Tula-Tu fights off EEHV infection as doctors express cautious optimism
Bend, Ore. (KTVZ) --- Veterinary experts at the Oregon Zoo have launched a comprehensive treatment plan for Tula-Tu, an Asian elephant calf battling elephant endotheliotropic herpesvirus, or EEHV. Care staff alerted veterinarians on Oct. 24 after noticing subtle changes in the calf's behavior and energy levels.
Testing at the Oregon Veterinary Diagnostic Laboratory at Oregon State University confirmed an elevated viral load of EEHV the following day. The diagnostic results prompted veterinary staff to initiate plasma transfusions alongside antiviral treatments to help fight the virus.
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.”
Earlier this year, Tula-Tu became the first elephant on the West Coast to receive an mRNA vaccine designed to protect against EEHV-1A, the most common strain of the virus. Her active infection is caused by EEHV-1B, a related strain. Although EEHV-1B accounts for fewer reported fatal cases, both variants can cause severe illness in young Asian elephants. “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. While adult elephants typically develop natural immunity, calves become vulnerable between ages 1 and 8 as maternal antibodies decline. Active infections can become life-threatening within days, as occurred in 2018 when another calf, Lily, died from EEHV shortly before her sixth birthday.
For nearly 25 years, the Oregon Zoo has supported international research into vaccines and treatments for EEHV. Blood samples collected from Tula-Tu will contribute to ongoing joint research with Oregon State University and Baylor College of Medicine to analyze vaccine responses. 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. In 2023, Oregon Zoo veterinary staff partnered with Malaysian wildlife officials to establish Sabah's first hematology lab to track EEHV in wild and captive elephants, providing clinical training for health practitioners across Southeast Asia.
