The San Diego Zoo's macaque monkey carries herpes B virus

"Not an appropriate species to have at the zoo."

The macaque monkey lets a golden stream tinkle from his perch on the upended tree trunk. Maybe he's nervous. He's five feet behind the fence here in the Sun Bear Forest area of the San Diego Zoo. A group of kids lean over the railing, five feet on this side of the fence.

Ten feet, and a wire fence with large-mesh (two-inch by three-inch) wiring is all that separates these curious young humans from one of their closest cousins, India's lion-tailed macaque monkey. If the macaque chose to leap onto the wire mesh, with the kids craning their necks in towards him, the distance between man and monkey could close to a mere four feet. Easy spitting distance.

Or urine-spraying distance.

Last month, a 22-year-old primate researcher in Atlanta died when a macaque monkey she was studying squirted some fluid -- probably urine -- into her eye. She succumbed soon after to simian herpes. The herpes B virus.

Herpes B is the macaque equivalent of humans' herpes simplex. It is usually transmitted sexually among the monkeys and results in oral lesions. It is nothing more than a minor nuisance to them. But when a human contracts it, she or he can come down with potentially fatal meningoencephalitis. Seventy percent die.

So nobody in the research community was surprised at the young researcher's death. Yet everyone was shocked at how she caught the virus. Until that incident, it was believed you could only contract simian herpes if a macaque monkey bit or scratched you and drew blood. That the lab worker could become infected from a splash in the eye sent a shiver through the veterinary and zoo world.

It also raised a question relevant to San Diegans: how safe is it to leave macaque monkeys on display within a few feet of an unsuspecting public? Should the San Diego Zoo risk inviting visitors to stand within spray-range of a species known to harbor this lethal virus?

At Vilas Zoo in Madison, Wisconsin, which houses one of the largest macaque colonies in the world, zoo director Dave Hall has decided the risk is too great.

"My personal opinion is that [the macaque monkey] is probably not an appropriate species to have at the zoo, given the developments about the herpes B virus," he recently told the Wisconsin State Journal. "It does definitely make a significant impact."

Hall will soon be sending away all 150 of his stump-tailed macaques and rhesus monkeys, also of the macaque genus.

Not so San Diego Zoo. "I don't take these human tragedies lightly by any means," says Donald Lindburg, director of the zoo's behavioral division. "But every time we have an incident [such as the Atlanta death], we have people coming out with ever-more draconian measures to respond to this kind of thing. If an elephant kills a keeper -- and elephants kill more than two keepers every year [in zoos worldwide] -- we don't say, 'Let's kill all the elephants.' So we do not overreact to these kinds of situations either, and say, 'Let's kill all the macaques,' It's a manageable risk."

Lindburg, a nationally recognized expert on macaques, acknowledges that scientists don't yet know everything about ways herpes B could be transmitted. But he says that most people appear to have a resistance to it. The proof, he says, is in the figures.

"When we consider that hundreds of laboratory macaques around the world are intubated, injected, bled, or otherwise handled each day," he wrote in a 1993 editorial in Zoo Biology, a journal he edits, "the rate of exposure during 60-plus years of biomedical research must approach an astronomical figure."

Yet, he writes, most reliable figures reveal an average of one case of a laboratory worker being infected every 2.5 years over the past 60 years. And laboratory workers' contact with the monkeys is far more frequent -- and intimate -- than zoo workers'.

"Zoo personnel are rarely exposed to their animals in the ways that are considered necessary to spread the virus to humans [bites, punctures]. If I am anywhere near the mark, zoo personnel have experienced over 11 million exposures to macaques since the first human case of herpes B infection was reported in 1932. How many cases of herpes B in zoo personnel have been reported? To my knowledge, none."

To make sure that doesn't change, Lindburg says, San Diego Zoo takes extraordinary precautions with its zoo workers.

"Here in the zoo, we don't touch the animals unless they go to the hospital for some procedure, and then everybody's wearing gloves and masks. We have a different level of contact in a zoological garden than you would have in a research facility, where they do a lot of invasive kinds of techniques. They are handling the animals. They get direct exposure."

Lindburg says zoo staff also wear protective masks, gloves, and plastic lab coats when they, for example, hose out the monkeys' compound and risk being splashed by water laced with urine or feces.

Lastly, San Diego's macaques are regularly tested for the virus (it does not attack any other species of monkey). When checked three weeks ago, they all tested negative. Despite this, Lindburg acknowledges nearly 100 percent of macaques do carry the virus. It stays hidden in dormant mode until they become stressed or weakened by illness. He sees the need for "national protocols" on safety to be set by the American Association of Zoo Veterinarians and has criticized their lack of action.

Lindburg confesses to one weakness: he loves these animals. He first studied them as a graduate student in their native India. And as their forest environment shrinks, their existence on earth is in question. His major crusade is not so much to display macaques but to participate in a captive-breeding program to help keep their numbers up.

"Perhaps," he writes, "if the threat from infective macaques were visually perceived, like those from speeding autos and muggers, we would have come to terms with it by now. But in fact we are dealing with an organism so small that 100 million of them packed together could easily fit on the period at the end of this sentence."

Still, he says the zoo has no intention of copying the "paranoia" of some zoos and getting rid of its six or seven macaques at the zoo, or the troop of 16 (not on display) at the Wild Animal Park. "We have training, we have regular inspections. We feel like we're already doing everything humanly possible to protect our staff."

But what about the public? What about those macaques urinating just five to ten feet away from us, with no glass to protect us from urine spray?

"You cannot make the public dress up [in protective gear] as they come into a zoo to see these animals on exhibit. We do not knowingly put anything out there that would be a threat to the public."

He says the chances of herpes B being transmitted through the wire mesh is almost nonexistent, although he recognizes some risk always exists.

"How could you possibly be 100 percent safe unless you just totally closed those sections of the zoos or got rid of those kinds of primates? You don't go out and cut down all the trees on the ski slope because a couple of people crashed into them."

"I think that I would tend to be a little more conservative than [Lindburg] is on this issue," says Dr. Joe Kemnitz, the man in charge of the Wisconsin macaque and rhesus monkey colony that is being dispersed, at least partly because of last month's herpes B death. "My own personal position as director of the Wisconsin Primate Center is that I would not ever want one of our animals to infect a visitor of the zoo. In recognition of the fact that contracting the virus is so often fatal, even if it's a very low risk, to my mind it's a recognized risk and an avoidable risk. I think that macaques can be safely displayed in appropriately designed displays. [More Plexiglas between monkeys and public] would be one solution. Another would be simply imposing sufficient distance between the public and the animals."

Lindburg's colleague, Dr. Bruce Rideout, pathologist for the San Diego Zoo, disagrees. "From a medical standpoint," he says, "I don't think there's a big risk. The virus is not known to be transmitted by aerosol, so the kind of situation we have here should not pose a significant risk. I don't think our zoo visitors have anything to be concerned about. If they wanted to be concerned about disease problems, I'd be a lot more worried about the person standing next to me than I would be about the primates in the enclosure."

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