Psittacine Beak and Feather Disease
The psittacine beak and feather disease ( PBFD ;. English for "feather and beak disease of parrots") is a highly contagious, incurable and often fatal outgoing viral infection in parrots (psittacids, parakeets and parrots). It is the most common viral disease in parrots in Germany and now affects not only large parrots, but also budgies and other small parrot birds. PBFD is also common among wild parrots. The first description of the circovirus was based on psittacids from the southern Pacific region and has now been identified in many other species. For the Cape Parrot , which is one of the long-winged parrots and is considered the most threatened African large parrot species, this disease represents one of the population-threatening factors in addition to the loss of habitat.
Cause and development of the disease
The causative agent of the PBFD is the Beak and Feather disease virus (BFDV) from the virus family Circoviridae . These are small, 12–21 nm large, non-enveloped DNA viruses . Circoviruses are very contagious. They have a high tenacity in the environment and are only safely inactivated by a few disinfectants (e.g. glutaraldehyde ) .
Different species of the circoviruses are also found in other bird orders ( chicken , pigeon , canary , corvidae ), but they are specific and not transferable between the orders, so a budgie cannot become infected with the circovirus of a pigeon.
The infection is done by oral uptake of the virus or an airborne droplet infection. Due to the high tenacity, indirect transmission through inanimate vectors (cage furniture, clothing, claw scissors, etc.) is also possible. The incubation period , i.e. the period from infection to actual disease, can stretch on for months or even years. Therefore, when buying animals, there is a very high risk of the disease being introduced into a bird house.
After infection, the virus spreads in the blood ( viraemia ) and the viruses settle in the organs of the lymphatic system , in the feather follicles and the skin, as well as in the esophagus and goiter . In these organs, cells die off ( necrosis ). Infected birds excrete the virus through goiter secretion, faeces, and through skin and feathers.
proof
PBFD is usually determined by a blood test or freshly pulled feathers with the polymerase chain reaction through detection of virus DNA . In a few special laboratories, this is also possible using fecal samples.
Clinical picture
Nestlings and often also young birds show a peracute course without the typical symptoms in older animals. With them, the infection with diarrhea and exhaustion is usually fatal after a short illness without any changes in feather or beak.
The disease progresses more slowly in older animals. Damage to the feather follicles leads to failure of coverts and flight feathers, to brittle or constricted feather shafts and to persistent feather sheaths (these are tube-like sheaths around the developing feathers, which normally tear when the feathers grow out, causing the feather to unfold). The springs are easy to pull out and may show changes in color. The changes in the plumage grow stronger from moult to moult. The remaining horn formations ( claw , beak ) lead to excessive growth with a soft, brittle horn.
The infestation of the lymphatic organs ( thymus , bursa fabricii ) leads to a reduction in the number of white blood cells ( leukopenia ) and thus to a reduced immune defense, so that the infected birds often suffer from secondary infections. The immune deficiency usually leads to death 6 to 24 months after the outbreak of the disease.
In adult birds the disease can also be completely symptom-free. These animals are dangerous pathogen excretors for stocks.
In the typical course, the diagnosis can be made based on the clinical picture. A polyomavirus infection , in particular , can be excluded from the differential diagnosis , whereby both diseases can occur simultaneously. Pathogens can be detected using PCR on plucked, freshly growing feathers .
Combat
A therapy of PBFD is not possible. The young birds usually die before treatment can begin. In older animals one can try to keep the bacterial and mycotic ( aspergillosis ) secondary diseases under control and to support the immune system through optimal housing conditions, optimal feeding and the avoidance of stress.
Since the therapy is not very promising, prophylaxis is of particular importance. The most important measures are a quarantine of at least 90 days for new purchases with a check-up, strict isolation of sick animals and regular disinfection of rooms, aviaries or cages for stocks.
literature
- M. Pees: Circovirus infection in parrots and parakeets - a disease of increasing importance. Small animal in detail 7 (3) / 2003, pp. 33–36.
Individual evidence
- ^ Dieter Hoppe , Peter Welcke: Langflügelpapageien , Ulmer Verlag, Stuttgart 2006, ISBN 3-8001-4786-6 , p. 27
