Hogle Zoo and University of Utah Health have collaborated to diagnose and treat one of the zoo’s California sea lions, Diego, which fell ill in September 2024. Through a combination of anesthesiology, veterinary science, and advanced imaging, the team identified the cause of the sea lion’s reduced activity as advanced spinal disease and determined an appropriate treatment to alleviate his symptoms.
Worrying signs
Each breeding season between May and August, male sea lions experience rut—a period of heightened hormonal activity marked by vocalizations, displays of dominance, and territorial behaviors. Shortly after rut season ended in September, Diego’s care team observed changes in his behavior. Diego, typically lively and robust, became less mobile, vocalized more than usual, and showed a decreased appetite. These concerning signs prompted swift action from the zoo’s animal care and health teams.
Diagnosing Diego
Hogle Zoo enlisted pinniped anesthesia expert James Bailey, DVM, to try to diagnose Diego. On October 5, 2024, Bailey and a team of keepers, veterinarians, and health partners from U of U Health anesthetized Diego and performed bloodwork and an abdominal ultrasound in the sea lions’ indoor habitat.
The initial results came back normal, which ruled out several potential concerns but left the cause of Diego’s symptoms unknown.
Diego is an incredibly special individual that we, the Rocky Shores team, have had the privilege to care for since he arrived here at UHZ in 2017. Initial exam results alleviated some concerns, but we knew we needed more information. Our veterinary and animal care teams were ready to meet the challenge of figuring out the logistics of how to get Diego the best possible diagnostic care to allow us to properly address the health concerns we were seeing.
The next step? Getting a 650-pound sea lion to a CT scanner. With his care team by his side, Diego was carefully moved to the U of U Health radiology department. Under anesthesia, Diego’s vital functions were manually supported by his team, who delivered breaths through a large oxygen tank during the transfer.
Hogle Zoo’s medical and husbandry team often perform innovative diagnostics and therapies to give the animals the very best care possible, but taking a 650-pound sea lion for a CT scan was a first. Riding in the back of the zoo van with him, the large animal anesthesia machine and a huge tank of oxygen and manually giving him breaths the whole way was quite an experience.
Edward Quigley, MD, PhD, professor of radiology at U of U Health, led a CT scan of the sea lion’s entire body to diagnose him. “It was logistically pretty amazing,” Quigley said. “Diego was longer than the standard CT scanner table, so we had to be creative to support his hindquarters while imaging.” He adds that the radiology department often lends its expertise and advanced scanning equipment to help Hogle Zoo with complex imaging or critical cases.
The CT scan revealed that Diego had severe degenerative disc disease, a spine condition that involves narrowing of vertebral disc spaces, narrowing of the spinal canal, and bulging discs. These findings explained Diego’s flipper weakness—chronic in his front flippers and progressively worsening in his rear flippers. While serious, this condition is treatable with anti-inflammatory steroid medications.
Road to recovery
Waking up after arriving back at Hogle Zoo, Diego began his recovery journey, closely monitored by the animal care and veterinary teams through the night. In the days following his procedure, Diego’s appetite returned, allowing him to eat enough fish to take his twice-daily steroid medication, similar to aspirin, to treat his back discomfort. He began regaining strength and mobility, even enjoying a brief swim.
Despite advanced spinal disease, Diego continues to participate in his care and is stable. While he does not have full movement of his rear flippers, his mobility has improved. The animal care and veterinary teams assess him daily and adjust training behaviors to minimize movements that could strain his spine. His care team monitors him closely for relapse signs.
Similar to people with chronic degenerative back problems, Diego receives daily medication. His updated routine now includes training for laser therapy, a non-invasive treatment that stimulates blood flow and reduces inflammation.
Additionally, the team is evaluating the pinniped habitat to ensure it supports Diego’s comfort and mobility as his needs evolve.
You can visit Diego and his habitat-mates Maverick, Finn, Mira, and Nika in the Rocky Shores exhibit of Hogle Zoo.
Utah’s Hogle Zoo has amazing teamwork, creativity, problem-solving, stamina, and dedication that allowed us to do something remarkable. Without the University of Utah Radiology Department, a diagnosis for Diego would not have been possible. Diego’s procedure was successful because of teamwork and innovation between animal experts at Hogle Zoo, the best pinniped anesthetist in the world, and a brilliant and willing human radiologist. This monumental effort reflects the zoo’s commitment to advancing animal wellbeing and the importance of partnerships in achieving remarkable outcomes.
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Read Hogle Zoo’s press release here.
