September 24, 2003

PRESENT CONTROL STATUS:

Nuisance mosquitoes (Aedes vexans) continue to be low in the single digits from light traps. Given the predicted cooler temperatures and the shorter daylight hours Aedes vexans is not likely to be a problem for the rest of 2003.

Culex mosquitoes continue to be produced from stagnant water areas in the District but are greatly suppressed due to the cool temperatures. Crews continue to treat above ground stagnant water areas and have over the last 2 weeks begun re-treatment of catch basins starting on the East end of the District. Re-treatment of catch basins in this area is an additional step taken to help further reduce infected vector mosquito populations from returning to the same areas they have repeatedly appeared in over the last 3 years. Although aboveground mosquito production will disappear shortly Culex mosquitoes will continue to develop in subterranean stagnant water areas due to the warmer sustained temperatures in these, underground, protected habitats. Gravid trap counts have been mostly in the single digits, however, infected mosquitoes continue to be collected from Northfield, Wheeling and Maine Townships. Residents in the District are still cautioned to protect themselves from biting mosquitoes especially if warmer temperatures return. It is also important that residents prevent mosquitoes from entering their homes as mosquitoes may seek out warmer areas during the cool evenings. Culex mosquitoes do not die when the first hard frost arrives. Unlike the common nuisance mosquito, Aedes vexans, which dies off during hard frosts, Culex mosquitoes hibernate as adult mosquitoes during the winter months. Culex blood feeding activities lessen as daylight hours shorten and temperatures get cooler in autumn.

Homeowners should be strongly urged to remove any stagnating water on their property that may produce these mosquitoes. Virtually any water container (i.e. flower pots, garbage cans, pails, bird baths, un-maintained swimming pools, catch basins, etc) containing organic debris like leaves or grass can produce hundreds of these mosquitoes in about a week’s time during warm temperatures. Homeowners should also avoid watering lawns near open ditches or low areas that may cause water to accumulate in culverts under roadways.

ADULT MOSQUITO SPRAYING

Nighttime mosquito spraying has been suspended due to the low mosquito trap counts and the cool evening temperatures. Nightly spray schedules are available at our website www.nwmadil.com and updated by 3 PM each day. Alternately, residents can call us at (847) 537-2306 and listen to a schedule by selecting phone option “5” when they hear the recorded message.

NOTE: Adult mosquito spraying (adulticiding) may continue to be performed based on WNV surveillance activities and suitable weather conditions.

HUMAN CASES OF WNV

West Nile Virus in Illinois has struck nineteen humans thus far. See attached Illinois Department of Public Health news release. Seven of these cases occurred in Cook County. One of the human cases occurred in Rolling Meadows but health officials suggest the case was acquired in Colorado where that person was present during the predicted infection period. Colorado now leads the nation in human infections so far in 2003. Additional mosquito trapping is being conducted in Rolling Meadows after the human case was announced. All mosquitoes tested negative via the VecTest. It is likely that more human cases of WNV will be released since peak infected mosquito activity in Northwest Cook County occurred during the last 2 weeks of August and it may take IDPH almost a month to confirm cases.

MOSQUITO VIRUS SURVEILLANCE IN ILLINOIS

NWMAD has tested 949 Culex mosquito batches to date for West Nile Virus (WNV), St. Louis encephalitis (SLE) and Eastern Equine encephalitis (EEE) using the VecTest. 68 mosquito batches have tested positive for WNV so far. Mosquitoes testing positive in the District are posted on the NWMAD website http://www.nwmadil.com/VECTEST1.htm

DEAD BIRD SURVIELLANCE INFORMATION:

As of this writing 698 dead birds have have been reported to our website. NWMAD dead bird report website can be accessed at: http://www.nwmadil.com/Dead Birds.html Current information about WNV can be found on the state’s website www.idph.state.il.us/envhealth/wnv.htm or by calling 217-782-5830.

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, loose fitting, 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 unnecessary 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 for 7 days or longer like: tire casings, birdbaths, flowerpots and barrels that may produce mosquitoes. Neglected swimming pools may produce thousands of mosquitoes. Call the District to report large stagnant water areas that remain wet for more than 7 days.

Mike Szyska

Director

September 24, 2003

ADULT MOSQUITO SPRAYING

HUMAN CASES OF WNV

PLEASE FORWARD THIS INFORMATION TO APPROPRIATE DEPARTMENTS AND AGENCIES