feather growth stops.
The beak and claws are affected in opposite direction – overgrowth, malformation and necrotic tissue development. Cracking and peeling of outer layers makes it possible for fungi and yeast
infections to take place and complicate matters even more. The necrosis of inner layers of the beak may cause it to break, at which point the bird will be unable to feed.
The disease also has a general immunosuppressive effect on the bird, clearing path for secondary systemic viral and bacterial infections which are usually the cause of death, not the PBFD virus itself. Previously unpublished data from Dr Ross Perry indicates that aspects of the immune system are working over-time, perhaps similar to an auto-immune disease in chronic PBFD
in Adelaide hills, South Australia in 1888.
The condition is more prevalent in widely occurring Australian species such as the Sulphur-crested Cockatoo
, Little Corella
and Galah
.
Over the years, Australian people seeing birds like this have thought their condition was caused by exclusive sunflower seed diet, which is often the main source of food for Australian cockatoos in captivity. Dr Ross Perry remembers being taught at Sydney University in 1969 that "a common feather loss disease of cockatoos is caused by too much sunflower seed in the diet". This is now known to be false.
The first case of chronic PBFD described by a vet was reported in a Control and Therapy article in 1972 for the University of Sydney by Dr Ross Perry, in which he described it as "Beak Rot in a Cockatoo" . Dr. Ross 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).
The virus causing the PBFD was first isolated and characterized by researchers Dr. David Pass of Murdoch University and Dr. Ross Perry from Sydney, with much work later continuing at the University of Georgia, USA, University of Sydney and Murdoch University in Perth, Western Australia. The virus was originally designated PCV – Psittacine Circovirus, but has since been renamed to "Beak and Feather Disease Virus", or BFDV. This is in part due to the research confirming that this virus is indeed the cause of the disease, and in part to avoid confusion with Porcine Circovirus, also shortened to PCV. It is circular in shape, belongs to the family Circoviridae
, measures 16 nm in diameter and consists of a single strand of DNA, between 1992 and 2018 nucleotides in length.
There are currently two BFDV tests available. A polymerase chain reaction
(PCR) test is very sensitive, and it can detect the virus in extremely small quantities, as long as the testing samples are reliable. The second test actually gives the viral count and the viral anti-body count (Hemagglutination
Assay/Hemagglutination Inhibition), but is not as sensitive as the PCR test.
The virus remains viable in the environment for many years and is resistant to most disinfectants.
) or other members of the flock (horizontal transmission
). The adult birds coming into contact with the virus usually (but not always) develop resistance to it, but the virus is retained in their body and, in most cases, is excreted in feces and feather debris for the rest of their life.
The immature immune system of young birds makes them very susceptible to the PBFD virus in their first few weeks of life. The virus may be transferred in crop
secretions, fresh or dried feces
and feather and skin particles.
. Due to the severe suppression of the immune system, multiple secondary viral and bacterial infections will develop, which will cause the death within two to four weeks.
The simplest way to confirm the diagnosis in the acute form of the disease is autopsy, because it progresses too quickly for the normal signs such as feather loss and beak deformity to appear.
The chronic form of disease takes place if the bird's immune system manages to mount some form of defense against the virus and the secondary infections. The characteristic feather symptoms need time to develop, and they only start appearing after the first moult
. In those species that have powder down, it will be affected immediately, as it is continually replenished.
Dr. Ross Perry FACVSc (Avian health) notes that the pattern of disease and the probability of remission varies markedly between species; with Budgerigar
s, African Lovebirds
, lories and lorikeets and Eclectus Parrots
presenting with acute to subacute disease being among those more likely to make a clinical recovery just on a "balanced diet", usually based on organic well-formulated pellets or crumbles supplemented with a little of a lot of fresh organic greens, vegetables and fruit, and given extra care for 1–2 moults.
On large Australian and New Guinea cockatoos, the very first sign of the chronic PBFD is the loss of powder down. On smaller, coloured cockatoos, the Eclectus
, King Parrot
, and many species of lories and lorikeets, first sign is feather discolouration. Coloured parrots seem to be less affected by the disease, often able to spontaneously recover. For the white cockatoo species, the prognosis is much worse.
In Australia, wild cockatoos have adapted very well to the urban environment and are a common sight in the suburbs. It is quite common for the flock to have one or more members visibly affected by the PBFD, without crest feathers, missing some flight and/or tail feathers, etc.
