WASHINGTON -- A mysterious and fatal herpes virus is killing elephants at American zoos and could endanger all zoo elephants, researchers said on Thursday.
Two slightly different versions of the virus -- a distant relative of chickenpox and cold sores in humans -- probably passed from African elephants to Asian elephants and vice versa. The virus kills young elephants, the researchers reported in the journal Science.
"This is very troubling because they are an endangered species," said Gary Hayward, a virus expert at Johns Hopkins University in Baltimore who worked on the study.
If the infection is found quickly, it can be treated with antiviral drugs such as famciclovir, the researchers said.
Zoos are working hard to preserve their elephant populations. Asian elephants, a separate species from African elephants, are especially rare. Zoos can no longer get new specimens from the wild and are forced to breed them -- itself a difficult and lengthy task.
But of the 34 elephants born in United States and Canadian zoos between 1983 and 1996, nine have died from the virus, the researchers reported.
Unlike common herpes-simplex viruses, which attack the skin and lie latent in nerve cells, the new elephant virus attacks endothelial cells -- the cells that line blood vessels, the heart, and other organs. Some of the baby elephants died of heart attacks caused when their blood vessels collapsed.
The first elephant born at the National Zoo in Washington DC was the first known victim of the virus. Her sudden death at the age of 16 months in 1995 baffled zookeepers. Researchers at Johns Hopkins and the zoo started investigating and found evidence of the virus. Though it was hard to tease out, genetic tests eventually confirmed the elephant had been infected with herpes.
Hayward said it was difficult to believe at first, as this herpes virus was so different from any others he had ever studied. "I said herpes viruses don't kill by hemorrhaging, and they don't kill in five days," he told a news conference. "It's actually a very different type of virus, but not related to any other kind of herpes virus that we know about."
Tissue samples from other animals that had died in the US and Canada were also infected. Similar infections were found in elephants in Switzerland and Germany.
When an elephant was born at a circus in Missouri with symptoms of infection, vets gave him famciclovir, usually used to treat genital herpes and shingles in people. The calf recovered, as did another one in Florida.
"It worked like a charm," Richard Montali of the National Zoo told a news conference. "So there are now two young elephants who have recovered and who are doing well today."
The researchers traveled to South Africa and Zimbabwe and found several wild elephants with the blisters associated with herpes, but they were all apparently healthy.
The researchers believe the African virus exists harmlessly in African elephants -- somewhat akin to cold sores -- but when passed to Asian elephants it can kill. They have no evidence of a similar natural virus in Asian elephants, but believe there must be one, and that it would kill African elephants. Hayward said it makes sense that a virus would be deadly in one species of elephant, but not the other.
"Asian and African elephants are separated by 3 million years of evolution and their viruses are separated as well," he said.
Now the team is checking to see how the virus is transmitted and to see if perhaps separating Asian and African elephants in zoos and circuses will help prevent infection.
"It's a big thing to do," Montali said. "Once they are socialized it is hard to desocialize them."
Copyright© 1999 Reuters Limited.
