USUALLY when families drive through the monkey forest at Woburn Safari Park
north of London, the trees ring with the delighted shrieks of children as the
rhesus macaque monkeys clamber over the cars and try to remove the windscreen
wipers. But one day last month, the sound of children gave way to the crack of
silenced rifles.
When the shooting was over, 215 monkeys had fallen from the branches. Next it
was the turn of the 100 rhesus macaques at West Midland Safari Park near
Birmingham, then 89 animals at Blair Drummond Safari Park near Stirling in
Scotland.
The monkeys were killed because they carried a virus that very rarely spreads
to humans, but is deadly when it does. All over Europe, zoos and parks with
macaques are deliberating whether they will have to do the same, or whether less
drastic measures will do. And they are wondering which other animals may be
next.
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Many human diseases have come from animals. Now concerns are emerging that
zoos and animal parks could be a source of animal-to-human infections, or
zoonoses. In the past three years, cows and goats at zoos in Canada and Britain
have spread potentially lethal E. coli O157:H7 to people who鈥檝e stroked
them. Pet reptiles and amphibians cause 93 000 salmonella infections, some
fatal, in the US each year. Seals and other marine mammals in aquaria have given
handlers infections related to TB.
So far monkeys have grabbed the most attention, thanks to the simian herpes B
virus that infects at least 80 per cent of macaques, giving them sporadic cold
sores. In humans, the virus can cause a brain inflammation that kills more than
half the people who get it and leaves survivors with severe neurological
damage.
Human cases are exceedingly rare, however. In the US, which analyses 200
blood samples a month from people bitten or scratched by macaques, there have
been fewer than 40 human cases of herpes B since the virus was discovered in
1933. The main source of exposure is lab work involving the macaques.
With the virus seemingly a remote risk, macaques became popular in safari
parks, where visitors can drive or walk through an area where the animals live
almost naturally. But in 1997 a researcher died of herpes after being splashed
in the eye with liquid from a rhesus cage at the Yerkes Regional Primate
Research Center in Atlanta. This incident was the first to suggest that the
virus can spread in body fluids.
The US did not change its rules for handling macaques. But last year Britain
upgraded herpes B to a 鈥渓evel four鈥� pathogen, the same as Ebola or Lassa fever.
Such pathogens, and the animals that harbour them, are subject to very strict
containment laws. 鈥淚t was to protect laboratory staff,鈥� says Chris Webster,
director of Woburn Safari Park. 鈥淭hey didn鈥檛 think about zoos.鈥�
In February, the park killed 11 monkeys to cut troop numbers, and gave them
routine blood tests. 鈥淎ll were strongly positive for herpes,鈥� says Webster. 鈥淚t
was only then we found out that we either had to put them in containment or kill
them.鈥� West Midland and Blair Drummond then made similar culls, with similar
results鈥攁nd was faced with the same options.
The decision to kill, says Sian Evans of the DuMond Primate Conservancy in
Miami, Florida, 鈥渟eems a bit hasty鈥�. Surely they could have found a more humane
solution. 鈥淲e wish we could have,鈥� says Webster. Unfortunately there were no
level four quarters available. But had there been appropriate containment
facilities, staff would have been at risk when trying to catch and confine the
animals.
鈥淭here would have been much more human exposure if we鈥檇 tried catching them,鈥�
agrees Bob Lawrence at West Midland Safari Park. 鈥淏ut there was no way we could
rule out visitors being exposed in the park if the virus can spread in urine and
saliva.鈥� Safari park visitors open windows and even leave their cars, despite
warnings not to.
The last rhesus macaques in Britain are at Longleat Safari Park near Bath,
where 12 monkeys tested negative. Manager Keith Harris says the monkey forest
will stay open, and Longleat will trap and test the animals regularly.
