Females and chicks (pictured) seem particularly vulnerable.

 

Aspergillosis: A Critical Threat to Breeding Females

Researchers desperately hoped this would be a one-time outbreak. Treating the affected birds had required three full-time staff members at Auckland Zoo working for three months, with several birds needing ongoing care well beyond that period. Two remained in the hospital for over 250 days. A final bird, which had received a borderline diagnosis, was found dead the following year—possibly due to complications from treatment or a weakened immune system caused by the infection. The total cost of treating the outbreak exceeded $200,000.

Even more concerning was the devastating impact a recurrence of the disease could have on the female breeding population. Five percent of all breeding females had died, along with approximately ten percent of all chicks. Without treatment, an estimated ten to fifteen percent of the total population would have perished in a single season.

Given that Kākāpō breed only once every three to five years, significant research and funding were dedicated to preventing future Aspergillosis outbreaks. Fortunately, the outbreak had been contained to a single island (Whenua Hou), and birds on the other three Kākāpō islands remained unaffected.

However, when Kākāpō bred again in 2022, all eyes were on them. Would the disease return?

All eyes were on Whenua Hou for 2022

A Closer Look at the 2022 Kākāpō Breeding Season

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 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 in 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 weeks or months, often with limited symptoms. It can occur in both birds and mammals. However, Kākāpō lack both a diaphragm and an epiglottis (a flap of cartilage at the back of the throat), which is believed to make them more susceptible to inhaling microbes and particles.

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

Death from Aspergillosis can be a painful experience for Kākāpō

Aspergillosis Treatment Struggles 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. There is also no confirmation that the infection has ever been completely eliminated—two chicks died after being released into the wild, despite 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 the cause of death to be determined. However, it is possible that her weakened immune system never fully recovered from the damage it suffered.

The birds that survived 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 often needed, and the odds of survival 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 contribute to 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 favours birds that 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, the Kākāpō recovery team has exercised heightened vigilance 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 lowers 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 Kākāpō died from Aspergillosis in the 1960's

 Investigating the Potential Threat of Global Warming

However, the exact cause of these outbreaks has yet to be determined. Furthermore, it is 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 have 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 Kākāriki.

Auckland Zoo recently experienced an outbreak that affected all adult Kākāriki, although my understanding is that 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 Kākāriki suffered an outbreak of Aspergillosis.

Research Efforts and Strategies to Combat Aspergillosis in Kākāpō

 

Currently, research is being undertaken to explore soil and air samples from Kākāpō burrows, Kākāriki 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 is 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 has been suggested that Stewart Island Kākāpō are so inbred that the impact of breeding these siblings together would produce fewer harmful alleles than those 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 unanswered questions surrounding Aspergillosis. It is 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 have 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 is impacting breeding females now but not in the past.

Thankfully, a significant amount of funding has been allocated towards finding these answers. The sooner we can understand what is at the heart of this weakened immune response in Kākāpō, the safer the species as a whole will be.

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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