Researchers identify gyrovirus threatening critically endangered penguin chicks

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A quarter of the mainland’s yellow-eyed penguin or hoiho chicks will die from respiratory disease by 2021 as researchers search for a cure.
Photo: Janelle Wierenga

The probable cause of a disease that has led to mass deaths among critically endangered hoiho chicks has been discovered, in hopes it can eventually be prevented.

About a quarter of the mainland’s yellow-eyed penguin chicks died from the respiratory disease during the breeding season from November to December 2021.

The multi-agency research group identified a new gyrovirus likely responsible for the deadly disease after autopsying 43 dead chicks.

The group was led by two University of Otago researchers, including virologist Dr Jemma Geoghegan.

Three Otago populations of hoiho are monitored annually and newly hatched chicks are monitored and weighed every two to three days.

Chicks with respiratory symptoms or weight loss are immediately transferred to Dunedin Wildlife Hospital for treatment.

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About 137 wild hoiho chicks were hospitalized, with 31 showing signs of respiratory disease within the first week.

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Hoiho are threatened.
Photo: Trust yellow-eyed penguin

Twenty-seven of them died within 24 hours of showing symptoms, one survived five days with intensive veterinary care, and three were treated and returned to the nest.

Tissue samples were taken from the 43 dead chicks that revealed a “highly abundant gyrovirus,” said Dr. Geoghegan.

“We collected tissues from the chicks that died of respiratory distress syndrome and used next-generation sequencing technology to identify any pathogens present,” she said.

“This is the same technology that Chinese scientists used to determine that a new coronavirus caused a respiratory disease in humans, which was later named SARS-CoV-2, of course.

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“We have identified a new gyrovirus that appears to be abundant in samples from the sick chicks. The virus is related to other gyroviruses that cause disease in other birds, including chickens.

“Related viruses that affect chickens have vaccines to prevent them, so a vaccine could be a possibility one day, but there’s a lot more work to be done.”

The research group also developed a PCR test to determine the presence of the virus in the future.

The first suspected case was back in 2015, but the disease was first diagnosed in 2019.

There was an ongoing investigation to try to understand where and when the virus showed up, she said.

University of Otago virologist Jemma Geoghegan.

Dr. Jemma Geoghegan
Photo: University of Otago

“In 2020 and 2021, the number of chick deaths from this disease quadrupled and increased fivefold, compared to 2019, with a mortality rate of over 90 percent. Chicks usually succumbed to the disease within the first 10 days of life.” Dr. Geoghegan said.

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The northern hoiho population occupying mainland New Zealand and Stewart Island has experienced a 75 percent decline over the past three decades.

“They are feared to become extinct on mainland Aotearoa in the coming decades, with infectious diseases a major contributor to their decline.

“Therefore, this joint effort is extremely important so that we can ensure the survival of this taonga.”

The research group includes Dunedin Wildlife Hospital, the Yellow-Eyed Penguin Trust, the Department of Conservation, the Ministry for Primary Industries and the Universities of Otago and Massey.

The Morris Animal Foundation funded the research.