Three years ago, most New Zealanders would have never heard of Aspergillosis. Yet, all that changed in April 2019. New Zealand's most critically endangered bird, the much-adored Kākāpō, was about to make the disease famous. Kākāpō are nocturnal flightless parrots that live up to a hundred years old, breed once every three to five years, and exist only on a handful of islands off the coast of New Zealand. Beset by threats, they are the world's most intensively managed bird. So few remain that they're all individually named, and their lineages back to a small population of founders are all known.

During a critical breeding season, a young female named Huhana stopped feeding her chicks. Rangers monitoring her were worried when she ceased all activity and movement. Within hours, they observed she seemed to be struggling to breathe. They quickly intervened, ferrying her to a veterinary clinic for treatment. However, within days, she succumbed to a mystery illness and died.

As one of fewer than a hundred female Kākāpō in the world, her loss was keenly felt. Yet, that was just the beginning. Within days, other birds began to sicken, including both nesting females and chicks. More than twenty birds were rushed to Auckland Zoo, representing more than fifteen percent of the living Kākāpō population. Nine of them would die within weeks.

The cause was revealed to be Aspergillosis, a rare respiratory disease seen only a handful of times prior in Kākāpō and never in breeding birds. The outbreak left scientists scrambling to identify the cause and what it might mean for the Kākāpō population.

Females and chicks (pictured) seem particularly vulnerable.

Critical Impact on Breeding Females: Examining the Toll of Aspergillosis

Researchers desperately hoped that this would be a one-time outbreak. It had taken three full-time staff members at Auckland Zoo three months to treat the majority of the birds, and several required ongoing treatment far beyond this date. Two needed to remain in the hospital for upwards of 250 days. A final bird with a borderline diagnosis was discovered dead the following year, possibly due to complications after treatment or a weakened immune system from the infection. The total cost of treating the infection came out to be over $200,000. 

Of even greater concern was the devastating impact a recurrence of the disease could have on the female breeding population. Five percent of the breeding females in existence had died, plus around ten percent of all chicks. Without treatment, ten to fifteen percent of the population would have died in a single season.

Given that Kākāpō only breed every three to five years, a significant amount of research and funding was committed to preventing future Aspergillosis outbreaks. Thankfully, the outbreak had been contained to a single island (Whenua Hou), and birds across the other three Kākāpō islands were unaffected. Yet all eyes were on Kākāpō in 2022 when they bred again. Would the disease strike again?

All eyes were on Whenau Hou for 2022

A Closer Look at the 2022 Kākāpō Breeding Season: Triumphs and Tragedies

The 2022 Kākāpō breeding season kicked off with a bang. Record numbers of Kākāpō were breeding, and estimates suggested that for the first time in a century, the Kākāpō population might exceed 250 birds.

Then tragedy struck. This time on Anchor Island, hundreds of kilometers away from Whenua Hou. A young female named Jemma was observed to be struggling to feed her chicks. Worrying, but not uncommon for a first-time mother with a large clutch. As a precaution, she was taken away from her nest for a CT scan. The results were horrifying; she was so riddled with Aspergillosis that she was deemed to be drowning in an internal pool of her own fluid. Within hours, her condition had declined, and she passed away.

Researchers returned to Anchor only to find the genetically critical female, Ra, dead (though later research indicated she may have died of an accident). Then another female, Roha, stopped feeding her chicks and was rushed off the island for treatment. Other chicks and birds would follow. Rapid treatment minimized casualties, but still, several more birds died.

The outbreak left researchers stumped. How could flightless birds with no connection to each other, hundreds of kilometers apart, suddenly start dying of the same disease? To understand that, we need to understand what Aspergillosis is.

Several genetically valuable birds died.

Understanding Aspergillosis: Causes, Symptoms, and Diagnostic Challenges

Aspergillosis is a fungal infection caused by microscopic mold spores that gradually build up over a period of weeks or months with limited symptoms. It can occur in both birds and mammals. However, Kākāpō lack both a diaphragm and epiglottis (a flap of cartilage at the back of the throat), which is believed to make them more susceptible to inhaling microbes/particles.

Typically, in Kākāpō, the first indication of aspergillosis involves the bird ceasing to feed itself or chicks, followed shortly afterward by listlessness, organ failure, and death. An elevated white blood count may be an indication of the infection, and CT scans are often used to determine the spread of advanced cases. However, the most accurate testing comes from endoscopy, which involves the insertion of a tube down the mouth of a sedated bird into the airways of the sick bird. Samples are then collected for analysis and testing.

Death can be a painful experience

Treatment Struggles: The High Cost and Complexities of Combating Aspergillosis in Kākāpō

Treatment is complicated; at a certain point, there is no hope. Jemma and Huhana were brought into care, but it was too late to save them. Nor is there total confirmation that the infection has ever been eliminated; two chicks died after being released into the wild, both having been medically given the all-clear. The female Ihi was a borderline case who recovered quickly and was returned to the wild with minimal problems. Two years later, she was discovered dead, too badly decomposed for her cause of death to be clear. However, it may be that her weakened immune system never fully recovered from the damage it suffered.

The birds that did survive required both oral antifungals and antibiotics. One chick even required surgery to attempt to remove an abscess in her airway, which was slowly causing her to choke to death. Sadly, this chick did not survive. Once surgery is required, there is little hope of saving the bird. Moreover, multiple surgeries are required to save the bird, and the odds of them recovering from even one, given their weakened immune system, are low.

