A young Asian elephant at the Saint Louis Zoo has received a groundbreaking vaccine designed to protect him from one of the deadliest diseases affecting young elephants.
Jet, who is 1½ years old, is the first elephant at the Missouri zoo to receive an mRNA vaccine for elephant endotheliotropic herpesvirus, better known as EEHV.
The virus can damage the lining of an elephant’s blood vessels and may lead to EEHV hemorrhagic disease, a life-threatening condition that is considered a leading cause of death among young elephants in North America.
According to the zoo, mortality rates for young calves that develop the disease can reach between 60% and 80%.
Jet received his first dose of the multi-stage vaccine on May 27 and his third dose on Sept. 30.
Jet, the Asian elephant calf.
“This vaccination is a critical step forward in the decades-long effort to protect Asian elephants from EEHV,” said Dr. Kari Musgrave, the zoo’s director of animal health.
“After years of collaboration with researchers, veterinarians and elephant care experts, we’re thrilled to have Jet vaccinated against this devastating disease.”
The milestone is especially meaningful for the zoo because of its previous experience with EEHV.
Eight years ago, another Asian elephant named Kenzi died from the disease.
“Our team understands just how devastating EEHV can be,” said zoo curator Katie Pilgram-Kloppe. “I can’t describe how it feels to know that Jet has an extra layer of protection against the virus that has threatened his species for decades.”
Jet at the Saint Louis Zoo.
Jet was born with maternal antibodies that helped protect him from disease early in life, but those defenses naturally weaken as he grows.
The vaccine is intended to provide added protection during that vulnerable period, until his own immune system develops a stronger response.
Veterinarians will continue monitoring Jet and measuring his antibody levels through blood tests.
The vaccine itself is the result of years of research.
Scientists at Baylor College of Medicine in Houston and veterinarians at the Houston Zoo began developing a vaccine for EEHV in 2009.
Adult elephants at the Houston Zoo received some of the first doses in 2024, and the vaccine has since been introduced at other zoos across North America. Early results have given researchers reason for optimism.
Jet was born in November 2024 and became the first Asian elephant calf at the Saint Louis Zoo conceived through artificial insemination.
Since then, zoo staff say he has remained healthy, active and curious.
“Jet is a curious young elephant,” Pilgram-Kloppe said. “He loves to run around, play in the dirt, and climb over logs.”
For the zoo’s veterinary team, his vaccination represents more than just an important milestone for one calf. It also offers hope that future generations of elephants may have a better chance of surviving a disease that has taken many young animals in the past.