West Nile Virus and Mosquito Control
Paper:
In a 2004 paper, West
Nile
Virus and Mosquito Control, PhD entomologist David
Pimentel of Cornell University writes that "Widespread ULV spraying
from ground equipment or aircraft for control of mosquitoes and West
Nile virus is relatively ineffective, costly, and has been
associated
with environmental and public health risks."
As to proper control, Pimentel writes "The prime
method of control is the elimination of the breeding habitats for
larval mosquitoes, such as water accumulating in bird baths,
flowerpots, old tires, and other containers."
Note that he writes "For effective mosquito
control,
at least 90% of the adults must be killed. Only a few scientific
studies of the effectiveness of spraying for mosquito control have
been
reported. These results are relatively discouraging. For example, in
Greenwich, CT, only a 34% mosquito population reduction was reported
after ground spraying, and in Houston, TX, only a 30% reduction
occurred after spraying.[6] Then in Cicero Swamp, FL, populations of
disease-carrying mosquito populations increased 15-fold after
spraying,[6] when the mosquito population was measured 11 days after
spraying. However, it is doubtful that the insecticide spray caused
the
increase in the mosquito population, but clearly the insecticide
provided insufficient adult mosquito control. . . . Also to be
considered are the serious public health and environmental problems
associated with the application of insecticides from aircraft"
Vector control officials and people taking
measurements in this
area are reporting 35% to 40% kill rates in cages, and lower
results are expected in the natural habitat. They clearly are
not
getting anywhere near the 90% figure Pimentel notes they must get
for
effective mosquito control.
Email:
In an email note he wrote the following when he
sent
a copy of this paper. We had called his attention to the Carney study
by
California Department of Public Health Officials:
"Thanks for your letter and the additional information. I have
a
few comments concerning this paper. First, before I comment I
should emphasize that I am not opposed to the careful use of
insecticides. My concern is that we use insecticides carefully
and we know what we are doing when we use insecticides and other
pesticides.
My comments concerning this paper are:
1) No mosquito population counts were made 5 days before and 5
days after spraying to assess the effectiveness of the
spraying.
2) Aircraft spraying is more effective than ground
spraying . . . It should be emphasized that only
10% to 25% of the insecticide applied by aircraft reaches the target
area, up to 90% drifts away from the target area and into the
environment at large. Clearly, the serious public health and
environmental problems associated with the application of
insecticides
need to be considered. There was no mention of these problems
in
the report.
3) I am not a statistician, but would like to know the type of
statistical analysis they used because they had only 1 control and 2
treatments. The 1 control is especially troubling.
. . . this is not a highly scientific assessment of the use of
insecticides in West Nile virus control. Mosquito control and
control of the diseases transmitted by mosquitoes is extremely
difficult. Pesticide treatments cost a great deal of money and
are hazardous to public health and the environment. Thus,
great
care needs to be exercised to make sure that public health and the
environment benefit from any insecticide treatment that is made."