Former Columbus Zoo Director Emeritus Jack Hanna has been diagnosed with dementia.

The popular wildlife advocate's three daughters announced the news in a lengthy statement shared to Twitter on Wednesday.

"Today we reach out to share some personal Hanna Family news. Doctors have diagnosed our dad, Jack Hanna, with dementia, now believed to be Alzheimer's disease. His condition has progressed much faster in the last few months than any of us could have anticipated. 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," Kathaleen, Suzanne and Julie Hanna said in a joint statement.

Hanna served as director of the Columbus Zoo from 1978 to 1992. He then took over the role as its spokesperson, a role he retired from in 2020.

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In addition to being a notable figure in the state, Hanna also appeared on several television programs as a wildlife correspondent, bringing people and animals together. He starred in "Animal Adventures," "Into the Wild," and "Wild Countdown" and was known for his several appearances over the years on morning talk shows and late-night TV, including "The Late Show with David Letterman," "Larry King Live," "The Ellen DeGeneres Show," "Hollywood Squares," and "The Maury Show."

"The Columbus Zoo and Aquarium has been a major part of our lives since we moved to Central Ohio as young girls in 1978. From day one, Dad advocated for improved wildlife habitats and focused on connecting the community with animals," his daughters continue in their statement.

Hanna's daughters also recalled one of his famous quotes -- "You have to touch the heart to teach the mind" -- as a reminder that despite the diagnosis, his enthusiasm for wildlife conservation and education is still very much present.

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Former Director Emeritus of the Columbus Zoo Jack Hanna has been diagnosed with dementia, his three daughters announced on Wednesday. (Michael Tullberg/Getty Images)

Kathaleen, Suzanne and Julie also note that he's no longer able to travel and work as he did previously. They also recalled his weekly television appearances as bringing great joy to viewers around the world.

"Dad engaged with millions of households through his media appearances and weekly television programs...This allowed him to bring an unparalleled level of awareness to the importance of global conservation given the unrelenting pressures on the natural environment. To say that we are abundantly proud to be his daughters is an understatement," his daughters said.

Hanna's wife Suzi also remains by his side. Married for 53 years, his daughters say the matriarch continues to "be his rock." Suzi also has been helping the couple's daughter Julie in her own physical challenges, noting that in addition to having life-long complications from childhood leukemia, she recently underwent a "major surgery."

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"Dad loves the Columbus Zoo and The Wilds and has great appreciation for hundreds of employees and volunteeres who work extremely hard each day to care for the animals and ensure an incredible experience for the families who visit. We share his dedication to the Central Ohio community and will continue to support the Columbus Zoo and conservation efforts around the world," the statement continues.

Hanna's daughters also note that although he's not at work, he "still wears his khakis at home" and his "great sense of humor continues to shine through."

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"To keep everyone safe in light of COVID-19 restrictions, we are asking for privacy, which 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 him strength," the family statement concludes.