By David N. Leff
Elephants come in two persuasions: Asian and African. In the normal course of pachydermal events, these two species would never meet. But, of late, they began mingling in the zoos of North America and Europe, with fatal consequences.
Elephus maximus is the scientific name for the Asian elephant, but ¿maximus¿ is an exaggeration. A full-grown specimen tips the scales at five to six tons, and measures up to 10 feet high at the shoulder. Its African cousin, Loxodonta africana, can reach 13 feet and eight tons. It¿s famous for its humongous ears and long, flaring tusks.
But those visible differences aren¿t the only ones, as doctor of veterinary medicine Laura Richman (then at the National Zoo, in Washington, D.C.), learned to her dismay. A press conference Thursday, Feb. 18, at the zoo¿s Elephant House paddock told the story to the media:
Nine juvenile, zoo-born elephants in North America ¿ seven Asian, two African ¿ died suddenly and mysteriously between 1983 and 1996. Evidence from electron microscopy, polymerase chain reaction (PCR) and DNA sequencing enabled Richman and her colleagues to identify the two killer culprits as hitherto unknown strains of herpesvirus, one specific to the Asian species, the other to the African.
At home in their native India and sub-Saharan Africa, respectively, each elephant species cohabits in total tolerance with its latent viral passenger. The African model develops benign skin papillomas reminiscent of genital warts in humans caused by herpes simplex virus, a remote viral cousin of the pachydermal pathogens.
As Richman pointed out, ¿It¿s only when the virus crosses species ¿ from African into Asian elephants, or vice versa ¿ that it becomes deadly. Because African and Asian elephants never have contact in the wild, the deadly effects of the virus were not seen until the two species began to mingle, as in zoos.¿
Skin and blood samples from wild elephants in South Africa and Zimbabwe yielded viral DNA almost identical to that found in the dead Asian animals. ¿This is strong evidence,¿ Richman pointed out, ¿that the virus jumps from African to Asian elephants. The evidence that it jumps in the opposite direction is not as strong.¿
In their hunt for the responsible infective agent, the pathologists¿ index case was a 16-month-old, 1,000-pound, female Asian calf, Kumari by name, who died abruptly in the spring of 1995, after a five-day illness. She was the first elephant ever born at the National Zoo.
Antiviral Drug To The Rescue
Three subsequent cases of the highly fatal hemorrhagic disease were soon diagnosed with the cross-species viral infection: one in California in 1996; another in Missouri in 1997; and a third in Florida last year. Once the pathologists had confirmed a viral etiology, keepers at the Springfield Zoo in Missouri dosed their infected female calf with a potent antiviral drug, famiciclin, which is used to treat human herpes. Their young pachydermal patient made a full recovery. A similar happy ending attended the 1998 elephant, treated with the same drug at the Ringling Brothers Conservation Facility in Florida.
¿We were able to cure these elephants,¿ Richman said, ¿which is promising. If caught early, the infection appears to be treatable.¿
Richman (now at the Johns Hopkins School of Medicine, in Baltimore) is first author of a research paper in today¿s Science, dated Feb. 19. 1999. Its title is ¿Novel endotheliotropic herpesvirus fatal for Asian and African elephants.¿
The discovery she and her co-authors report, that both viral versions zero in on the endothelial cells lining their victims¿ blood vessels, explains the zoo-borne infection¿s symptoms and lethal outcome. When they autopsied Kumari, the index elephant, they found millions of copies of the herpesvirus-resembling virion inside the nuclei of myocardial endothelial-cell capillaries, rendering them leaky. Extravasated blood set off internal hemorrhages, which overwhelmed the heart in less than a week.
A similar case, in a young Asian elephant at a circus in Switzerland, was reported in 1997. The year before, an 11-month-old African elephant died at the Oakland, Calif., zoo, with symptoms like those of the index case.
Elephus maximus is a threatened species in India, which means that no more Asian elephants can be exported to the hungry zoos of the western world. The animals are important beasts of burden in the lumber and mining industries of Southeast Asia. They are bred in captivity more frequently than their African counterparts, and their population in the wild is dwindling.
African elephants are threatened by ivory-hunting poachers, and the shrinking of their habitats.
Hence, in the 1980s, western zoos launched in-house programs to breed elephants as a means of preventing their eventual extinction.
This species-survival agenda is now at risk of a herpesvirus epizootic, owing to the commingling of both species.
Virus Holds Species Survival Agenda Hostage
¿Between 1983 and 1996,¿ the Science paper noted, ¿34 Asian elephants were born in North America. Seven of these animals have died with lesions attributed to the endotheliotropic herpesvirus disease, and one recovered after pharmacological intervention. African elephant births in North America have been few, with only seven births in the same time period, and two deaths due to the disease.¿
Johns Hopkins¿ Gary Hayward, senior author of the Science article, found these figures ¿very troubling because they are an endangered species. And also because there may still be carrier African elephants in zoos.¿ The obvious solution, physical separation, won¿t be easy, Richman observed, because some zoos don¿t have the space or facilities. n