A Deadly Virus Was Killing Elephants, So Texas Scientists Created a Vaccine

WHO:  Paul Ling, a professor at Baylor College of Medicine, along with the veterinary and elephant care teams at the Houston Zoo.



WHAT: A new vaccine for elephant endotheliotropic herpes virus (EEHV), a devastating viral disease that can swiftly kill young elephants, often just one to five days after symptoms start showing.

WHY IT’S SO GREAT: It’s been fifteen years since Baylor professor Paul Ling, a virologist who specializes in the human herpes virus, got involved in the project to treat and prevent EEHV. It all started with Mac, a two-year-old Asian elephant who died from the condition at the Houston Zoo in 2008. The disease, which can result in severe hemorrhaging and is fatal as often as 80 percent of the time, is the leading cause of death for Asian elephants in North American zoos. It’s also killed wild elephants in at least eight countries.

“It was really a time of turmoil for the zoo, thinking, gosh, should we have elephants? Should we not have elephants?” said Christine Molter, the Houston Zoo’s director of animal health. Mac “was unfortunately not the first elephant to die from EEHV at the Houston Zoo.”

A series of calls after Mac’s death led to Ling’s involvement, which in turn led to new tests for early diagnosis, treatment plans, and eventually the mRNA vaccine. The vaccine was administered for the first time to Tess, a forty-year-old elephant, on Tuesday. (Disclosure: The family of Texas Monthly’s chairman is among the donors who funded research on the vaccine.)

Like the creation of the vaccine, Tuesday’s celebratory moment was a team effort: Jessica Watts, of Ling’s lab, mixed the four vaccine components into one vial. Jennifer Atkinson, the Houston Zoo’s hospital manager, drew it into the syringe. Molter administered the dose, with Ling looking over her right shoulder and elephant supervisor Kristin Windle holding the massive animal in place and reassuring her. Rob Bernardy, the elephant curator, fed Tess her favorite snack—kale. After the injection, she received one of her favorite treats: half a watermelon. As she crunched away on the fruit, spirits (both human and pachyderm) were high.

“It’s not just a singular vaccine we were giving,” Molter said. “It was sort of like an injection of hope, for individual elephants and also for the species.”

Though the disease primarily afflicts younger elephants, an older one like Tess was the perfect first recipient, since she already had antibodies for the virus. She’s also well trained and will be tolerant in the future as the team does regular blood draws to confirm the vaccine’s efficacy and potentially make tweaks to the formula.

“[In the vaccine are] parts of the elephant herpes virus,” Ling said, “that we think are important for the virus to attach to and get into host cells, which is very similar to how the COVID vaccine is manufactured. What we hope that will do is train the elephant’s immune system to recognize different parts of the virus.” At that point, the goal is for the elephant’s body to stop the virus in its tracks or at least slow it down to prevent severe illness or death. If all goes according to plan, the team will share the vaccine with other zoos with vulnerable elephant populations.

Even before they developed the vaccine, Ling and his team had worked to create a polymerase chain reaction (PCR) test, similar to the types used to detect COVID-19 in humans. The ability to test elephants for EEHV was key, because by the time symptoms start showing, they have often sustained so much damage that they can’t be saved. With early detection, the team was able to start treatment and supportive care before the virus could take hold. One elephant, Joy, got extremely sick, but survived thanks to these treatment advancements and is still thriving at the Houston Zoo. Seeing the potential of the partnership, the zoo decided to name their first new calf after Mac’s death “Baylor.”

“I always joke with them and I say, ‘Yeah, they named him Baylor, not to put any pressure on us or anything!’ ” Ling laughed. But clearly, he and his fellow researchers came through: it’s been fourteen years since Baylor’s birth, and Ling and his colleagues, with the close collaboration of zoo employees, have made a breakthrough that could help save wild populations of Asian elephants and even be adapted for the African elephant population, which reacts slightly differently to EEHV.

“We have a WhatsApp group from a conference we attended in Thailand, and members from all over Asia are just so effusively excited and hopeful for this,” said Molter. “To give them so much hope for the future, even if it’s not tomorrow, is tremendous.”