Oregon Zoo Treats Elephant Calf for EEHV

Oregon Zoo Veterinarians Treat Tula-Tu for Elephant Herpesvirus

As reported by KTVZ, a robust care strategy has been put in place by veterinary professionals at the Oregon Zoo for Tula-Tu, an Asian elephant calf dealing with elephant endotheliotropic herpesvirus, or EEHV. Care staff alerted veterinarians on Oct. 24 after noticing subtle changes in the calf’s behavior and energy levels.

The following day, analysis at the Oregon Veterinary Diagnostic Laboratory situated at Oregon State University verified a high viral load of EEHV. Following these diagnostic findings, the veterinary team started antiviral therapies along with plasma transfusions to combat the illness.

Dr. Carlos Sanchez, director of animal health at the Oregon Zoo, emphasized that rapid intervention is essential when responding to potential infections.

“Early detection is critical,” Sanchez said. “We conduct routine blood monitoring in-house, with veterinary technicians trained to recognize elephant-specific blood cells. Right away, they could see Tula’s white-cell count was low, so we started her on antiviral medications while we waited for advanced molecular testing to confirm or rule out EEHV.”

Sanchez reported that Tula-Tu has remained stable throughout treatment.

“The combination of stable viral loads, normal platelet counts and improving white cell counts suggests a favorable trajectory,” Sanchez said. “She’s not out of the woods yet, but these findings provide grounds for cautious optimism. Diagnostics and treatment for this disease have advanced so much over the past few years. Every hour of stability brings her one step closer to recovery.”

Previous Vaccine Administration and Strain Differences

Tula-Tu was given an mRNA vaccine earlier this year to guard against EEHV-1A, the most frequent strain of the virus, making her the initial elephant on the West Coast to receive it. Her active infection is caused by EEHV-1B, a related strain. Both variants are capable of causing severe disease in young Asian elephants, even though EEHV-1B is linked to a lower number of documented fatalities.

“We do not know whether the EEHV-1A vaccine is protective for the -1B variant,” Sanchez said. “It’s possible, but to what degree remains unknown.”

Sanchez serves as chair of the North American EEHV Advisory Group Research Committee. He explained that EEHV is a latent virus present in nearly all Asian elephants. Calves run the risk of becoming susceptible between the ages of 1 and 8 as maternal antibodies wear off, whereas adult elephants generally build up natural immunity. A swift, multi-day escalation is possible for active infections, mirroring the 2018 case of another calf named Lily, who succumbed to EEHV shortly before turning six years old.

Ongoing International Research and Diagnostics

For nearly 25 years, the Oregon Zoo has supported international research into vaccines and treatments for EEHV. To help evaluate vaccine responses, blood samples gathered from Tula-Tu will support collaborative research efforts alongside Baylor College of Medicine and Oregon State University. Scientists have documented approximately 200 EEHV deaths among wild Asian elephants.

“The work we’re doing now could play a significant role in protecting future elephant calves from the disease, including those in range countries,” Sanchez said. “It’s very difficult to study the virus in wild elephants, but zoos can monitor the elephants in their care closely and obtain samples of blood and other fluids.”

The zoo has also assisted international diagnostic efforts. Establishing Sabah’s first hematology lab to monitor EEHV in both wild and captive elephants was accomplished in 2023 through a collaboration between Oregon Zoo veterinary staff and Malaysian wildlife officials, which also delivered clinical training to health workers across Southeast Asia.

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