NORTHWEST MOSQUITO ABATEMENT DISTRICT

147 W. Hintz Rd.

Wheeling, IL. 60090

Phone: (847) 537-2306

Fax: (847) 537-2583

www.nwmadil.com

 

Mosquito Update

June 30, 2005

 

WEST NILE VIRUS PRECAUTIONS URGED!

The lower numbers of human West Nile virus (WNV) cases during 2003-2004 in Illinois were most likely due to the unusually cool summers apparently unfavorable for human infections.   Generally, Flavivirus outbreaks like WNV and St. Louis encephalitis typically occur during hot, dry summers.  We are now experiencing weather conditions similar to that which occurred during the 2002 outbreak.  Human cases of WNV in Illinois also appear to increase whenever temperatures exceeded normal levels during the months of July, August and September.  Elevated temperatures and dry conditions appear to promote and accelerate WNV vector populations and/or transmission activities in Illinois.  We must not discount weather conditions that are similar to the 2002 outbreak season that may once again create conditions favorable for significant WNV activity. 

 

 

It is therefore, extremely important that residents eliminate stagnant water on their properties that may produce additional Culex mosquitoes and implement appropriate mosquito avoidance activities (see below) during the months of July-September.   Residents 50 years and older and individuals with compromised immune systems are especially susceptible to the more serious complications of WNV. 

 

DIRECTOR’S NOTE: During the 2002 WNV outbreak, communications with residents of NWMAD indicated that because nuisance flood water mosquitoes were at such low levels there may have been a COMMON MISPERCEPTION THAT THERE WERE NO MOSQUITOES BITING AT ALL!  Nocturnal mosquitoes like the Culex most frequently found infected with West Nile virus are commonly referred to as “SNEAKY BITERS” since their bite is very gentle and frequently goes unnoticed or may occur while people are sleeping.  Compounding this mosquito’s “sneaky” behavior is its predilection for seeking daytime resting areas inside or around houses ensuring closer contact and possible blood feeding on humans.  Residents should not be lulled in to a false sense of security and are STRONGLY advised to wear insect repellent and practice mosquito avoidance measures despite the seemingly mosquito-free conditions.  NWMAD gravid traps that collect Culex mosquitoes indicate that their populations are increasing at rates comparable to those seen in 2002.

 

PRESENT CONTROL STATUS:

NUISANCE MOSQUITO CONTROL

Nuisance mosquito numbers remain very low averaging in the single digits in our New Jersey light traps.  Control efforts and the ongoing dry spell are responsible for the low numbers. Nuisance mosquito biting will be extremely light if at all noticeable over the 4th of July holiday!  Residents, however, are strongly urged to remain vigilant about preventing mosquito bites (see below) during outdoor holiday activities between sunset and dawn since July is usually when we start to see human cases of WNV starting. 

 

Crews continue to treat any remaining floodwater areas with the microbial larvicide’s Bacillus thuringiensis israelensis (Bti) and Bacillus sphericus. 

 

CULEX MOSQUITOES

Culex mosquito numbers collected in our gravid traps have increased due to the warmer temperatures.  Elevated temperatures accelerate Culex development in stagnant water areas as well as the risk for WNV.   Residents are strongly advised to inspect & eliminate all stagnant water areas from their properties that may produce these mosquitoes every week through the months of July-September.  Any container that holds water and organic debris for greater than 7 days can produce many of these mosquitoes. 

 

Stagnant water mosquito producing sites (detention/retention ponds, ditches, building foundations & container sources) will be treated with the microbial insecticide Bacillus sphaericus and the insect growth regulator methoprene (a.k.a. Altosid).

 

ADULTICIDING (Night Spraying Operation):

No night spraying operations are currently planned at this time.  

 

Nightly spraying schedules can be viewed at the following website: http://www.nwmadil.com/District_map1.html.  Alternately, a recorded phone message describing our scheduled nighttime spray program can be reached at (847) 537-2306 and pressing “5” on your telephone keypad.   More information regarding our Adulticiding program may be viewed at: http://www.nwmadil.com/Night Spray info1.html

 

STREET & BACKYARD STORM SEWER TREATMENTS:

Street storm sewer and off-road catch basin treatments are complete.  Villages recently providing us with additional backyard storm sewer locations are in progress.  A second round of catch basin treatments is scheduled for July-August.

 

MOSQUITO VIRUS SURVEILLANCE IN ILLINOIS

NWMAD has tested (VecTest) 218 batches of mosquitoes for West Nile Virus, St. Louis and Eastern Equine encephalitis.   Two infected batches of mosquitoes were collected on 6/28 from Wheeling and Des Plaines gravid traps were positive for WNV via the District’s VecTest assay.  This is not unusual this time of the year based on previous WNV activity.  Samples will be shipped out for confirmatory testing by Illinois Natural History RT-PCR testing and additional Culex collections and testing follow-ups will be performed.

 

The Illinois Department of Public Health (IDPH) reports:  11 counties with mosquitoes or birds testing positive for WNV.  There are 8 WNV positive mosquito samples in Cook County from Evanston, Evergreen Park and Skokie.   Three WNV infected birds have been detected.

 

Mosquito batches testing positive in the District are posted at the NWMAD website http://www.nwmadil.com/VECTEST1.htm.

 

DEAD BIRD SURVIELLANCE INFORMATION:

NWMAD has received 136 dead bird (excluding 7 mammals) reports from Cities, Villages and the Public. 

 

Cities, villages and the public are encouraged to report dead birds to our District’s Dead Bird/Animal reporting web page, which can be accessed at www.nwmadil.com.  Knowing this information allows our District to better focus our control efforts.   The Cook County Department of Public Health is testing dead birds for WNV.  Anyone wishing to have recently dead crows and blue jays tested for virus should phone the Cook County Department of Public Health at (708) 492-2650

 

REDUCING THE RISK OF MOSQUITO BITES:

Avoid outdoor activity if possible from dusk to dawn when the mosquitoes bite the most.  If you do go out wear light colored protective clothing and insect repellent (always read label warnings and directions).  Make sure mosquitoes do not enter homes through unscreened or broken doors or windows.   Residents are encouraged not to create mosquito harborage areas.  Make sure tall grassy areas are trimmed and other vegetation is cut back.  If plants must be watered do so in the morning so the vegetation and soil has a chance to dry making it less attractive to mosquitoes.    Empty any containers holding stagnating water like tire casings, birdbaths, flowerpots and barrels that may produce mosquitoes. Un-maintained swimming pools may produce thousands of mosquitoes.  Call the District to report stagnant water areas that remain wet for more than 7 days.  Additional mosquito avoidance/control practices may be found at the District’s website: www.nwmadil.com.

 

Mike Szyska

Director

 

 

PLEASE FORWARD THIS INFORMATION TO APPROPRIATE DEPARTMENTS AND AGENCIES.