The orange-bellied parrot (Neophema chrysogaster), one of the world's most critically endangered birds, could lose its bid at survival as a virus threatens its vitally important captive breeding program.

The unidentified stomach virus that has struck the program causes the birds to lose their feathers and weakens their immune systems, Shane Radial, a veterinary professor with Charles Sturt University, told the Australian Broadcasting Co. Because the captive parrots live in close proximity to one another, "infections just find it easier to spread from one bird to another," Radial said.

About 160 to 170 orange-bellied parrots live under the auspices of three captive breeding programs: two located on Australia's mainland at Healesville Sanctuary and Adelaide Zoo; one at Taroona on the island of Tasmania. Radial did not identify in which facility the disease is present. Another 50 of the birds exist in the wild.

The nature of the virus has not been established. An unidentified scientist posting on the ProMED mail program for the International Society for Infectious Diseases theorized that it could be avian influenza or proventricular dilatation disease, which hampers food digestion.

The orange-bellied parrot was listed in 2006 as critically endangered under Australia's Environment Protection and Biodiversity Conservation Act. Once common in Tasmania and Australia, the species has declined in the past 100 years as its coastal salt marsh habitat was destroyed for agricultural purposes. Other threats include the pet trade; the introduction of invasive weeds, some of which are toxic to the birds; and the introduction of non-native predators such as foxes and feral cats. According to the Australian government's national recovery plan for the species, the captive breeding program was previously set back by outbreaks of psittacine circoviral disease in 1991 and what may have been a herpes virus in 2005 and 2006, which killed 43 birds. It is not yet known if the current outbreak has killed any of the birds or just weakened them.

Photo via Wikipedia