Jack Hanna, also known as "Jungle Jack," became one of the most notable animal experts in the U.S. beginning in the 1980s as the director of the Columbus Zoo and Aquarium

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Jack Hanna
Jack Hanna
| Credit: Columbus Zoo and Aquarium

Jack Hanna, who gained national recognition for his love of animals as the director of the Columbus Zoo and Aquarium, has been diagnosed with dementia, now thought to be Alzheimer's, his family announced on Wednesday.

Hanna's daughters, Kathaleen, Suzanne, and Julie, announced their 74-year-old father's diagnosis in a letter shared on social media Wednesday by the Columbus Zoo, where Hanna, also known as "Jungle Jack," served as director from 1978 to 1992. He officially retired from his conservation duties late last year.

"His condition has progressed much faster in the last few months than any of us could have anticipated," Hanna's daughters shared in the letter. "Sadly, Dad is no longer able to participate in public life as he used to, where people all over the world watched, learned, and laughed alongside him."

Hanna, who has been married to Suzi Egli since 1968, became a beloved public figure during his years as the director of the Columbus Zoo. During that time, he enjoyed frequent media appearances — often joined by exotic animals — on talk shows, including The Tonight Show Starring Johnny Carson, Good Morning America, Late Night with David Letterman, and Maury.

The Late Show with David Letterman Jack Hanna
Jack Hanna
| Credit: John Paul Filo/CBS via Getty

In May 2018, Hanna received the Tom Mankiewicz Leadership Award for his work in conservation at the Los Angeles Zoo's annual Beastly Ball.

"A passion for wildlife conservation and education has been at the core of who our dad is and everything he has accomplished with the help of so many," Hanna's daughters wrote in their letter. "He has spent his life connecting people and wildlife because he has always believed that having people see and experience animals is key to engaging them in more impactful conservation efforts."

They continued, "Even though Dad is no longer able to travel and work in the same way, we know that his infectious enthusiasm has touched many hearts and will continue to be his legacy."

Jack Hanna
Jack Hanna
| Credit: Steve Fenn /Walt Disney Television via Getty

The letter also revealed that Julie is battling "life-long continued challenges" from her childhood leukemia and is currently recovering from major surgery. The sisters' asked for privacy for their family, which they noted "is ironic given Dad's love of interacting with people."

"We are grateful that the many hearts he's touched over the years are with him during this journey, which gives us strength."

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KIDS ARE PEOPLE TOO Jack Hanna
Jack Hanna
| Credit: Walt Disney Television via Getty
Jack Hanna
Credit: Columbus Zoo and Aquarium

Along with sharing the letter and photos of Hanna on Facebook, the Columbus Zoo said they were "saddened" by news of Hanna's diagnosis and Julie's health complications. The zoo added that the Safari Golf Club, The Wilds, and Zoombezi Bay also support the Hanna family during this difficult time.

"His legacy will be ever-present in our work as we continue to fulfill our organization's mission to lead and inspire by connecting people and wildlife," the zoo said of Hanna.