Tula-Tu is first on West Coast to get EEHV vaccine

Medical breakthrough brings new hope for a generation of Asian elephants

Tula-Tu, the young Asian elephant calf at the Oregon Zoo, has become the first elephant on the West Coast to receive a vaccine aimed at protecting against elephant endotheliotropic herpesvirus, or EEHV, a rapidly progressing and often fatal disease to which elephant calves are particularly susceptible.

"This is a huge milestone for us," said Steve Lefave, who oversees the zoo's elephant care program. "Our team has been working with Tula-Tu since right after her birth, building the necessary trust and training for behaviors that allow her to participate in her own health care."

Born Feb. 1, 2025, to Rose-Tu, Tula-Tu now weighs more than 1,300 pounds. This summer, she received two doses of an mRNA vaccine targeting EEHV 1A, the most common strain of the virus. A third dose will be administered in the fall.

In 2018, another of Rose-Tu's calves, Lily, succumbed to EEHV shortly before her sixth birthday.

"Losing Lily to EEHV was devastating for our entire community, and it's something we never want to happen again," Lefave said. "We're so thankful to have a vaccine now to help protect against this virus."

The vaccine was first administered to adult elephants at the Houston Zoo in 2024 and has been rolled out on an experimental basis over the past two years. Tula-Tu is the 18th elephant to receive it.

Researchers have noted no adverse side effects among any of the elephants thus far, and early reports on the vaccine's effectiveness have been positive. Last month, researchers at Baylor College of Medicine and the Houston Zoo shared findings that elephants receiving this vaccination can successfully withstand natural infection without developing severe disease.

"Tula has been doing fantastic," said Dr. Carlos Sanchez, the Oregon Zoo's director of animal health. "She's her usual playful self, and we have seen no negative side effects. Our hope is to provide her the protection she needs until she develops her own antibodies against this disease."

Sanchez, who serves as chair of the North American EEHV Advisory Group Research Committee, says this moment has been years in the making. 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. The current vaccine is the result of 15 years of research led by Baylor College of Medicine and supported by zoos along with other conservation organizations and elephant experts.

"When I started with the advisory group more than a dozen years ago, this vaccine was just a dream," Sanchez said. "It is so gratifying now to see it become a reality."

Collaborating with accredited facilities nationwide, the Oregon Zoo has invested in critical research, testing and monitoring to protect elephants from EEHV.

"Early detection is critical," Sanchez said. "Today, we conduct routine blood monitoring in-house, with veterinary technicians trained to recognize elephant-specific blood cells. We've also partnered with the Oregon Veterinary Diagnostic Laboratory at Oregon State University to run advanced molecular testing. This will allow us to get results right away. We can collect blood samples in the morning and get results by the afternoon. That can be lifesaving."

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 the Association of Zoos and Aquariums' 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.