Fungal disease is killing New Zealand's rare kākāpō

Tuesday, 21 May 2019

DOC Ranger Jake Osborne with five male kākāpō chicks, between 63 and 73 days old, which are being hand-reared in Invercargill.

First it was crusty bum, now the endangered kākāpō is falling victim to a fungal disease called aspergillosis, with five dead over the last month and another not expected to live.

Thirteen of the flightless parrots - the heaviest in the world - are being treated in Auckland Zoo for the disease, which is very difficult to treat.

Despite the setback, this year's breeding season has been the most successful to date, with 73 chicks born. The adult kākāpō population is now 143, revised down from 144 due to an old male called Merty being taken off the population list as he has not been seen for nearly five years so is assumed dead.

The bird that is expected to die is an adult, which will bring adult numbers down to 142.

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Associate Zoology Professor Bruce Robertson from Otago University said a likely reason for the deaths was that the birds had low immunity systems because they were so inbred.

Ruapeke was born in 2014 and is still alive.

'It could well be that it's got something to do with the low levels of genetic diversity that we've found. The island ones, which is pretty much all of the current population, are basically inbred.

'That could result in them having less genetic diversity in the immunity genes, which allow them to fight off bugs.'

Department of Conservation science advisor Dr Andrew Digby said his concern was that the disease had affected some of the 'founder' birds. These were ones discovered on Stewart Island in 1977, and which had gone on to found the current population.

Of the 85 found on Stewart Island, only 61 lived long enough to be transferred to safety on Little Barrier and Whenua Hou (Codfish) islands in the early 1990s. Robertson said there were between 35-40 of the founders remaining.

Espy 1B made the news earlier this month when it had brain surgery at Wildbase Hospital at Massey University, an unrelated problem to the one suffered by the birds being treated at Auckland Zoo.

DOC operations manager for the kākāpō programme, Deidre Vercoe, said six of the 13 birds being treated at Auckland Zoo had aspergillosis confirmed by CT scan, and the other birds would be scanned as soon as possible. One of the birds had been at the zoo for some time with congenital issues and did not have a clear-cut case of aspergillosis.

Aspergillus spores were common in the environment and usually do not cause disease, but birds with low immunity could succumb to respiratory disease if exposed to high doses of spores.

'We've very rarely seen this in kākāpō before and we are unsure of the cause of any underlying impact on the birds' immunity. We are working with an extended vet team to explore possibilities, but it may be as simple as general immunity being compromised through normal nesting/fledging activity, along with a bad season for aspergillus spores,' Vercoe said.

Robertson said the disease not only infected the birds' lungs, but entered into air sacs which are located throughout the body.

Associate Professor Dr Bruce Robertson of Otago University, a kākāpō expert, says the birds are very inbred, which may have lowered their immunity against disease.

'It grows relatively slowly but once it's taken hold then it gets into the air sacs, so then once it's right throughout the body, it's right throughout the breathing system.'

Several years ago scientists investigated the problem of 'crusty bum' that some kākāpō were suffering from. Robertson said 'the jury's still out on whether it was genetics or environmental. It could have a genetic component'.

Other diseases also offer a threat to the bird. The 'parrot and feather' disease is in the rosella population on the mainland as well as the kakariki.

Vercoe said DOC had increased monitoring of a number of chicks on the island.

'While it's important we celebrate successes, in nature we can't control everything and need to be prepared when things go wrong.'