Zoo officials say they made the "difficult" decision to euthanize Houdini, a 14-month-old male Gentoo penguin, on Sunday.
They say Houdini had been sick for almost a month and a necropsy confirmed he had severe aspergillosis.
That's a fungal infection that affects the bird's respiratory system, and officials say it is a common cause of death for penguins in captivity.
Head of veterinary services Dr. Sandie Black says the massive flooding in June may have increased the risk for the disease as dampness helps the fungi grow and spread.
Eduardo, a Humboldt penguin, died Oct. 13 from aspergillosis, as did Asa, a King penguin, in February.
Black says penguins are especially sensitive to acquiring the infection, with increased disease noted when the spore levels become concentrated and/or the birds' immune systems are depressed, as when they moult.
"As a precaution, all penguins have been proactively treated for aspergillosis, as they were in the days immediately following the flood in June.”
Black also says they may be dealing with a drug-resistant fungi.
"Some of our penguins are not responding to current therapy as we would expect. Further testing is underway to determine if this is the case.
"In addition, we are in discussions with other penguin specialists around the world to learn from their experiences, and may invite other experts to review our facilities and risk factors," she said in a news release.
Black said the fungi pose little risk to people.
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