, due to the increasing international legal and illegal bird trade. Cases of PBFD have now been reported on all continents in at least 42 psittacine species, and this is likely to increase. At least 38 of 50 Australian native species are affected by PBFD, both captive and in the wild. In 2004, PBFD has been listed as a key threatening process by the Australian Commonwealth Government for the survival of five endangered species, including one of the few remaining species of migratory parrots, the Orange-bellied Parrot
(Neophema chrysogaster), of which only an estimated 60 mating pairs remain (as of 2006). An experimental killed virus vaccine has been produced, but the further development to refine it and make it commercially available is progressing slowly due to the lack of funding.
Unfortunately no therapies have been found yet. The management of the disease lies thus mostly in prevention. Every new bird that enters a pen with other birds should be quarantined first and be tested for PBFD virus. Birds which are known carriers should not be introduced into new pens, especially not if those contain young birds.
Old World
The Old World consists of those parts of the world known to classical antiquity and the European Middle Ages. It is used in the context of, and contrast with, the "New World" ....
and New World
New World
The New World is one of the names used for the Western Hemisphere, specifically America and sometimes Oceania . The term originated in the late 15th century, when America had been recently discovered by European explorers, expanding the geographical horizon of the people of the European middle...
Parrots (Psittacini
Psittacini
Tribus Psittacini consists of Afrotropical parrots; there are 8 species in 2 genera. Traditionally, the Vasa parrots are also included in this tribe, but that inclusion is not supported by molecular studies. Several of these species have subspecies including the African Grey Parrot which has 2...
, Hookbills). The virus belongs to the family Circoviridae. The virus attacks the feather follicles and the beak and claws-growing cells of the bird, causing progressive feather malformation and necrosis. In later stages of the disease, the feathers develop constrictions in feather shafts, cease development early until eventually all feather growth stops.
The beak and claws are affected in opposite direction – overgrowth, malformation and necrotic tissue development. Cracking and peeling of outer layers makes it possible for fungi and yeast
Yeast
Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...
infections to take place and complicate matters even more. The necrosis of inner layers of the beak may cause it to break, at which point the bird will be unable to feed.
The disease also has a general immunosuppressive effect on the bird, clearing path for secondary systemic viral and bacterial infections which are usually the cause of death, not the PBFD virus itself. Previously unpublished data from Dr Ross Perry indicates that aspects of the immune system are working over-time, perhaps similar to an auto-immune disease in chronic PBFD
The virus
The first report of featherless, dirty-looking birds in Australian bush was in 1907 by Edwin Ashby. He described the outbreak of PBFD in wild Red-rumped ParrotRed-rumped Parrot
The Red-rumped Parrot , also known as the Red-backed Parrot or Grass Parrot, is a common bird of south-eastern Australia, particularly in the Murray-Darling Basin.-Description:...
in Adelaide hills, South Australia in 1888.
The condition is more prevalent in widely occurring Australian species such as the Sulphur-crested Cockatoo
Sulphur-crested Cockatoo
The Sulphur-crested Cockatoo, Cacatua galerita, is a relatively large white cockatoo found in wooded habitats in Australia and New Guinea. They can be locally very numerous, leading to them sometimes being considered pests...
, Little Corella
Little Corella
The Little Corella, Cacatua sanguinea, also known as the Bare-eyed Cockatoo, is a white cockatoo native to Australia and southern New Guinea....
and Galah
Galah
The Galah , Eolophus roseicapilla, also known as the Rose-breasted Cockatoo, Galah Cockatoo, Roseate Cockatoo or Pink and Grey, is one of the most common and widespread cockatoos, and it can be found in open country in almost all parts of mainland Australia.It is endemic on the mainland and was...
.
Over the years, Australian people seeing birds like this have thought their condition was caused by exclusive sunflower seed diet, which is often the main source of food for Australian cockatoos in captivity. Dr Ross Perry remembers being taught at Sydney University in 1969 that "a common feather loss disease of cockatoos is caused by too much sunflower seed in the diet". This is now known to be false.
The first case of chronic PBFD described by a vet was reported in a Control and Therapy article in 1972 for the University of Sydney by Dr Ross Perry, in which he described it as "Beak Rot in a Cockatoo" . Dr. Ross 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).
