Introduction to PBFD in birds
As with most viral conditions, PBFD has two forms; acute (sometimes known as peracute) and chronic. Acute PBFD is the form most commonly found in young birds and usually is fatal, causing multiple organ failure. The first signs in a young bird are not usually related to either the feathers or the beak, but may present as depression, regurgitation, loss of appetite and diarrhoea. Only after these symptoms have been noted does involvement of beak and feathers begin, with the youngster showing signs of lesions on the feathers, which may break and bleed. This is very painful for the bird and in view of the low level of survival when the disease presents like this, most vets will recommend euthanasia.
Early Signs of PBFD
The chronic form of PBFD presents more commonly in older birds and in this case the feather symptoms are the first to appear. Bands appear on the powder down feather, which will break off and bleed. These feathers will drop out leaving bare skin and they will not regrow. Later, lesions will appear on the beak, leaving sunken patches, or the beak may grow long and oddly shaped. Alongside all of this, the bird may develop liver lesions and this will quickly result in death. The actual cause of death in most cases, usually within 6 months of the onset of the symptoms, is normally a secondary infection, caused by the bird having compromised immunity and also bare lesions where fungal and opportunistic bacterial infections can take hold.
Again, euthanasia is usually recommended, as the bird will be feeling wretched and at this point in the development of the disease, there is little hope of cure. This must be decided on a case by case basis as a lone bird, which is a companion bird or a beloved pet can sometimes be made comfortable enough with warmth and nutritional back-up to live the rest of its life, which will in any case be a maximum of two years.
Diagnosis of Psittacine Beak and Feather Disease
As with so many other viral infections, PBFD presents in such as way in the early stages that it can be mistaken for other conditions ranging from nutritional issues to other viruses, such as polyomavirus. This means that the disease is usually advanced by the time it shows the typical feather and beak lesions which are diagnostic in themselves. Blood tests are available, and swabs taken from a bird actively shedding the virus will show positive, but negative blood tests are so unreliable that they should be discounted if other symptoms are present.
Psittacine Beak and Feather Disease is also known as Parrot Circovirus but most commonly by the initials PBFD. It was first identified in Australia in 1975; it is endemic in wild birds in Australia. The virus which causes it is not cross-species and so it cannot be passed to humans, but it is very similar to other viruses found in mammals, for example pigs, and even some plant viruses, most notably one which affects bananas. Another avian type of circovirus affects doves and other birds. Any psittacine can be affected by PBFD, but from literature and experience it appears that those most susceptible are cockatoos, African Greys, lovebirds, ringneck parakeets and macaws. This is not an exhaustive list, so all owners of birds from the parrot family should be vigilant.
Treatment of birds with PBFD
There is no treatment beyond making the bird as comfortable as is possible if not euthanized. Some birds contract a very mild version of the viral infection and go on to form a natural immunity, so it is important not to react too quickly and make an irreversible decision. Scrupulous cleanliness is essential, but the virus – incidentally, one of the smallest disease causing organisms ever discovered – is not affected by any of the commonly used (or safe) forms of disinfection, not even those used in hospital operating theatres and so it is not sufficient to merely swab areas.
Cleanliness the Key
All feather dust, faeces and any other debris in the environment must be removed on a very regular basis; if it is allowed to accumulate, draughts will stir up the dried virus and this will then be inhaled by the birds in the aviary. The disease can then lie dormant for quite some time within the bird, but more importantly the virus can live outside the host for many months in dried faeces, skin cells or other debris and will reactivate when breathed in or ingested.
Prevention of PBFD
As always when caring for any caged animal, cleanliness of the environment is paramount. Only buying birds from reputable dealers will also go a long way to preventing cases of PBFD in a collection, but quarantining new birds, even from such a dealer, is always a good idea. Estimates vary as to how long the quarantine should be but 30 days is considered an absolute minimum. A vaccine of killed virus is available and it should be given to young birds as soon as possible, at around 2 weeks old, in case any of the adult birds are carriers. This should be followed up four weeks later and then boosters should be given annually.
A very few young birds may have the disease sub-clinically; these animals then go on to develop a natural immunity which it is believed they are able to pass on to their broods, although this has not be proved in laboratory conditions.
Care when using the Vaccine
Care should be taken however with using this vaccine, because of the asymptomatic stage of PBFD. If a bird has the disease sub-clinically, a vaccination can kick-start it into the full blown condition. This is not to say that the vaccination will ‘give’ the bird, PBFD, merely that a bird which may have lived symptom free for a few more years will now manifest the disease and may die more quickly. So care should be taken when deciding to vaccinate adult birds; this problem does not apply to juveniles, who have not yet had a chance to develop the asymptomatic chronic form.