| Mosquito
scientist probes spread of West Nile. The
work of a Harvard University researcher,
who studied mosquitoes years before
anyone in North America had ever heard
of West Nile virus, may yield some clues
about why the disease is spreading so
quickly.
Dr.
Andrew Spielman, a professor of tropical
public health at Harvard University's
department of immunology and infectious
disease, has studied one of the most
common seasonal pests since 1948 -- 50
years before the first case of West Nile
virus would reach North America.
Back
then, people had heard of illnesses like
malaria and dengue, which are also
spread by mosquitoes. But in North
America, Spielman's work seemed to have
little relevance to urban life.
Now,
with 307 confirmed and 83 probable cases
of West Nile in Canada and thousands in
the U.S. last year, his research is
taking on a startling significance.
"Yes,
the work that had no practical
importance now has intense practical
importance," Spielman told CTV
News.
Spielman
spends his time searching Boston's
subterranean world -- subway tunnels and
sewers -- for hibernating mosquitoes.
The Harvard researcher believes some of
the sleeping insects already carry the
virus. That would explain why West
Nile survives the winter and
returns each summer.
The
question that most intrigues Spielman is
how these mosquitoes pick up the virus
themselves.
Scientists
have long held that the insects pick up
West Nile by biting infected birds. But
because the hibernating mosquitoes are
newly hatched and wouldn't have a chance
to be exposed to infected birds, the
question of the source of exposure
remains.
"If
the only way that a mosquito can become
infected is by feeding on an infected
bird or animal -- what in the world is
happening? How are we getting infected
mosquitoes?" says Spielman.
"We don't have the answer. It's
just a fascinating situation."
All
across the continent, scientists are
trying to find the answer. So far, West
Nile has only been found in dormant mosquitoes
twice, most recently in Pennsylvania.
But
the fact that West Nile has been found
in these sleeping insects leads
researchers to speculate that the virus
is passed on from mosquito to mosquito,
likely through the eggs. This means when
infected mosquitoes lay their eggs, the
offspring are automatically infected.
"The
bottleneck is in the winter hibernation.
It's the critical stage that determines
success or failure of those house
mosquito population," says Spielman.
"If we understood more about the
mechanism of hibernation and the various
influences of climate I think we might
at least understand the epidemiologist
of this infection and why one year might
be a severe year and another not."
For
example, Spielman says this year, his
researchers have found surprisingly few
hibernating mosquitoes -- possibly
because it was too warm last August for
the insects to hibernate successfully.
"Would
that ever be interesting, if this next
year was a poor year for West
Nile," says Spielman.
The
ultimate goal is to reduce mosquito
transmission of West Nile to humans,
possibly by tricking mosquitoes into
coming out of hibernation early so they
don't survive the winter.
"We
can certainly do that in the lab. The
question is, whether it's
practical," Spielman says.
|
