The Perils of Pollen and Tricky Ticks

georgia · medicine forum Guru Joined: 06 May 2005 Posts: 505

http://www.nytimes.com/2006/06/19/health/healthspecial/19insects.html?_r=2&oref=slogin&oref=slogin

http://tinyurl.com/s9d87

June 19, 2006

The Perils of Pollen and Tricky Ticks

By DONALD G. McNEIL Jr.

THERE is a "War of the Worlds" quality to the outbreak of a new
disease:
something foreign appears on these shores and, ignored or misdiagnosed
at
first, spreads quickly, killing a few earthlings - until someone
notices.
Then, suddenly, panic spreads faster than the threat, and a terrified
populace demands that the government do something - even if, looked at
realistically, the disease is less of a threat than the flu.

That's the story behind two warm-weather plagues, West Nile virus and
Lyme
disease. But there are differences. West Nile entered the country only
seven
years ago, while the Lyme scare began in 1975. Nonetheless, West Nile
has
hurtled across the continental United States, while Lyme is still
spreading
slowly from the areas where it was first diagnosed: New England and
Wisconsin.

Another disease that is, for some people, worse in warm weather -
asthma -
also breaks out around the nation during spring and summer, but in
unpredictable patterns.

So which of these diseases poses the greatest threat?

Asthma, by far. The Centers for Disease Control and Prevention
estimates
that asthma kills about 4,000 to 5,000 people a year - 20 times as many
people as West Nile does.

Lyme disease, which can usually be cured with antibiotics, is almost
never
fatal, though there are rare cases in which victims have lingering
joint
pain, neurological problems, fatigue and heart problems.

Asthma is not strictly considered a seasonal disease because it can be
set
off by so many things, including dust mites, cockroaches, pet fur, mold
and
smoke, which are often worse indoors in winter. But it also has
summertime
triggers: pollen, ozone and exercise.

So what will happen this summer? Experts have only one answer: it
depends on
the weather. The C.D.C.'s maps detailing the spread of West Nile virus
look
terrifying. A tiny yellow dot over New York City in 1999 became, by
2003, a
spatter of red droplets crossing the Midwest like a biblical rain of
blood.
(Yellow means fewer than 100 cases per million people; red means more
than
100.)

West Nile virus peaked that year with 9,862 cases, of which 264 were
fatal.
The hardest-hit states formed a vertical stripe down the Great Plains,
from
North Dakota to Texas.

"That year was the perfect storm," said Dr. Lyle R. Petersen, director
of
the C.D.C.'s division of vector-borne infectious diseases. The virus,
moving
west in birds, hit the region for the first time, so no local bird was
immune to it. "Heavy rains in early spring created a huge population of
mosquitoes," he said. "Then it was an abnormally hot summer, which
produces
high levels of virus."

Contrary to popular wisdom, blue jays and crows are not important
carriers.
West Nile kills them quickly, and they are fairly big birds that hang
around
gardens and roads, so people notice when they die.

The most important reservoirs, say Dr. Petersen and Dr. Andrew
Spielman,
professor of tropical public health at the Harvard School of Public
Health,
are humble house sparrows. They develop high levels of virus without
dying.
They also roost together, so mosquitoes spread the virus quickly
through a
flock.

And they nest near houses, which is important, Dr. Petersen explained,
because the Culex mosquitoes that transfer the virus from bird to man
lay
their eggs in birdbaths and gutters and may travel no more than a block
in
their lives.

Four out of five people who get West Nile virus have no symptoms. The
other
20 percent have a fever, headache and fatigue. Sometimes, they get a
rash
and swollen glands. Less than 1 percent get severe complications like
neck
stiffness, stupor, convulsions or paralysis.

The best protection is anything that discourages mosquito bites:
screens,
DEET-based repellents and long pants, as well as draining standing
water in
the garden.

Birds that recover become immune, so there may never be a summer like
2003
again. But small birds like sparrows only live a couple of years, so
the
population becomes susceptible again.

"We may see very few infections for several years, and then a huge
outburst," Dr. Petersen said.

Lyme disease moves more slowly because it is spread by a spirochete
bacterium that lives in the digestive tracts of ticks that ride on deer
and
mice. Between Colonial times and the 1950's, deer living near people
risked
being eaten, so the northern deer tick, Ixodes scapularis, was driven
into
tiny pockets - the Elizabeth Islands off Massachusetts, Long Point in
Ontario and parts of Wisconsin, Dr. Spielman said.

But after World War II, with the growth of suburbs woodsy enough for
deer
but too populous for hunting, the disease began spreading. It was first
recognized in Lyme, Conn., and has since moved, with the deer, across
suburbia in much of New York, Massachusetts, New Jersey and
Pennsylvania.

It is still spreading, and the case count is generally increasing, said
Dr.
Ben Beard, chief of the bacterial zoonoses branch of the C.D.C. In
April, it
appeared for the first time in Chicago suburbs.

A worrisome aspect, Dr. Spielman said, is that babesiosis, a disease
caused
by a parasite in the same ticks, is spreading along the same routes as
Lyme
disease. Babesiosis is much less common than Lyme, but in rare cases
can
kill with malarialike fevers. The early signs of Lyme disease mimic the
flu - headache, fatigue, chills, fever and swollen lymph nodes. The
classic
sign - which not everyone gets - is a faint red "bull's-eye rash" that
appears around the tick bite, usually 3 to 30 days later, and spreads
slowly. A blood test can detect the infection.

Prevention is still the best medicine: avoid dry grass and brush and
piles
of dead leaves. Wear long pants tucked into socks, long-sleeve shirts
and
DEET repellent. Remove ticks promptly with tweezers because they often
feed
for 12 to 24 hours before injecting the bacteria.

Asthma has been so familiar for so long that it creates less fear than
it
probably should, given the number of people who die from it each year.

Predicting which area is at highest risk is impossible because pollen
counts
are local and soar up and down with the season, the breeze and the
rain.
However, the National Allergy Bureau, part of the American Academy of
Allergy, Asthma and Immunology, tracks pollen counts and even offers
e-mail
alerts.

Seasonal diseases do not mean that people should get scared, Dr.
Petersen
said. "These threats shouldn't alter people's plans for the summer -
they
should go out and enjoy themselves. But take precautions."

Copyright 2006 The New York Times Company

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