- DeLAND, Fla. - - Jonathan
Day suspends a live chicken below a tree as bait to try to catch the creature
that has killed more humans than any other animal. He gloats: "They
don't stand a chance."
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- They are mosquitoes.
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- Despite his bravado, Day, a top mosquito scientist, knows
that in man's long war against them, the little bloodsuckers usually prevail.
Mosquitoes kill more humans worldwide in five minutes than sharks do in
a year.
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- Insect-borne diseases have ravaged America and the world
time and again for centuries. In decades past, America all but vanquished
mosquito-borne malaria, dengue and yellow fever from its territory - but
mosquitoes always come back with another disease. Four different encephalitis
viruses have struck thousands of Americans in the past 20 years. Now comes
a deadly U.S. epidemic of West Nile virus.
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- West Nile virus was an African disease until 1999, but
since then it has spread across much of America, infecting 156 people and
killing nine this summer alone. It won't peak until the first week of September.
Officials at the Centers for Disease Control and Prevention estimated Thursday
that the epidemic could count about 1,000 cases and 100 deaths by the end
of this year.
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- As alarming and dangerous as West Nile is, scientists
like Day say that the ultimate threat to public health is not the disease
of the moment - it is instead the delivery system, the eternal, unconquerable
mosquito. Like the cockroach, they say the mosquito probably would survive
nuclear war.
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- After a few optimistic years when governments talked
of "mosquito eradication," experts now readily admit that mosquitoes
are so pervasive and so hardy - they develop resistance to everything man
throws at them - that scientists now hope simply to not be overwhelmed.
History argues that mosquitoes may be tamped down temporarily, their threat
contained for a time, but the bugs always come back.
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- Deadly mosquito-borne epidemics have swept across America
many times before. The most recent previous one was in 1975, when St. Louis
Encephalitis killed 95 and infected more than 3,000 people.
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- Those numbers pale next to the millions of Americans
who were stricken in the 19th Century with malaria, an often-deadly disease
caused when mosquitoes inject a parasite into a person's bloodstream. Malaria
may be banished in America, at least for now, but it still stalks the Earth,
spread by mosquitoes.
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- "It's an extremely deadly thing. We're losing 2.7
million people each year, mainly in Africa, as a function of malaria,"
said Harvard School of Public Health medical entomologist Andrew Spielman.
"The war is not winnable. We are simply managing our environment."
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- Day and other specialists worry that even deadlier Japanese
encephalitis, Rift Valley fever and Ross River fever may follow West Nile's
path through the United States.
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- "The one lesson of West Nile is that any virus from
any part of the world can get going in a part of the world where it was
previously never known," said Day. "And once it gets going there's
no stopping it. California is still fertile ground. Texas is still really
fertile ground.
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- No matter where you go in this country, there's a (common)
mosquito."
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- While this year's West Nile epidemic is centered for
now in Louisiana, the past triumphs and future hopes of America's annual
mosquito battle are grounded in buggy Florida. What follows is a report
from the front lines, where scientists waging the battle have modest hopes
and much frustration.
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- Day is a professor at the University of Florida Medical
Entomology Lab in Vero Beach, where he predicts future locales of mosquito-borne
disease outbreaks, tests the effectiveness of bug repellents and tries
to calculate precisely the rate of infections in mosquito populations.
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- Day, a 50-year-old former marathoner, is well-suited
to his work. One of his earliest childhood memories is standing in his
back yard while a plane 250 feet overhead sprayed DDT during a 1956 encephalitis
outbreak in his native Massachusetts.
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- Like other mosquito experts, he doesn't itch when mosquitoes
bite. People who get bitten a lot develop immunity to the mosquito chemicals,
although not to any virus the bugs may carry.
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- Pressed by growing concern about the rapid spread of
West Nile disease, Day and his 9-year-old son, Spencer, interrupted a beach
vacation this month to conduct a first-of-its-kind experiment at Hontoon
Island State Park, about 45 minutes west of Daytona Beach. Day was trying
to find out how many mosquitoes in his area are infected with West Nile.