The virus causing the PBFD was first isolated and characterized by researchers Dr. David Pass of Murdoch University and Dr. Ross Perry from Sydney, with much work later continuing at the University of Georgia, USA, University of Sydney and Murdoch University in Perth, Western Australia. The virus was originally designated PCV – Psittacine Circovirus, but has since been renamed to "Beak and Feather Disease Virus", or BFDV. This is in part due to the research confirming that this virus is indeed the cause of the disease, and in part to avoid confusion with Porcine Circovirus, also shortened to PCV. It is circular in shape, belongs to the family Circoviridae
Circoviridae
The Circoviridae are a family of viruses. These are small, relatively poorly-studied viruses, with circular, single-stranded DNA genomes of approximately one to four kilobases-Virology:...
, measures 16 nm in diameter and consists of a single strand of DNA, between 1992 and 2018 nucleotides in length.
There are currently two BFDV tests available. A polymerase chain reaction
Polymerase chain reaction
The polymerase chain reaction is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence....
(PCR) test is very sensitive, and it can detect the virus in extremely small quantities, as long as the testing samples are reliable. The second test actually gives the viral count and the viral anti-body count (Hemagglutination
Hemagglutination
Hemagglutination, or haemagglutination, is a specific form of agglutination that involves red blood cells . It has two common uses in the laboratory: blood typing and the quantification of virus dilutions.-Blood Typing:...
Assay/Hemagglutination Inhibition), but is not as sensitive as the PCR test.
The virus remains viable in the environment for many years and is resistant to most disinfectants.
Infection paths
The disease is usually acquired by the young nestlings from their parents (vertical transmissionVertical transmission
Vertical transmission, also known as mother-to-child transmission, is the transmission of an infection or other disease from mother to child immediately before and after birth during the perinatal period. A pathogen's transmissibility refers to its capacity for vertical transmission...
) or other members of the flock (horizontal transmission
Horizontal transmission
Horizontal transmission is the transmission of a bacterial, fungal, or viral infection between members of the same species that are not in a parent-child relationship....
). The adult birds coming into contact with the virus usually (but not always) develop resistance to it, but the virus is retained in their body and, in most cases, is excreted in feces and feather debris for the rest of their life.
The immature immune system of young birds makes them very susceptible to the PBFD virus in their first few weeks of life. The virus may be transferred in crop
Crop (anatomy)
A crop is a thin-walled expanded portion of the alimentary tract used for the storage of food prior to digestion that is found in many animals, including gastropods, earthworms, leeches, insects, birds, and even some dinosaurs.- Bees :Cropping is used by bees to temporarily store nectar of flowers...
secretions, fresh or dried feces
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...
and feather and skin particles.
Symptoms and signs
The acute form of the disease is manifested by lethargy, loss of appetite, vomiting and diarrheaDiarrhea
Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...
. Due to the severe suppression of the immune system, multiple secondary viral and bacterial infections will develop, which will cause the death within two to four weeks.
The simplest way to confirm the diagnosis in the acute form of the disease is autopsy, because it progresses too quickly for the normal signs such as feather loss and beak deformity to appear.
The chronic form of disease takes place if the bird's immune system manages to mount some form of defense against the virus and the secondary infections. The characteristic feather symptoms need time to develop, and they only start appearing after the first moult
Moult
In biology, moulting or molting , also known as sloughing, shedding, or for some species, ecdysis, is the manner in which an animal routinely casts off a part of its body , either at specific times of year, or at specific points in its life cycle.Moulting can involve the epidermis , pelage...
. In those species that have powder down, it will be affected immediately, as it is continually replenished.
Dr. Ross Perry FACVSc (Avian health) notes that the pattern of disease and the probability of remission varies markedly between species; with Budgerigar
Budgerigar
The Budgerigar , also known as Common Pet Parakeet or Shell Parakeet informally nicknamed the budgie, is a small, long-tailed, seed-eating parrot, and the only species in the Australian genus Melopsittacus...
s, African Lovebirds
Lovebird
A Lovebird is one of nine species of the genus Agapornis . They are a social and affectionate small parrot. Eight species are native to the African continent, while the Grey-headed Lovebird is native to Madagascar...
