Psittacine Circovirus (PCD), previously known as Psittacine Beak & Feather Disease (PBFD).
Following a trip to Canberra in August 2002 to attend a meeting for the development of a Threat Abatement Plan, I feel that it is timely to pass on some information regarding the current status of the disease we all know as Psittacine Beak and Feather disease. ( PBFD)
The disease has been renamed and is now currently referred to as PCD or Psittacine Circovirus Disease. Psittacine Circovirus (PCD) has been identified as one of the smallest viruses in terms of size. This presents problems in relation to trying to eradicate or control the spread of the virus within the Psittacine bird population, both in the wild and in aviculture. The virus currently infects most of the parrot and cockatoo species within Australia and many others outside Australia. In America, where the disease gets lots of publicity, it appears to be confined to the pet population of birds and has not been reported in the wild. In Australia this is very different.
We are faced with having most common and many endangered Psittacines in the wild recorded as having the virus. It appears that while these birds are not under undue stress, feeding on appropriate, balanced nutritional food, and are in "stable" conditions the disease does not cause too many birds to progress into the critical stages of the disease. The disease can be tolerated at a certain level within the bird and will allow the bird to live a reasonable life, participating in all the normal daily activities. These levels are different for each different species and the level at which Sulphur Crested Cockatoos function with the disease may be very different from the level at which Crimson Rosellas can function for instance.
If, however, the conditions are changed for birds carrying the disease, either by pressure from habitat loss, artificial feeding, or some change in the conditions under which they are stable, the virus increases in concentration within their body and they are then pushed into the next more critical stage of the disease and will either die directly from the disease or from an associated infection due to the decreased immunity as a result of the virus. This is the stage at which most of the birds entering the rehabilitation system appear to be.
It is important to appreciate that different species of birds react to the disease in different ways. Some species of birds have affected beak and feathers, others have only the feathers affected, others only have the immune system compromised. Within each species there is a variation also that can lead to some birds staying apparently fit and well yet be infected and spreading the disease.
Different species and individual birds also react to certain levels of the disease in different ways. Some will tolerate a given level well whilst others will die from the same level of exposure to the disease, and others will be pushed to the next stage of the disease eventually leading to death.
There is much talk regarding the ability of birds to recover from the disease. In birds such as the Rainbow Lorikeet for example, they may visibly recover from the effects of that episode of the disease but in reality they continue to have the virus present in their body, particularly in the liver. These birds excrete the virus from their body in their faeces, blood, saliva and feather dust. It is often at a much higher rate than normal and it is this extremely high level of the virus that other birds come into contact with that causes many of them to then move into the next stage of the disease or even die from it.
Effectively, whilst we may not be able to stop the disease in the wild populations of birds, by not sending birds back to the wild, known to be shedding the virus at higher rates than are manageable by most birds, we can allow it to be managed by the birds in a pseudo-natural way themselves.
If, on the other hand we continue to expose all birds to higher than normal concentrations by releasing rehabilitated birds shedding very high concentrations of PCD, we risk epidemics, cross infection to other species, and a reduction in the overall ability of the birds left in the wild to manage the disease if levels are continually being raised.
What is needed for this disease to be able to be managed by the birds themselves, is no further high levels to be forced on them by birds being released shedding abnormally high levels of the virus. To do this, Rainbow Lorikeets and Sulphur Crested cockatoos or any bird known to have the disease should not be released. The simple way to do this is to have birds that are known to have the potential for carrying the virus tested before they are released.
It should also be understood that most of the birds that have been cared for in the wildlife network are going to often decline and return to a active stage of the disease and die after release due to stress or other factors that brought them into the rehab system in the first place. If Wildlife carers see themselves as being conservation aware, then surely the population in the wild MUST be a priority. To intentionally jeopardize them by releasing birds known to be shedding abnormally high levels of a disease, (NOT just PCD), exposing other species to this disease, allowing it to potentially develop in other species, and to progress the disease in stable populations of infected birds is grossly irresponsible.
It is also interesting to note that two scientists who are active in research on the disease, potential development of a vaccination and management of wild populations with the disease, both recommend that birds should not be released unless tested and known to be free of the disease.
Much is argued about this disease amongst wildlife carers and indeed vets, however, if we are to keep up with the changes that are being made and new information that is being discovered about this disease, it is imperative that we keep an open mind and make sure that information is passed on to ensure that all carers are kept up to date with the current practises and thinking on the diseases, not just the information from America where NO research is done on wild populations.
Feathers
& Foxtrot 