NSW Scientific Committee - final determination
The Scientific Committee has found that:
1. Psittacine Circoviral (beak and feather) Disease (PCD) affects parrots and their allies (psittacines) and is often fatal. It is caused by a relatively simple virus that infects and kills the cells of the feather and beak, as well as cells of the immune system, leaving birds vulnerable to bacterial and other infections (Murdoch University 1997).
2. PCD has been identified in more than 38 species of captive and wild indigenous psittacine birds in Australia, however all psittacine species are considered susceptible to infection (EA 2001).
3. No other faunal species or groups are known to be susceptible to PCD (Murdoch University 1997). Similar diseases found in pigeons and doves are caused by similar but antigenically different circoviruses (Bassami et al. 1998).
4. Most parrots that succumb to PCD are less than two years old, however all age groups are considered susceptible (Murdoch University 1997). Acute and chronic forms of the disease are recognised. The majority of chronically affected birds do not recover from the disease. Partial or complete recovery from acute PCD can occur spontaneously in many species (Raidal 1995).
5. PCD does not necessarily represent a major threat to species unless there are few populations or limited numbers of birds that are susceptible to catastrophic events. However, in circumstances where bird populations have been dramatically reduced, such as in an endangered species, the disease has the potential to cause catastrophic losses (EA 2001).
6. Characteristics which may increase a species' vulnerability to catastrophic epidemics of this disease include a small and declining number of breeding birds, and few subpopulations (EA 2001). The following species and population listed as threatened in NSW are known to have a high infection rate of PCD that may already be adversely affecting them:
Orange-bellied Parrot Neophema chrysogaster (one subpopulation of approximately 180 breeding birds (Garnett and Crowley 2000); implementation of the captive breeding component of the national breeding plan has been severely impacted by PCD (EA 2001);
the population of Gang Gang Cockatoos Callocephalon fimbriatum from the Hornsby and Ku-ring-gai local government councils which has a high incidence of PCD (J Hardy, pers. comm.).
7. Threatened species considered to have a high potential for being adversely impacted by PCD are:
Coxen's Fig Parrot Cyclopsitta diophthalma coxeni (four subpopulations of approximately 100 breeding birds (Garnett and Crowley 2000); captive breeding for species recovery may increase their vulnerability to PCD);
Swift Parrot Lathamus discolor (one subpopulation of approximately 2000 birds (Garnett and Crowley 2000); PCD confirmed in wild birds from NSW).
8. The PCD virus is one of the most resistant viruses capable of causing disease. It can remain present in the environment and viable in nest boxes and hollows for many years, and may result in long-term contamination of nesting sites (EA 2001). Transfer of the virus is likely to occur through the sequential use of nest sites (Raidal 1995). The virus can potentially be transferred into wild populations of susceptible parrots by release of birds that have been infected through captive breeding or care.
9. There is no evidence that PCD is a threat to the survival of psittacine taxa that are not endangered (EA 2001).
10. Psittacine Circoviral (beak and feather) Disease affecting endangered psittacine species is listed under the Environment Protection and Biodiversity Conservation Act 1999 as a Key Threatening Process.
In view of the above the Scientific Committee is of the opinion that Infection by Psittacine Circoviral (beak and feather) Disease affecting endangered psittacine species and populations is eligible to be listed as a key threatening processes, as it adversely affects two or more threatened species or populations.
Proposed Gazettal date: 06/12/02
Exhibition period: 06/12/02 - 24/01/03
References:
Bassami, M. R., Berryman, D., Wilcox, G. E. and Raidal, S. R. 1998. Psittacine beak and feather disease virus nucleotide sequence analysis and its relationship to porcine circovirus, plant circoviruses, and chicken anaemia virus. Virology. 249: 453 - 459.
EA. 2001. Psittacine Circoviral (beak and feather) Disease. Key Threatening Processes webpage: accessed: July 2001.
Garnett, S. T. and Crowley, G. M. 2000. The action plan for Australian birds 2000. (Environment Australia: Canberra.)
Murdoch University. 1997. PBFD. Psittacine beak and feather disease webpage: accessed: July 2001.
Raidal, S. R. 1995. Viral skin diseases of birds. Seminars in avian and exotic pet medicine. 4(2): 72 - 82.