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- Day placed a live chicken in a stocking-like bag that
forced its feathers down, giving mosquitoes a clearer path to bite the
bird. He put the bagged bird into a 5-gallon can equipped with mosquito-trapping
funnels. He repeated the process with a second trap. The birds spent prime
mosquito-biting sunset and sunrise hours as bait.
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- The next morning, Day and his son picked up the traps,
and kept and counted the mosquitoes in them. Over the next several days,
Day tested a week's worth of chickens and 10,000 mosquitoes for West Nile
virus. With more than half of the tests finished so far, there's good news:
No West Nile.
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- If just one in 1,000 mosquitoes has West Nile, the virus
is likely to spread from birds to humans in that area. Day will have final
results around Aug. 26.
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- Epidemics of mosquito-borne disease often start right
after a drought because the dry spell tends to concentrate animals together,
permitting disease to spread quickly from bird-to-mosquito-to-bird. But
mosquito-borne epidemics then usually peter out in one year, as immunity
to the virus builds up in both human and bird populations. They then spread
to new places where immunity has not yet developed.
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- "I think every year we're going to see West Nile
transmission for awhile," Day said. "In terms of human epidemic,
Chicago is high risk; Texas is high risk for next year, for years to come.
Southern Louisiana, at least they should be done."
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- Using his own arms - and his son Spencer's arms, too
- Day has tested consumer mosquito repellents containing the chemical DEET
to determine how long the sprays protect people. The more DEET a repellent
contains, the longer its protection will last. For people spending two-and-a-half
hours outside, 7 percent DEET will do fine, he said. Many bug repellents,
especially those marketed as child-friendly, contain about 7 percent DEET.
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- While Day studies mosquitoes, John Plate just tries to
kill them.
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- A mosquito technician for Indian River County Mosquito
Control, Plate sprays insecticide from his truck at dusk. As he putters
by the trailer homes and swamps of Vero Beach, Plate says this fight is
personal: In Vietnam, Plate was bitten by more than 2,000 mosquitoes one
night and his skin blew up in enormous welts.
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- "It's nice when you've killed a whole bunch of mosquitoes,"
Plate says as he spreads a fine mist of the insecticide permethrin and
lights up the dusk with a flashing yellow beacon. "I'm happy if we
can keep even with them."
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- Often in the past, the mosquito was the clear winner.
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- In 1793, yellow fever ravaged Philadelphia, killing 5,500
out of its 55,000 residents. Yellow fever killed 20,000 people in New Orleans
and Mississippi in 1853, and another 20,000 there in 1878, when the epidemic
ran as far north as Memphis.
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- During the Civil War, 1.3 million Union soldiers contracted
malaria from mosquitoes, and 10,000 of them died - five times as many as
were killed at the battle of Antietam, the war's bloodiest battle. (Malaria
deaths have not been calculated for Confederate soldiers.)
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- In the 20th century, America vanquished malaria and yellow
fever with a combination of quarantine, medicine, hygiene, and chemical
pesticides. DDT made the biggest difference. But the mosquito always returns,
often carrying new diseases.
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- For a short time, experts hoped they had found the answer.
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- Sixty years ago at a government lab in Orlando, U.S.
scientists figured out a way to turn a Swiss-invented moth-killing chemical
into the biggest weapon man has ever fielded in the mosquito war: DDT.
The legendary pesticide won its inventor a Nobel Prize and saved millions
of lives. It was not without flaws, however.
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- In the summer of 1943, E. John Beidler was a young high
school student who helped out around the Army's Orlando-based lab where
DDT was being developed.
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- Beidler and others were standing beside the mosquito-infested
Banana River during the first aerial spray tests of the pesticide. It was
so buggy that their tan mesh belts initially seemed to be "black fuzzy
belts" of swarming mosquitoes.
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- But within an hour, thanks to the DDT spray, there were
"no mosquitoes at all. It was like magic," Beidler said. "All
the government agency people thought that this was the answer for insects."
