Oregon Zoo makes history with experimental vaccine for calf Tula-Tu

(Update: correction, Tula-tu was born in 2025 - article previously stated 2024)

PORLTAND, Ore. (KTVZ) -- Tula-Tu, a young Asian elephant calf at the Oregon Zoo, has become the first elephant on the West Coast to receive an experimental vaccine aimed at protecting against elephant endotheliotropic herpesvirus, or EEHV.

Born Feb. 1, 2025, to mother Rose-Tu, the calf weighs more than 1,300 pounds and received two doses of the mRNA vaccine targeting the EEHV 1A strain.

EEHV is a rapidly progressing disease to which young elephant calves are particularly susceptible, frequently resulting in death. The vaccine is the result of 15 years of research led by Baylor College of Medicine with support from accredited zoos and conservation organizations.

The development follows a history of loss from the virus at the facility. In 2018, another calf born to Rose-Tu, named Lily, died from EEHV shortly before her sixth birthday. Steve Lefave, who oversees the zoo's elephant care program, highlighted the importance of early training and care in administering the vaccine.

“This is a huge milestone for us,” Lefave said. “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.” Lefave noted that losing Lily was devastating for the community. “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 experimental vaccine was first administered to adult elephants at the Houston Zoo in 2024 and Tula-Tu is the 18th elephant to receive it. Dr. Carlos Sanchez serves as director of animal health at the Oregon Zoo and chair of the North American EEHV Advisory Group Research Committee.

“Tula has been doing fantastic,” Sanchez said. “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.” Early clinical reports indicate that vaccinated elephants can withstand natural infection without developing severe disease. “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.”

In addition to the vaccination program, the zoo utilizes diagnostic testing to monitor for infection through a partnership with the Oregon Veterinary Diagnostic Laboratory at Oregon State University. In-house veterinary technicians conduct routine blood monitoring to identify elephant-specific blood cells.

“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.”

Researchers have confirmed approximately 200 EEHV deaths among wild Asian elephants in range countries, where the species also faces threats from poaching, habitat loss and human-elephant conflict. To aid global tracking efforts, Oregon Zoo veterinary staff assisted Malaysian wildlife officials in 2023 to establish Sabah's first hematology lab. Sanchez explained that data collected from captive elephants directly assists wild populations.

“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.”

Tula-Tu is scheduled to receive a third dose of the vaccine in the fall.