But that may not be enough. 鈥淭he virus can pop up any time in animals that
test negative,鈥� says Richard Heberling of the Virus Reference Laboratories in
San Antonio, Texas, which tests zoo animals in the US for herpes. It can hide
inside nerve ganglia for years without prompting the immune system to produce
the antibodies detected by all current tests.
A lion-tailed macaque that bit a boy at the Mesker Park Zoo in Evansville,
Indiana, last year was one of six that had tested negative for herpes 17 times
since 1990. After the incident all six tested positive. 鈥淧eople should treat all
macaques as if they are positive for herpes regardless of test results,鈥� says
Heberling.
Frank Rietkerk, curator of the Apenheul Primate Centre near Apeldoorn in the
Netherlands, may have to. At Apenheul, which was the first free-living monkey
park opened in 1971, visitors walk among barbary and lion-tailed macaques. Even
if they test negative, the park might decide to enclose them, just in case. 鈥淚
don鈥檛 know what I鈥檒l do if they are positive,鈥� says Rietkerk. No other country
has laws comparable to Britain鈥檚, which Rietkerk calls an 鈥渙ver-reaction鈥�. 鈥淲e
will try at all costs to avoid a repeat of Woburn.鈥� Rietkerk believes the
emerging Dutch strategy, which is likely to influence European Union policy in
this area, will rely on stricter containment of the monkeys rather than
slaughter.
But if any of his barbary macaques test positive, the impact could be
far-reaching, as the animals are popular in European parks. At three in France,
including one in Alsace where barbaries clamber over a ruined castle, humans and
monkeys come into close contact. And such parks are unlikely to be able to
enclose the monkeys.
No barbary macaque has ever tested positive for herpes, notes David Brown of
the Public Health Laboratory Service in London, which tested the British rhesus
macaques, 鈥渂ut that鈥檚 not to say there aren鈥檛 some鈥�. However, only
rhesus鈥攁nd one cynomolgus macaque鈥攁re known to have infected people.
No human cases have been seen in the barbaries鈥� native range. Gibraltar鈥檚
鈥渁pes鈥�, which occasionally bite tourists, are barbaries.
鈥淭his is all hysteria,鈥� says Evans. 鈥淣o visitor to an animal park has ever
been infected with herpes. People have lived with macaques in Asia for
centuries.鈥� Nor are there any recorded cases caused by the wild rhesus on an
island in Florida鈥檚 Silver River鈥攖hough as only a few laboratories can
diagnose simian herpes B infections in people, rare cases may simply have been
missed. Many of these animals, left over from the filming of Tarzan movies, test
positive for herpes and bite locals. They may be allowed to die off naturally
after a sterilisation programme.
Douglas Richardson, zoological director of the Rome Zoo, feels it will be
necessary to put glass between monkeys and public. But many zoos and safari
parks may decide that the problems of greater containment mean it鈥檚 not worth
saving the animals. 鈥淗ow are they going to clean the droppings and bedding with
that virus in it? You鈥檇 have to handle it like a quarantine kennel,鈥� says
Lawrence at West Midland Safari Park. 鈥淭he costs could be prohibitive.鈥� And it
doesn鈥檛 stop at macaques. Other park primates, such baboons, may harbour as many
as 21 potential human pathogens from monkey pox and leprosy to hepatitis B and
E. coli O157, experts warn.
Much will depend on the European Union鈥檚 forthcoming zoo directive, now being
debated by member states. Its rules for potentially infectious animals will be
set by the decisions now being made in Britain and the Netherlands. 鈥淓veryone鈥檚
watching us,鈥� says Webster. The result could be that macaques in Europe and
America are found safer quarters. Or it could lead to more shots ringing out in
monkey parks around the world.
Wolfram Rietschel, head veterinarian at the Stuttgart Zoo in Germany, says
one keeper there carrying hepatitis A infected a monkey, who then passed it to
four more keepers. Given these risks, he says, 鈥渁ny direct contact of nonhuman
primates and zoo visitors should be avoided鈥�.