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- Yet within a decade, experts found that DDT had lost
its effectiveness because mosquitoes developed resistance to it. DDT also
proved poisonous to all sorts of animals and persisted in the environment,
nearly wiping out the bald eagle.
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- DDT was banned in the U.S. in 1972, but is kept as a
malaria-fighter of last resort in Africa and Asia.
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- Beidler has been mosquito control director in Indian
River County since 1955. He knows that victories against mosquitoes are
short-lived.
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- For example, by using an innovative flooding technique
to rob salt marsh mosquitoes of their breeding grounds, Beidler was able
to reduce the number of the pests found in beach traps from an average
of 171 bugs in 1957 to about 2 in 1969.
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- But a few years later in citrus groves in the county's
west end, another kind of mosquito took over - big time. After running
tests, officials calculated that 23 tons of adult mosquitoes infested one
560-acre citrus grove. That's about 8 billion mosquitoes.
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- "If you control 90 percent of the mosquitoes, 10
percent of 8 billion mosquitoes is still a lot of mosquitoes," Day
said.
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- Nevertheless, the fight to contain the mosquito goes
on.
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- To control mosquitoes, experts first try to kill them
as worm-like larvae resting in ponds, often using a bacteria that erodes
the bug's gut. Larvae are easier to kill than flying adults.
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- Few pesticides are aimed solely at the adult mosquito.
There's not a big market for them because governments aren't spending a
lot of money to kill the bugs, said David Brown, president of the American
Mosquito Control Association. Overall, AMCA estimates that local governments
spend about half a billion dollars a year to fight mosquitoes - slightly
less than U.S. consumers spend on fresh doughnuts each year.
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- "We're down to a few tools," Beidler said.
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- Some of the best weapons against mosquitoes are environmental
and lifestyle changes. The draining of wetlands in the 1950s and 1960s
reduced mosquito populations, but as environmental awareness led to expansion
of wetlands, the bugs came back.
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- If you can't eliminate them, at least you can stay away
from them, sometimes. The advent of air conditioners, screen doors, and
television have helped keep mosquito-borne diseases in check by keeping
Americans indoors during prime mosquito-bite hours around dusk and dawn.
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- Mosquitoes find ways to fight back. The nasty striped
Asian Tiger mosquito provides a perfect example.
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- It came to the United States about 30 years ago in a
shipment of used tires and now thrives all over in small puddles of water,
such as those found in tires, cans, and gutters. The Asian Tiger is indiscriminate
in what it bites, which makes it a good "bridge" mosquito to
take diseases from birds to humans.
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- Asian Tigers are also aggressive in mating. A swarm of
mosquitoes mating is a sight to behold, with males massing around the likely
bite victim of a female mosquito, waiting for her arrival.
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- "They just go to the host and hang out and wait
for the females to show up," Day said with a chuckle. "It's like
a bar."
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- Once the mosquitoes pair up, watch out. They're prolific.
Day keeps photographs of a marsh the size of a football field crowded with
wall-to-wall mosquito eggs.
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- That's why Beidler concedes that his job "is to
try to keep it down to a dull roar."
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- ---
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- For more information, check out the following Web sites:
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- The Centers for Disease Control and Prevention's Web
page for mosquito-borne viruses:
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- <http://www.cdc.gov/ncidod/dvbid/arbor/>http://www.cdc.gov/ncidod/dvbid/arbor/
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- Harvard University's mosquito-borne disease page:
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- <http://www.hsph.harvard.edu/mosquito/>http://www.hsph.harvard.edu/mosquito/
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- Florida Medical Entomology Laboratory's Encephalitis
Information System, which has updates on the current situation and predictions
for mosquito-borne disease:
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- <http://eis.ifas.ufl.edu/eis1.htm>http://eis.ifas.ufl.edu/eis1.htm
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- The American Mosquito Control Association's mosquito
information page:
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- <http://www.mosquito.org/mosquito.html>http://www.mosquito.org/mosquito.html
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- ---
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- © 2002 Knight Ridder/Tribune Information Services
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