Genetic tests suggest that Chai, transferred from Seattle, was likely the source of a virus that killed a 4-year-old female elephant at the Oklahoma City Zoo.

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New genetic tests suggest that the elephant Chai was likely the source of a herpes virus that killed a 4-year-old female at the Oklahoma City Zoo.

The calf, called Malee, died Oct. 1 — less than five months after Chai and her herd-mate Bamboo were transferred to Oklahoma from Seattle’s Woodland Park Zoo.

Zoo records show that Chai exhibited signs of an active herpes infection between Aug. 7 and Oct. 5. Chai died Jan. 30.

Genetic analyses, obtained through a public-records request, show that the subtype of EEHV-1A — or elephant endotheliotropic herpes virus — Chai was shedding is genetically identical to the subtype that attacked Malee.

“My sense of it is that there is a likelihood that these are epidemiologically linked,” said Philip Pellett, a herpes expert at Wayne State University School of Medicine who has written about elephant forms of the virus. “It’s not unequivocal.”

Much is unknown about elephant herpes viruses and their transmission, said Pellett, former head of the herpes-virus group at the U.S. Centers for Disease Control and Prevention.

While the most plausible scenario is that Malee got sick because she was exposed to high levels of viral particles shed by Chai, it’s also possible that the young elephant already had the virus or was exposed by another elephant.

“I would have trouble convicting on this, but it’s certainly a pretty high index of suspicion,” Pellett said.

Oklahoma City Zoo officials did not respond to requests for comment but told a local television station they agree that Chai passed the virus to Malee.

The zoo also issued a news release about the genetic tests but failed to mention the genetic match.

When Malee died, the zoo said there was no link between her virus and the arrival of the Seattle elephants.

Woodland Park Zoo closed its elephant exhibit in 2015, after the death of another elephant, Watoto, and continuing controversy over the ethics of captivity for such large mammals.

The decision to transfer Chai and Bamboo to Oklahoma City was hotly contested by advocates who wanted the two animals retired to an elephant sanctuary.

Chai died in Oklahoma less than four months after Malee. The necropsy blamed a combination of emaciation and a blood infection from skin abscesses. Records showed the 37-year-old female suffered a series of health problems before her death, including two times when she couldn’t get up on her own.

Oklahoma zoo staff said last week they suspect a tooth infection, not the abscesses, may have been the source of the bacteria that swept through Chai’s body. Herpes was not implicated in her death.

As in humans, most captive elephants carry herpes viruses, usually in a latent and hard-to-detect form. It’s not clear what triggers some animals to develop active outbreaks, during which they can shed large amounts of virus.

Oklahoma zoo officials said previously that all of their elephants carry ­EEHV-1A, so Malee was certainly exposed to versions of the virus before Chai arrived.

Herpes is a major killer of young, captive elephants. The calves seem to be most vulnerable between 1 and 4 years of age, and when they are being weaned, said Dr. Heather Rally, a veterinarian for People for the Ethical Treatment of Animals.

“They’re not being protected by their mother’s antibodies anymore, and that can make them more susceptible when they’re exposed to the virus,” she said.

Records show that Chai was the only herd member actively shedding virus in the months before Malee fell ill. At the height of Chai’s infection, analysis of fluid from her trunk contained up to 30,000 viral particles per test sample, which is a significant level, Pellett said.

“The timing of it certainly is there and is part of it, but the genetic similarity is the thing that says there is a common source for those viruses,” he said.

What’s unclear is whether Chai brought the virus with her or picked it up from one of the Oklahoma elephants.

There was no record of Chai being infected with EEHV-1A during the more than 30 years she lived in Seattle, said Woodland Park spokeswoman Gigi Allianic.

Chai’s calf, Hansa, died from a herpes infection in Seattle in 2007, but the cause was a different strain from the one that killed Malee.

It’s possible Chai had a latent infection that was never detected in Seattle but flared into sickness and viral shedding in Oklahoma due to the stress of the move and her various health problems, Rally said.

“We do have reason to believe that herpes outbreaks and shedding happen at times of stress,” she said.

Another possibility is that a depressed immune system left Chai vulnerable to a new virus in her new environment, Rally said.

Without detailed genetic analysis of herpes viruses carried by other elephants at the Oklahoma City Zoo, it’s impossible to pin down the source of Malee’s fatal infection beyond any doubt, Rally pointed out.

The genetic subtyping was conducted at the National Elephant Herpes Virus Laboratory at the Smithsonian Conservation Biology Institute. Research there aims to better understand the viruses, how they spread and how to protect young elephants.

“This is a difficult problem, … and in may ways it’s still early days,” Pellett said.

Opponents of elephant exhibits say zoos should stop breeding elephants and exposing them to the threat of the virus. A Seattle Times investigation in 2012 found that two captive elephants die for every one that is born, and that 40 percent of young zoo elephants die.

“We warned both Woodland Park Zoo and the Oklahoma City Zoo that Chai and Bamboo could introduce the risk of spreading EEHV,” said Alyne Fortgang, co-founder of the advocacy group Friends of Woodland Park Zoo Elephants. “All breeding should end immediately at this infected zoo.”

The Oklahoma Zoo has one calf, 15-month-old Achara. Records also show that the zoo inseminated a 19-year-old female, Chandra, in November.