An Asian elephant at Houston zoo in the US has received the first mRNA vaccine against herpes, which is the leading killer of Asian elephants calves in captivity.
Tess, a 40-year-old Asian elephant, was injected with the trial vaccine at the Texas zoo in June, after a spate of deaths in juveniles in zoos around the world from the elephant endotheliotropic herpesvirus (EEHV).
Dr Paul Ling, who researches herpes in humans at Baylor College of Medicine in Houston, developed the elephant mRNA vaccine, which is designed to boost the immunity of young elephants.
“When elephants are born, they have a tremendous amount of antibodies that they get from their mother,” he said. “When the female elephant gives birth, she’s probably already had this virus so she gives protective antibodies to her baby, and they last for a certain period of time. Our vaccine is designed to give these young elephants enough immunity that they’ve lost over time.”
The mRNA vaccine is similar in design to the Covid-19 vaccines used in humans during the recent pandemic, and aims to prevent serious illness and death from EEHV in young Asian elephants.
The virus can cause a lethal hemorrhagic disease in Asian elephants, similar to the effects Ebola has on humans. Researchers believe it is passed among Asian elephants through their trunks. First discovered in 1990 and scientifically described in 1999, the virus is a major driver of Asian elephant deaths in captivity.
This month, two juveniles died from the virus at Dublin zoo. Zoos in Chester, Melbourne and Zurich are among those that have lost several baby Asian elephants to the disease. In symptomatic elephants, it has a mortality rate of about 70%.
While the virus has been recorded in wild populations and fatalities have been recorded, experts are unsure how much impact it is having on wild Asian elephants or whether a vaccination programme would be practical. There are fewer than 50,000 of the species in the wild and they are threatened with extinction. Habitat loss, poaching and genetic isolation are all considered bigger threats to their survival.
A Chester zoo spokesperson said they thought the elephant herpes virus was a threat to the long-term survival of the Asian elephant, adding that reports of fatalities in India, Nepal, Myanmar and Thailand were on the rise.
“The only long-term solution to beating EEHV is to find a safe and effective vaccine, which is most likely to be achieved through zoo-led research,” the spokesperson said.
“While the global conservation community has made significant steps towards finding a viable vaccine, further work and time is needed before we have the answer we’re all so desperately searching for – scientific confirmation that the vaccine is effective in preventing EEHV.”
Researchers are monitoring the health of Tess, and Houston zoo plans to inoculate more Asian elephants later this year if no side effects are recorded. The mRNA was developed in a partnership between Houston zoo, Baylor College of Medicine and the Dallas-based “de-extinction” company Colossal.
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