Tula-Tu holding steady during treatment for EEHV

Zoo vet says Tula's condition remains guarded but she is 'showing encouraging signs'

Tula-Tu, the beloved Oregon Zoo elephant who became an instant celebrity following her birth in 2025, is holding steady after a week and a half of emergency care for elephant endotheliotropic herpesvirus, or EEHV.

Since her diagnosis last week, zoo care staff have treated the young elephant with antiviral medications, fluids and a series of plasma transfusions to fight the virus.

"Tula remains in guarded condition, but she is showing encouraging signs," said Dr. Carlos Sanchez, the zoo's director of animal health. "Her white-cell counts are nearly back to normal and her viral load is trending down. She appears more alert and her appetite has improved - these are all positive indicators. She's a tough little elephant."

The zoo continues to send blood samples for molecular testing at the Oregon Veterinary Diagnostic Laboratory at Oregon State University as well as Baylor College of Medicine and the Smithsonian's National Elephant Herpesvirus Laboratory.

Tula's mom, Rose-Tu, has been a constant reassuring presence, nursing and comforting her young calf, Sanchez said. Tula also ventured outdoors this week in a behind-the-scenes yard and has spent time with her dad, Samson, plus aunties Sung-Surin and Chendra inside Forest Hall. Care staff say she's been playing with her favorite toy, a large blue ball that used to belong to her mom.

Earlier this year, Tula-Tu became the first elephant on the West Coast to receive an mRNA vaccine aimed at protecting against EEHV-1A, the most common strain of the virus. However, Tula's current infection is from a different, related strain: EEHV-1B. Although EEHV-1B is responsible for fewer reported fatal infections, both variants can cause severe disease in young Asian elephants.

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

Sanchez, who serves as chair of the North American EEHV Advisory Group Research Committee, says EEHV is a latent virus present in nearly all Asian elephants, both wild and in human care. Most elephants develop natural immunity over time, but calves become highly susceptible to the disease as their maternal antibodies decline, typically between the ages of 1 and 8.

Once EEHV becomes active, it can be life-threatening within a few days - as was the case with another of Rose-Tu's calves, Lily, who succumbed to the disease in 2018 shortly before her sixth birthday. But advancements in early detection, vaccines and transfusion protocols have improved survival outcomes significantly.

For nearly 25 years, the Oregon Zoo has contributed funding and elephant blood samples as part of a collaborative international effort to find a vaccine or effective treatment. Collaborating with accredited facilities nationwide, the Oregon Zoo has invested in critical research, testing and monitoring to protect elephants from EEHV.

Sanchez said blood samples from Tula-Tu will help several ongoing studies - including one conducted in partnership with OSU and Baylor to help researchers further understand the vaccine response.

He notes that the virus affects wild elephants as well. Although it is harder to identify and diagnose - and its occurrence in range countries is overshadowed by much more serious threats such as poaching, habitat loss and human-elephant conflict - scientists have confirmed around 200 EEHV deaths in Asian elephant range countries.

"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."

In 2023, Oregon Zoo veterinary staff worked with Malaysian wildlife officials to set up Sabah's first hematology lab to track signs of EEHV in elephants in the wild and in human care. Zoo veterinary staff provide workshops and support on EEHV diagnostics, monitoring, and response, providing clinical training and awareness for wildlife health practitioners across Southeast Asia.

The Oregon Zoo is recognized worldwide for its elephant care program, which has spanned more than 60 years. It has established a $1 million endowment fund supporting Asian elephants, including AZA's SAFE program to advance conservation across all 13 of the species' range countries.

Beyond direct elephant care, the zoo collaborates with local partners in Borneo to create lasting conservation solutions, from replanting forests and establishing protected corridors to fostering peaceful coexistence between elephants and communities.