Mwelu (“Lu”), a 34-year-old chimpanzee at Zoo Knoxville, is recovering well after undergoing a groundbreaking spinal surgery to remove a tumor—an operation believed to be the first documented procedure of its kind performed on a chimpanzee.

Lu, a chimpanzee at Zoo Knoxville

The delicate surgery was conducted on Friday, September 19, 2025, at the University of Tennessee College of Veterinary Medicine, through a collaboration between Dr. Talisha Moore, a veterinary neurologist, and Dr. James A. Killeffer, a human neurologist at the University of Tennessee Medical Center.

Zookeepers had noticed that Lu had recently begun showing signs of weakness in his hind legs. Dr. Julie Sheldon and Dr. Andrew Cushing of the University of Tennessee College of Veterinary Medicine examined Lu. An MRI revealed a tumor pressing against his spinal cord, leaving surgery as the most viable option to preserve his mobility and quality of life.

“This was an incredibly rare case,” said Dr. Moore. “Chimps are far more like humans than they are like dogs or cats, so we knew we needed a unique surgical approach. Partnering with Dr. Killeffer allowed us to combine expertise from both veterinary and human medicine to give Lu the best chance at recovery.”

Following a CT scan to ensure there were no signs of cancer elsewhere in his body, Lu was cleared for surgery. The operation required meticulous planning and a coordinated team of anesthesiologists, veterinary staff, and surgical technicians.

Dr. Killeffer, who specializes in human neurosurgery, emphasized the significance of the operation: “Not only have I not heard of this procedure being done in a chimpanzee, I couldn’t find any record of it in the literature. We were able to remove the vast majority of the tumor, relieve pressure on the spinal cord, and give him a path to healing.”

Bill Street, Zoo Knoxville’s President and CEO, praised the extraordinary effort:

“I could not be more proud of the many caregivers and medical experts who came together for this historic procedure. Their dedication has given Lu the opportunity for a longer, fuller life while also paving the way for other chimpanzees who may benefit from this groundbreaking work in the future.”

Zoo officials report that Lu is recovering in a special quarantine space, where he is being closely observed while he heals. He has already shown signs of improved movement and is enjoying the extra care and attention from his dedicated keepers.

“The exceptional medical care demonstrated in this surgery highlights our dedication to collaboration,” said Dr. Paul Plummer, Dean of the University of Tennessee College of Veterinary Medicine. “Our partnerships with Zoo Knoxville and the University of Tennessee Medical Center are essential. By leveraging our expert staff and cutting-edge facilities, we advance veterinary medicine and elevate the standard of care daily. This achievement reflects the commitment of everyone involved.”

We will continue to monitor his health and share updates as we learn more about his condition.

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