Circovirus / Psittacine (PBFD) is a tiny virus that can cause devastating disease, including damage to feathers, beaks and the immune system, especially in cockatoos and parrots, where it is called Psittacine Beak and Feather Disease (PBFD). Strains of the virus can also cause disease in canaries, pigeons and other bird species. The disease is not catchy to humans or other animals.
The virus is secreted in droppings and feather dust of beak and feather disease infected birds; it survives well in the environment and is resistant to many disinfectants. Most birds are infected through contact with the circo virus when they are young but new research suggests that, in rare cases, infected hens may transmit the virus vertically i.e. to their eggs when they are forming and then to their chicks.
Signs and progress of PBFD will vary depending on what species is affected and when the bird acquires the infection in relation to their moult cycle. Young birds are more susceptible to beak and feather infection than older birds, especially in Australia where the virus is widespread and most young birds, especially those that are wild caught, will have had some exposure to the virus and have either developed immunity or contracted the disease early in life. The virus affects keratin (beak and feather protein) formation and may suppress the bird’s immune system.
Circovirus in Different Species
Cockatoos are typically exposed to the virus as juveniles if their parents are circo-virus carriers (ie shedding the virus but not showing signs of disease) or there is virus in the nesting hollow or if they mix with other birds that have been exposed to the virus (e.g. when trapped for the pet trade). However, most often they don’t begin to show typical signs of PBFD until their adult moult which generally starts the autumn after they fledge. When old feathers moult out the new feathers replacing them may be deformed and stunted.
The powder down feathers (on the hips) produce a talcum powder-like substance as their tips disintegrate. This spreads over the plumage to keep it clean. With PBFD these feathers are often the first to show abnormalities as they grow continuously. Without powder down, the plumage becomes dirty. Other feathers (e.g. the crest, contour or wing and tail feathers) may follow. Erosion, overgrowth and breakage of the beak is also common (‘beak rot’). Claws may overgrow and the beak and feet may appear black rather than their normal greyish colour.
At Melbourne bird Vet have had birds who have had advanced PBFD and have had hardly a feather on them but have managed to survive decades with the disease. More commonly, because the virus suppresses the immune system, birds become ill with other diseases and die or owners elect euthanasia because quality of life is poor and/or they are concerned that the bird may pass on the virus to owner birds.
Budgies commonly lose their flight feathers only instead of the total feather losses seen in parrots. These birds are commonly called “runners” or “bullets” as they are still quite active and will run around the bottom of the cage.
Lorikeets, like budgies may just lose their wing and tail feather. If this happens in juvenile birds it is not uncommon for feathers to regrow the following year and for the bird to go on to be normal. Unfortunately these birds usually still shed the virus even if they appear normal and pose a risk to other birds. In other cases lorikeets may lose feathers all over their body, these birds rarely regrow feathers but may go on to live many years.
Parrots generally. In addition the typical signs described above for cockatoos, budgies and lorikeets, parrots generally can show a range of signs associated with the disease. There may be any degree of feather loss from a mild mottled appearance to severe loss; feathers may or may not appear stunted or deformed or new feathers formed after infection may be coloured differently (e.g. from green to yellow or white feathers may appear). Beaks may, or may not be eroded, overgrown or damaged.
Canaries. A specific strain of circovirus different to the ones that cause disease in parrots can cause death and ill health in nestling canaries. It usually shows up at age 10-20 days and is one of the causes of ‘Black Spot’ in canaries, so called because an enlarged liver or gall bladder can be seen as a black spot on the abdomen of affected birds.
Pigeons may be affected with a specific strain of circovirus that typically does not cause feather damage but damages the immune system and leaves the birds more susceptible to other infections.
Advanced cases of circovirus, particularly in parrots and cockatoos can often be suspected based on history and clinical appearance. For confirmation Bird Vet Melbourne forwards diagnostic tests (usually PCR) on blood or feathers to an external Laboratory.
Treatment and Prevention
Unfortunately there is no consistently effective treatment for circovirus and birds with the beak and feather birds continuing to shed the virus and pose a risk if other birds come into contact with them.
Over the years trials on many drugs have been undertaken (including e.g. interferon trial done at bird vet Melbourne) but none of these therapies have consistently reversed disease in birds already showing signs of the illness. In many cases, with good care, birds with circovirus can live comfortable lives for many years, e.g. a cockatoo at our clinic that had had circovirus as a youngster and had lost almost all of his feathers lived more than 40 years. More often, birds show signs of secondary illnesses and/or owners decide that the quality of life is poor and elect to have them euthanased.
Beak and feather disease can be contracted through direct contact with infected or carrier birds or contact with the virus which may remain viable in the environment for many months or possibly years. Care should be taken to keep bird species that can contract circovirus, especially young birds whose immune systems are not fully developed, away from birds known to have circovirus or the environment where they have lived (e.g. old nest boxes). Circovirus is resistant to many disinfectants, we recommend, through cleaning followed by the use of F10. A vaccine for circovirus has been made but is not currently available.