THE DESPLAINES VALLEY MOSQUITO ABATEMENT DISTRICT does not conduct routine
adult mosquito control operations. Adult mosquito control is the least effective approach to
mosquito control with only localized, temporary benefits. When excessive numbers of adult
nuisance mosquitoes are experienced, harborage adult mosquito control will be conducted as
described below. However, adult mosquito control is the only tool available to use against an
adult mosquito population which is involved in disease transmission. Hence, the District will
only implement residential adult mosquito control operations as a contingency measure for
disease vector mosquitoes when there is significant risk of mosquito-borne disease
transmission.
Harborage Adult Mosquito Control
When excessive numbers of adult Aedes vexans and related nuisance species of mosquito are
experienced due to migrations from outside the District's area, adult control measures are
conducted within specific harborage areas. Harborage areas are defined as densely
vegetated or wooded areas typically outside of residential areas where adult mosquitoes rest
or harbor and are concentrated in numbers prior to continued migration. Such harborage
areas include vegetated swamps and numerous wooded areas along flood plains, the Sanitary
Drainage & Ship Canal, the I & M Canal, Des Plaines River, and several creeks. Areas within
the Cook County Forest Preserve District are not included in this operation per their request.
Adult control measures would focus on hot spots experiencing problems. Harborage site
treatment is conducted during the dawn hours when sufficient daylight is present to negotiate
off-road terrain typically encountered in harborage areas, yet satisfy temperature and wind
criteria permitted for adult control operations.
Residential Adult Mosquito Control
The District considers guidelines established by the Illinois Department of Public Health (IDPH)
in their publication entitled "IDPH Surveillance and Response Procedures for Mosquito-borne
Arbovirus Emergencies" and the Center for Disease Control in consideration of residential
adult mosquito control operations. Operations will be focused against specific vector
populations of Culex pipiens and related species in an effort to minimize or break a viral
transmission cycle.
Specific criteria considered to initiate residential adult mosquito control are as follows:
Primary Triggers
a) POSITIVE MOSQUITO POOLS - Confirmation of viral activity within the adult mosquito
population. Our District operates a network of gravid traps to collect adult mosquito samples
for subsequent testing of West Nile Virus(WNV) & St. Louis Encephalitis(SLE). These traps are
highly selective in collecting Culex species mosquitoes having had a blood meal and potential
exposure to WNV or SLE. In-house testing using the VecTest process gives immediate results
which are further sent to the Illinois Natural History Survey (INHS) for confirmation utilizing
alternate tests.
b) Dead Birds - Numbers of dead crows/blue jays/raptors and the time of year they are found.
Subsequent confirmation by the IDPH of WNV within the dead birds.
c) Time of Season - The point in any given mosquito season when initial positive bird and
mosquito pool samples are confirmed. Positive samples early in the season set the stage for a
developed viral amplification/transmission cycle, whereas initial positive samples late in the
season would minimize this cycle.
d) Surrounding State Data - Viral activity in adjacent states, particularly early in the season, is
a precursor to activity in our state.
e) Equine Cases - Confirmed equine(horse) cases are an indicator that a spillover from the
bird population has occurred. Viral activity has amplified and escalated to a level where this
occurs.
f) Human Cases - Confirmed human cases or fatalities are the ultimate indicator that a
spillover from the bird population has occurred, and is likely to continue.
Secondary Triggers
a) Vector Population Level - A larger than normal vector population level poses a greater risk
for spillover disease transmission to humans. But a low vector population does not imply that
disease transmission will be minimal or disappear. Under the circumstances of a high infection
rate, spillover transmission will occur even with a low vector population.
b) Weather: Rain & Temperature - Rainfall can directly affect vector population levels. Water
is required for all mosquito development, with rainfall influencing the number of potential
breeding sources. Temperature on the other hand can affect both vector population levels
and the viral amplification/transmission cycle. Above normal temperatures also can increase
the viral transmission rate.
Insecticide used for adult mosquito control
The insecticide used is Anvil 10+10 ULV, a synthetic pyrethroid. It is manufactured by
Clarke Mosquito Control Products, Inc.
