Control efforts continue to be directed at Culex stagnant water mosquitoes. Catch basins, detention/retention & building foundation (Villages are encouraged to report new building constructions to NWMAD) treatments are the predominant production areas. The District is finishing its third round of catch basin treatment with the insect growth regulator methoprene. Other stagnant water sites will be treated with the microbial insecticide Bacillus sphaericus.

Recent rains were not significant enough to produce a floodwater mosquito (Aedes vexans) egg hatch, however, even small amounts of precipitation will fill small containers less subject to evaporation and produce Culex mosquitoes. Homeowners are strongly urged to remove any stagnating water on their property that may produce these mosquitoes. Culex mosquito numbers start to increase this time of the season even under drought conditions. 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

Because West Nile virus (WNV) has been found in birds and mosquitoes in our District and Culex mosquito numbers are on the rise we have engaged our night spraying program. Targeted areas scheduled for August 2^nd would be Park Ridge, Des Plaines, Schaumburg & Palatine. For more detailed scheduling information regarding our night spraying program please call us at (847) 537-2306 and select phone menu option “5” to hear the schedule. The night spray schedule is updated by 3PM each day on the day we plan to spray. Future spray areas are based on detected WNV positive mosquitoes, birds and areas of high Culex mosquito trap counts based on our surveillance methods. All schedules are dependent on weather conditions.

WHY ARE WE SPRAYING AT NIGHT FOR MOSQUITOES WHEN IT HAS BEEN SO DRY AND THEY DON’T SEEM TO BE AROUND?

Since West Nile Virus has been detected in various areas throughout our District we have been spraying to reduce the Culex mosquitoes which are considered the primary mosquito capable of transmitting the virus to humans. The reason why people don’t normally notice this mosquito is because Culex primarily feed on the blood of birds and don’t normally prefer to bite humans. When numbers of these mosquitoes increase as they typically do into the late summer the chances that they may take a human blood meal also increases. Our Night Spraying Program helps reduce adult Culex numbers and it is the only practical method of controlling adult mosquitoes already infected with WNV and capable of transmitting the virus to more birds (amplification) or possibly humans.

MOSQUITO VIRUS SURVEILLANCE IN ILLINOIS

NWMAD has tested 240 Culex mosquito batches to date for West Nile Virus (WNV) and St. Louis encephalitis (SLE) using the VecTest. Nineteen mosquito batches have tested positive for WNV so far. WNV positive mosquitoes were from Arlington Hts, Glenview, Mt. Prospect, Northbrook & Wheeling thus far. Mosquitoes testing positive in the District will be posted in this Newsletter as well as the NWMAD website www.nwmadil.com.

DEAD BIRD SURVEILLANCE INFORMATION:

As of this writing 149 birds have tested positive for WNV in Illinois according to the Illinois Department of Public Health. Birds were collected from 40 counties in Illinois. 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.

FIRST WNV INFECTED HORSE IN ILLINOIS AND INCREASED RISK OF HUMAN CASES:

The Illinois Department of Public Health has reported the first WNV infected horse case from Madison County on July 22^nd. Horses appear to be sensitive to WNV and the number of severely affected cases are increasing dramatically in the southern states. The most significant aspect of WNV infected horses is that they are mammals like us and this is direct evidence that normally bird feeding Culex mosquitoes considered the primary vectors of WNV are now biting and transmitting the virus to a group of animals similar to humans. This would logically indicate that the risk of humans acquiring West Nile Virus may be increasing.

NOTE: Despite the tragedy (illness and fatalities) and sensationalism West Nile Virus has engendered since its introduction and spread throughout the U.S., the disease affects relatively few people compared to other notable/reportable diseases. Most people infected with the virus exhibit no symptoms of the disease at all, or, at most, flu-like symptoms, mild fever, headache, rash or swollen lymph glands. Less than 1% of the population develops encephalitis (swelling of the brain). Those most likely to develop encephalitis are the elderly and individuals with compromised immune systems (groups that definitely need to be educated about mosquitoes and WNV). Of those 1% more severely affected by the virus only 3-15% may result in a fatality.

DIRECTOR’S COMMENT: I feel it is important to understand that although the above note is true, based on epidemiological studies from New York City and elsewhere, one should not develop a false sense of security regarding the potential impact of this disease. For example, St. Louis encephalitis, also considered a rather rare encephalitis in humans and from the same family of viruses as WNV, under the right environmental/bionomic conditions caused over 500+ cases and 47 death’s in Illinois back in 1975. For this reason it is EXTREMELY IMPORTANT that cities, villages, health departments continue to publicize “MOSQUITO AVOIDANCE (between sunset & sunrise), STAGNANT WATER ELIMINATION, AND REPELLENT PROTECTION” to the Public.

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 5 days or longer like: tire casings, bird baths, flower pots 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 PLEASE FORWARD THIS INFORMATION TO APPROPRIATE DEPARTMENTS AND AGENCIES