WASHINGTON -- Scientists have solved the mystery of what killed at least nine zoo elephants across North American in recent years, a discovery that could help protect captive herds of an animal that is threatened in the wild.
In a triumph of medical detective work, scientists from the Johns Hopkins University School of Medicine and the National Zoo identified the killer as a herpes virus that preys primarily upon young Asian elephants raised in captivity.
The diagnosis has also led to a cure: an anti-viral drug that is ordinarily used to combat herpes infections in humans.
"It's a great feeling," said Dr. Laura Richman, a Hopkins veterinary researcher who began looking for answers four years ago.
"If we're not curbing the deaths of these younger elephants, we're not going to have the elephants around. We'd like to control if not stop it completely."
The virus, a strain that has never before been identified, has killed seven of 34 Asian elephants born in North American zoos since 1983, scientists said.
Two African elephants have also died in recent years from a closely related virus. Scientists suspect that some Asian elephants also have become sick with the virus at zoos in Europe.
"We consider this as quite an important pathogen that needs to be checked," said Richard Montali, senior pathologist at the National Zoo, who also took part in the investigation.
Scientists have turned their attention toward developing a simple blood test that can detect which animals are carriers, capable of passing the infection to others. About 500 elephants are in captivity in North America.
A report of the finding appears in today's issue of the journal Science. The discovery was announced yesterday outside the elephant house at the National Zoo.
The search for answers began in 1995 at the National Zoo when Kumari, a beloved 16-month-old female, suddenly became lethargic and stopped eating.
Her neck and trunk swelled, and her tongue turned purple. Five days into her illness, the 1,000-pound youngster died.
A postmortem exam revealed that she had developed bleeding in her heart, liver and abdominal cavity, apparently from an infectious agent that had invaded the cells lining blood vessels.
DNA analysis revealed the culprit to be a new type of herpes virus -- only distantly related to the ones that cause cold sores, genital lesions, chickenpox and shingles among humans.
Scientists were stumped. Herpes viruses don't ordinarily cause devastating, hemorrhagic illnesses. And the virus must exist elsewhere -- but where?
Richman, who was working at the National Zoo as a veterinary resident, began searching the records of other zoos. Finding 25 elephants that died mysteriously, she asked the zoos for microscope slides and tissue samples.
Among those, she found the herpes virus in seven Asian elephants and two Africans.
Dr. Gary Hayward, a Hopkins virologist who was called into the investigation, said the virus that struck the Asian elephants has long infected African elephants in the wild -- perhaps for millions of years -- causing nothing more than harmless skin lesions.
But when the African and Asian elephants were brought together in zoos, the virus jumped to the Asians and caused a fatal illness.
The pattern made perfect sense, said Hayward. Typically, herpes viruses cause serious illnesses when they strike a body with an impaired immune system -- such as a person with AIDS -- or jump from one species to another.
African and Asian elephants are separate species, having evolved apart for 3 million years. The species can be easily differentiated: Africans are bigger and have larger, floppier ears.
Though closely related, the virus that killed two African zoo elephants is not the same one that jumped to the Asian elephants. Scientists say they don't know whether it exists more widely among either species.
It was a stroke of good luck that the drug, famcyclovir, was ever tried.
A zoo in Springfield, Mo., had lost an elephant to the disease in the early 1990s and was suddenly faced with another ailing pachyderm in November 1997. On a hunch, a local infectious disease expert recommended the drug, which is used to treat humans with herpes sores and shingles.
Since then, the medication has also saved an Asian elephant at the Ringling Brothers conservation park in Sarasota, Fla. The medication comes in pill form and is given three times a day for three or four weeks, either orally or rectally.
The discovery could have a major impact on the ability of zoos to maintain their stocks of Asian elephants. The animals are endangered in the wild, so zoos depend on captive breeding to replace older elephants as they die.
Since 1900, about 100 Asians have been born in captivity -- and at least 11 have become ill with the herpes virus.
At the National Zoo, handlers still get tearful when talking about Kumari, whom they remember as a playful if mischievous animal who loved to frolic in the pools outside the elephant house.
"She was a bundle of joy, eager to learn, eager to experience life," said Marie Galloway, the elephant manager. "Like any youngster, she was into trouble, into manipulating the animals and the people around her.
"It was the hardest death I've dealt with."
Pub Date: 2/19/99