Insecticides to Curb West Nile Best Choice?

  • The Culex pipiens quinquefasciatus mosquito - one of the mosquitoes responsible for the transmission of West Nile virus. (Photo courtesy of the USGS.)

Some health experts and politicians are struggling with balancing the risk of West Nile virus with the perceived hazards associated with spraying insecticides to kill the mosquitoes carrying the virus. The big question is – to spray or not to spray? Last year… public health officials in many communities decided to spray pesticides on adult mosquitoes, hoping to reduce the chance of West Nile virus infection in humans. But spraying was met by a public outcry from some residents concerned about the immediate and possible long-term health effects of the chemicals. This year, some health departments have chosen to focus their control efforts on killing mosquito larvae before they hatch with chemicals that are relatively benign. Others still plan to spray. The Great Lakes Radio Consortium’s Karen Schaefer reports:

Transcript

Some health experts and politicians are struggling with balancing the
risk of West Nile virus with the perceived hazards associated with spraying
insecticides to kill the mosquitoes carrying the virus. The big question is –
to spray or not to spray? Last year… public health officials in many
communities decided to spray pesticides on adult mosquitoes, hoping to reduce
the chance of West Nile virus infection in humans. But spraying was met by a
public outcry from some residents concerned about the immediate and possible
long-term health effects of the chemicals. This year, some health departments
have chosen to focus their control efforts on killing mosquito larvae before
they hatch with chemicals that are relatively benign. Others still plan to
spray. The Great Lakes Radio Consortium’s Karen Schaefer reports:


Last year there were more than 4,000 reported cases of West Nile virus
in the United States. The virus hit some Great Lakes states especially
hard. In Ohio, in Cuyahoga County – which surrounds Cleveland – 211 cases
were confirmed and 14 people died. The County’s health district decided to
do a sero-survey, taking blood samples from about 1200 residents to
find out just how many people actually got West Nile virus without noticing
any symptoms. Assistant Administrator Terry Allen says the results were
surprising.


“We found that between four and about six and a half-percent of
residents were exposed to West Nile virus. That equates to perhaps 50 to
80,000 people in Cuyahoga County that were exposed last year.”


Allen concedes that one way of looking at those figures is to see that the
number of deaths in the infected population was extremely low. But Allen is
concerned that a new outbreak of West Nile could infect thousands of people
who weren’t exposed last year and could cause even more deaths. So he says
the county has decided to take all possible precautions – including spraying
a pesticide on adult mosquitoes in areas where human cases are reported.


“You have to put this in context. Most counties in Ohio do not
spray for mosquito control.”


That’s Barry Zucker, president of the Ohio Coalition Against the Misuse of
Pesticides. He’s one of many county residents who oppose spraying.


“What the doctors tell us and what the medical studies tell us
is that there are real and potential health consequences from pesticides –
everything from upper respiratory diseases to possible neurological damage
to possible increase in breast cancer. The bottom line is that the pesticide
spraying for adult mosquitoes does not work.”


Others have come to the same conclusion. Bill Tomko is president of the
village council of the Cleveland suburb of Chagrin Falls.

“Our concerns relative to the county board of health was they
didn’t really have any data that indicated that the spraying would do any
good. And we became quite concerned that it was being done to have the
appearance of action in order to quell the emotional response of, you
know, ‘Do something, protect me.'”


Tomko say his community is one of many in the region that have decided not
to spray.


“My first reaction is just to extrapolate from the medical
profession when you’re looking at spraying versus not spraying, first do no
harm. The better way to do it is to apply individual protection
measures and to go after the breeding of the mosquitoes themselves, which is
what we adopted to do in Chagrin Falls by adopting a larvacide program.”


Tomko says his community will pepper catch basins and areas of standing
water with a chemical briquette that kills only mosquito larvae. Combined
with a reduction of breeding sites like removing old tires, continued
surveillance, and a public information campaign about the need for personal
protection, Tomko hopes to keep residents safe from infection by West Nile
virus. Last year, no one in Chagrin Falls got sick.


But Cuyahoga County Health Director Tim Horgan says, with the high infection rate seen
last year in urban areas, he just can’t take that risk. So in addition to larvacide,
surveillance, and all the rest, he says the county will use pesticide sprays
if conditions warrant. Health Director Horgan warns that even residents on
the county’s no-spray list could see pesticide spraying in their
neighborhoods this summer.


“With the problems we had last year, we might have areas where’s
there’s a number of houses on an individual street where people would rather not be
sprayed. And then we might have a case or two of human disease right in that area. If
that happens to us this year, we’re going to notify people on the list, let them
know we’re going to be there. But I think we’re going to try to go in and
make sure that area gets sprayed and that’s very consistent with the
recommendations of the CDC.”


But even the head of the Centers for Disease Control admits there’s not
enough good scientific evidence to be sure spraying works. So while some
health districts such as Cuyahoga County and the city of Cleveland plan to
spray, Chagrin Falls and many other communities do not. What all health
officials do agree on is that avoiding getting bitten is the best way to
keep West Nile at bay.


For the Great Lakes Radio Consortium, I’m Karen Schaefer in Cleveland.

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