 |
Scientists at WSU and elsewhere have put in a lot of good work
tracking pathogens and learning their ways. But even with all the
progress of recent decades, we have just a fragmentary
understanding of what we’re dealing with and where the next
outbreak might come from. It’s a sure bet that other pathogens are
out there, chugging along in their animal hosts and fully able to
move into humans if they get the chance.
“Diseases often emerge in strange ways, often as a result of
human activities that bring species together that don’t normally
come together,” says ecologist Storfer. He describes the
combination of events that led to an outbreak of Nipah (NEE-puh)
disease in Malaysia in 1998-99. Over the course of a few months,
the newly recognized disease afflicted 265 people with fever,
headache, convulsions, and coma. It killed 105 and left many others
with persistent neurological problems.
Storfer says the virus that causes the disease is carried by
fruit bats, which themselves aren’t much affected by it. As forests
were cleared to make room for the expanding human population, the
bats began to forage into orchards and other human establishments,
such as pig farms. The fatal chain of events sounds like a
biological Rube Goldberg machine: a bat grabs a piece of fruit from
the orchard; after taking a few bites, it drops the fruit within
reach of the pigs; a pig eats it, picking up the virus from the
bat’s saliva on the fruit; the virus gives the pig a flu-like
respiratory disease; when the pig coughs or sneezes, its human
handler catches it.
“Humans cannot get it from the bat,” says Storfer. “It has to go
through the pig, mutate inside the pig, and then it’s infectious to
the pig workers. You have to bring bats, pigs, and humans all
together in the same place in order for this thing to go from bats
to humans. Because you could lick the bat saliva and not get
it. It’s got to go through the pig.”
Tom Besser suspects the Nipah virus has spread to humans and
domestic animals before, but not in such large numbers.
Encroachments into forested lands, coupled with skyrocketing
density of people and livestock, have created conditions that could
allow the virus to attain epidemic proportions. The Malaysian
government squashed its budding epidemic by killing nearly a
million domestic pigs in the affected areas. No cases of Nipah
disease have been reported there since, but a few appeared in
Bangladesh and India in 2001. That suggests the Malaysian outbreak
might have been just a warm-up for a main event yet to come. Fruit
bats range throughout south and southeast Asia, and everywhere
they’ve been tested, they are positive for the virus; and human and
pig populations in the region continue to expand.
The issue of diseases passing from wildlife and domestic animals
to people is “one of the most important challenges we’re going to
face, I think, over the next century,” says Storfer. Surveillance
of humans and livestock is spotty; monitoring of wild species is
nearly nonexistent. Nobody is really watching the wildlife from
which new diseases might emerge. Even a disease that causes severe
problems in wild animals can go unnoticed for years. How bad does
an outbreak in wildlife have to be for someone to send up a flare
and say, hey, we’ve got a problem here?
“That’s the $100 million question,” says Storfer. “One of the
concerns is this idea that there’s a surveillance bias, that we’re
only seeing really nasty things, because then you see a big die-off
of something. But we’re not seeing a lot of the pathogens that jump
hosts, that might get worse someday.
“How do you prepare yourself? I don’t really know. You try to
pick the one that’s going to be the worst one, and do something
about it.”
Page
1
2
3
4
5
Washington State Magazine Home
|
|
Land-use changes that bring people and livestock into
contact with wildlife are exposing us to pathogens we may not have
encountered before. And in an age of global trade and travel, one
infected person or animal can carry a disease across
continents.
Wild animals are a source of many pathogens that might infect
us, but the reverse is also true: we and our domestic animals
harbor diseases that can devastate wild populations.
| |