Treatment for sick birds is complicated

Factors Contributing to Aspergillosis: Genetics, Diet, and Climate Considerations

Genetic factors may also result in birds succumbing to Aspergillosis. Ra and Jemma were both chicks produced by artificial insemination, and Huhana was hand-reared, as were Hoki and Ihi. It may be that Aspergillosis naturally favors birds who wouldn’t have survived without human intervention in the first place.

There might be a dietary component to Aspergillosis; birds lacking vitamin A may be more susceptible, and there could be some transmission via food sources. In 2005, Male Kākāpō Gunner was found dead from Aspergillosis. It was believed he inhaled mold spores from his supplementary food during feed outs, and since then, heightened vigilance has been observed by the Kākāpō recovery team regarding the storage of supplementary foods.

Another possibility is that the hotter summer in 2019 played a part. The breeding season was a ‘mega mast year’ where hot, dusty, dry conditions allowed the majority of birds to breed earlier and longer than ever before, leading to many double clutches. Kākāpō breeding typically happens over two months, but in the 2019 season, there was a five-month gap between the first and last mating. This extended season may have weakened the immune systems of the birds and created the perfect conditions for spores to be inhaled. This could have been facilitated by increased mycotoxin production, suppressing the birds' immunity.

Certainly, healthy birds might be exposed to Aspergillosis and not become sick; however, excessive exposure could result in even healthy birds falling ill. It might be that the stress of raising chicks or prolonged breeding seasons could lower Kākāpō immune systems. There is a precedent for this: a Kākāpō living at Mount Bruce in the 1960s died from stress-related Aspergillosis after struggling to adapt from life in the wild to an aviary.

A Captive Kakapo died from Aspergillosis in the 1960's

Aspergillosis Transmission: Investigating the Potential Threat of Global Warming

However, the exact cause of these outbreaks has yet to be determined. Furthermore, it’s not currently known if the disease is transmissible between birds. Some research into stitchbirds suggests it may be, whereas other studies have ruled it out. One researcher I’ve spoken to believes that the outbreaks have arisen independently of each other and that, for some reason, there has been increased exposure to these mold spores. Though that has yet to be proven.

Whatever the cause, the point of transmission of grave concern is the possibility that outbreaks may be caused by global warming. This could explain why outbreaks have occurred in two consecutive breeding seasons across two different islands. Aspergillosis is not just a Kākāpō disease; it impacts Hihi (or Stitchbirds), Kiwi, and Kakariki.

Auckland Zoo recently experienced an outbreak that affected all adult Kakariki, although my understanding is none died. Sadly, Wellington Zoo lost eight young Rowi to Aspergillosis in 2013. Proportionally, the disease has taken its biggest toll on Kākāpō, but it remains a threat to much of our Taonga (native treasures).

Auckland Zoo Kakariki suffered an Outbreak of Aspergillosis

Towards a Solution: Research Efforts and Strategies to Combat Aspergillosis in Kākāpō

Currently, research is being undertaken to explore soil and air samples from Kākāpō burrows, Kakariki nest boxes, and Kiwi house enclosures to assess how altering microbial communities might reduce the growth of Aspergillosis. Another option might be to explore ways to bolster Kākāpō immunity during breeding seasons. 

The key may also lie with the Fiordland male, Richard Henry, and his adult son, Gulliver. All known Kākāpō are descended from an isolated and relatively inbred population that survived on Stewart Island for thousands of years. These birds suffer from a high degree of inbreeding, infertility, and low genetic fitness. It’s possible they also have weakened immune systems due to these factors. Richard Henry was the only mainland Kākāpō to ever breed; he produced three chicks, Kuia, Gulliver, and Sinbad, before passing away in 2010.

Interestingly, of these birds, Gulliver carries rare MHC disease-resistant alleles found in no other bird. Moreover, across the Fiordland birds, about a fifth of all alleles are unique to them. So genetically different are mainland Kākāpō that Dr. Andrew Digby has suggested it may be better to breed Fiordland birds with each other to keep the strength of these alleles in concentrated bloodlines. It’s been suggested that Stewart Island Kākāpō are so inbred that the impact of breeding these siblings together would produce less harmful alleles than the ones that already exist in the population. It could be that Gulliver and his offspring carry the alleles needed for Kākāpō as a species to overcome immune issues like Aspergillosis.

There remain a multitude of unknown questions surrounding Aspergillosis. It’s unclear why the southernmost island of Kākāpō suffered the most severe outbreak. Surely, if it were linked to rising temperatures, birds in the far North would have succumbed first? Furthermore, hihi populations on Little Barrier have struggled as a result of Aspergillosis, yet Kākāpō has remained unaffected. Why the infection has been recorded on two southern islands, and not the third, is not clear. Nor is it clear why it's impacting breeding females now, but not in the past.

Thankfully, a multitude of funding has been pushed toward finding these answers. The sooner we can understand what’s at the heart of this weakened immune response from Kākāpō, the safer the species as a whole will be.

Enjoy this style of investigative journalism?

Support us by purchasing from our online store which allows us to devote more time to stories like this.

Special Thanks to Gemma England for her help with this article. Thanks to Brodie Philip for his updates that made me aware of the most recent outbreak. Thanks to Dr Andrew Digby for the use of his photos