Three other offspring of Hansa's sire, the late Dickerson Zoo elephant Onyx, exhibited herpes symptoms in the past decade. Two of those elephants died between 2000 and 2002 after showing such symptoms and a third, Chandra, was successfully treated for herpes in 1997, according to Associated Press accounts.
Chai, Hansa's mother, was sent to the Dickerson Zoo, in Springfield, Mo., in September 1998 for breeding. Hansa, born in November 2000, was one of 12 elephants sired by Onyx, who died of a ruptured intestine in 2002 at an estimated age of 38.
When asked whether Woodland Park officials knew about Chandra's herpes treatment before sending Chai to Onyx, Deputy Director Bruce Bohmke said he would have to check zoo records. But he said the issue was irrelevant because Hansa died of a previously unknown version of the virus.
"It would be irresponsible if we knew for a fact that this outcome was going to happen," Bohmke said. "But it wasn't clear then, like it would be now in hindsight. This is also a different kind of herpes."
In Hansa's case, the disease attacked the blood vessels in the 6 1/2-year-old elephant's body, zoo officials said. She died June 8 after showing mildly reduced appetite and activity. She did not exhibit any of the signs that accompany the previously identified herpes viruses, which include a purple tongue or skin lesions.
"We were still pretty sad but grateful to find out the cause," Bohmke said Monday.
Because the virus is new, zoo officials have no way of testing to see if the other three elephants at the Woodland Park Zoo have it. The zoo's other elephants: Chai, 28; Bamboo, a 40-year-old Asian elephant; and Watoto, a 38-year-old African elephant, show no signs of illness, said Dr. Kelly Helmick, Woodland Park's interim director of animal health.
Woodland Park had attempted to breed Chai again. The most recent effort to artificially inseminate her, in March, was unsuccessful, zoo officials said recently.
Previously, scientists had identified two other types of herpes virus known to cause disease and death in wild and captive African and Asian elephants. Hansa was initially tested for both, but because the still-unnamed virus that attacked her was genetically different from the two known viruses it could not be detected, Helmick said.
Younger elephants, up to 10 years old, are more susceptible to such disease, she said.
Herpes is a common type of virus in mammals; the virus is species specific, Bohmke said.
In elephants, the virus can produce "a very rapid disease that occurs very quickly with not a lot of warning," said Dr. Scott P. Terell, a veterinary pathologist and the elephant species survival plan pathologist for the Association of Zoos and Aquariums.
Herpes has been known to kill elephants within 24 hours. There have been 21 known cases of elephant herpes virus involving Asian elephants in North America. Only three have survived, Bohmke said.
There is no vaccine for the two previously identified elephant herpes viruses. Scientists were able to successfully able to treat the three elephants with an anti-viral drug used to treat human herpes.
A telltale grouping of red dots on the nucleus of Hansa's blood cells led Dr. Michael M. Garner, a veterinary pathologist, to suspect herpes even though early tests turned out negative, Terell said.
Dr. Laura Richman, a veterinary pathologist at the Smithsonian National Zoo who specializes in elephant herpes viruses, later confirmed that a new form of herpes was the cause of death and was able to classify the new virus through DNA testing.
Richman, a leading expert in elephant herpes viruses, said that very little was known about the new virus and that it would not be accurate to draw parallels to the previously known diseases.
Scientists know elephant herpes viruses can be passed from elephant to elephant, either through birth or through contact with another infected elephant, Terell said. The herpes virus has never been found in elephant semen samples, Richman said.