Bird - Circovirus Infection

General information

This disease was first described in Australian cockatoos in the early 1970s. It is commonly called Psittacine Beak and Feather Disease (PBFD) describing the chronic form of the disease with abnormalities of beak and feathers. However there is also an acute form causing immunodeficiency and death in young Grey parrots. Therefore the syndrome is more correctly named Circovirus infection after the causative organism.

How do birds become infected with the virus?

The virus is readily spread in feather dust, faeces and (possibly) other secretions. These are ingested allowing infection to develop.

What are the signs of circovirus infection?

In the acute form birds will be presented at less than 24 weeks old. They are usually fluffed and unwell. A blood count reveals anaemia and a lack of white blood cells. They normally die within a few days from a secondary infection.

In the chronic form birds may take months to years before showing any clinical signs. They start with the appearance of unusual feathers – funny shapes, unusual colours, complete loss, etc. They normally appear to be otherwise well. The signs progress with each moult and the bird becomes progressively more bald. In the latter stages the beak becomes affected (cracking, etc) and birds die through debility and/or secondary infection.

In either case it is believed that infection must occur before the bursa of fabricius (see below) has resorbed (it disappears by a few months old). Infected adult birds (without a bursa) normally manage to fight off infection.

This virus is also a cause of French moult in budgerigars and may be carried by normal budgies.

How is the disease diagnosed?

A skin and feather biopsy can be used to eliminate other causes of abnormal skin and feathers. It is not 100% diagnostic for beak and feather disease but can be strongly suggestive of it. A blood test using a DNA probe is the best way to diagnose the disease especially in acute cases. DNA probes may also be performed on bone marrow (especially acute cases) or feather pulp of affected feathers. In acute cases diagnosis is often achieved at post-mortem examination – in these cases a sample of Bursa of Fabricius (an immune organ near the cloaca) is essential.

How do I know if my bird is infected?

Birds can be screened for the virus using a simple blood test. New birds should be screened for the disease; if the bird is infected, it probably won't show clinical signs for quite a while and the owner needs to be informed of this. Additionally, many new birds are sold with a health warranty. A bird testing positive should be covered under the warranty and the owner may decide to return it. Any owner purchasing a new bird would have the resident bird and new bird tested before bringing the new bird into the household. It should also be remembered when birds are susceptible. If an otherwise healthy adult bird is found to be positive then it is worth isolating it and re-testing in 90 days; it is possible for it to be transient infection and may be negative at a later date.

Similarly a negative blood test may not mean that the bird is free of disease. Often the virus will 'hide' in the feather follicles, bursa or bone marrow resulting in a negative blood test.

How is beak and feather disease treated?

Unfortunately, there is no treatment for the disease and it is usually fatal. Supportive care can be given and can extend the life of the bird for quite some time. Infected birds should be kept separate from non infected birds as the disease is easily transmitted. It is also worth keeping budgerigars separate from larger parrots.