, lories and lorikeets and Eclectus Parrots
Eclectus
The parrot genus Eclectus consists of two species, the extant Eclectus Parrot and the extinct Oceanic Eclectus Parrot ....
presenting with acute to subacute disease being among those more likely to make a clinical recovery just on a "balanced diet", usually based on organic well-formulated pellets or crumbles supplemented with a little of a lot of fresh organic greens, vegetables and fruit, and given extra care for 1–2 moults.
On large Australian and New Guinea cockatoos, the very first sign of the chronic PBFD is the loss of powder down. On smaller, coloured cockatoos, the Eclectus
Eclectus
The parrot genus Eclectus consists of two species, the extant Eclectus Parrot and the extinct Oceanic Eclectus Parrot ....
, King Parrot
Australian King Parrot
The Australian King Parrot is endemic to eastern Australia. It is found in humid and heavily forested upland regions of the eastern portion of the continent, including eucalyptus wooded areas in and directly adjacent to subtropical and temperate rainforest...
, and many species of lories and lorikeets, first sign is feather discolouration. Coloured parrots seem to be less affected by the disease, often able to spontaneously recover. For the white cockatoo species, the prognosis is much worse.
In Australia, wild cockatoos have adapted very well to the urban environment and are a common sight in the suburbs. It is quite common for the flock to have one or more members visibly affected by the PBFD, without crest feathers, missing some flight and/or tail feathers, etc.
Threat
BFDV has the potential to become a major threat to all species of wild Parrots and to modern avicultureAviculture
Aviculture is the practice of keeping and breeding birds and the culture that forms around it. Aviculture is generally focused on not only the raising and breeding of birds, but also on preserving avian habitat, and public awareness campaigns....
, due to the increasing international legal and illegal bird trade. Cases of PBFD have now been reported on all continents in at least 42 psittacine species, and this is likely to increase. At least 38 of 50 Australian native species are affected by PBFD, both captive and in the wild. In 2004, PBFD has been listed as a key threatening process by the Australian Commonwealth Government for the survival of five endangered species, including one of the few remaining species of migratory parrots, the Orange-bellied Parrot
Orange-bellied Parrot
The Orange-bellied Parrot is a small broad-tailed parrot endemic to southern Australia, and one of only two species of parrot which migrate. The adult male is distinguished by its bright grass-green upperparts, yellow underparts and orange belly patch. The adult female and juvenile are duller...
(Neophema chrysogaster), of which only an estimated 60 mating pairs remain (as of 2006). An experimental killed virus vaccine has been produced, but the further development to refine it and make it commercially available is progressing slowly due to the lack of funding.
Treatment
There is currently no specific treatment for the virus. The experimental vaccine has been proven to provide protection against the virus, but is likely to accelerate the disease in parrots already infected with the virus. A new vaccine developed by Dr. Siwo de Kloet protects birds from the virus and does not endanger birds already infected with PBFD.Supportive care of affected pet birds
Firstly if a bird is infected and is being kept with several other birds, the bird should be quarantined and the pens disinfected. This to prevent spread through the other birds. Therapeutical interventions (by definition using pharmaceutical drugs) can only be limited to treating secondary infections (bacterial/fungal). The individual bird can sometimes recover, but it must be noted that this is rare. If only the feathers are affected and the bird suffers not of other signs, an acceptable life can exist. But if the bird's beak or nails get affected, most veterinarians will suggest to euthanase the animal. Dr Ross Perry often explores a holistic approach including the use of combinations of nutraceutical supplements to supporting the life and well-being of PBFD-affected pet birds and notes that the need for euthanasia because of suffering can sometimes be postponed for years .Unfortunately no therapies have been found yet. The management of the disease lies thus mostly in prevention. Every new bird that enters a pen with other birds should be quarantined first and be tested for PBFD virus. Birds which are known carriers should not be introduced into new pens, especially not if those contain young birds.
External links
- Manau PBFD – Website created by the owner of PBFD affected birds
- PBFD Home page, Murdoch University, Perth, Western Australia
- Infection by Psittacine circoviral (beak and feather) disease affecting endangered psittacine species and populations – key threatening process declaration
- Description of the First Case of Psittacine Beak and Feather Disease in Brazil, 1997
- Medical update: Important Diseases of Pet Birds
- Video of Oscar, Beak and Feather sufferer - YouTubeYouTubeYouTube is a video-sharing website, created by three former PayPal employees in February 2005, on which users can upload, view and share videos....