Continued cooler than average temperatures have greatly delayed floodwater mosquito development. This delay has allowed our crews ample time to treat most all our floodwater areas and keep mosquitoes low. Light trap counts have averaged in the single digits below our threshold for adult mosquito spraying. Rains last week have produced another floodwater mosquito brood but our residual methoprene treatments should continue to minimize their development. Stagnant water Culex mosquitoes have been increasing in numbers based on trap counts. Catch basin treatment for Culex mosquito control has gone into full swing throughout the District. Likewise, other Culex production areas such as ditches, retention/detention ponds, tires, building foundations and other stagnant water areas continue to be treated in the District.

Biting adult mosquitoes have been reported from residents located near heavily forested areas. These appear to be the floodwater mosquito (Aedes vexans) which is not currently considered a significant vector for West Nile Virus transmission by health authorities. We continue to monitor adult mosquito numbers in these areas but have not seen any sustained significant elevations in our New Jersey light traps. Currently there are no plans to perform adult mosquito night spraying unless trap counts and temperatures increase, or Culex mosquito numbers become excessive or WNV activity becomes prevalent in birds and/or WNV positive mosquito pools are detected. Larval mosquito control and virus surveillance in mosquitoes remains our primary focus.

MOSQUITO VIRUS SURVEILLANCE IN ILLINOIS

NWMAD has tested 41 Culex mosquito pools to date for West Nile Virus and St. Louis encephalitis. All pools tested have been negative to date. Although cool temperatures have suppressed Culex numbers we have managed to collect enough mosquitoes for testing from the following municipalities: Arlington Heights, Barrington, Bartlett, Des Plaines, Elgin, Mt. Prospect, Palatine, Northbrook & Park Ridge. Mosquito pools testing positive in the District will be posted in this Newsletter as well as the NWMAD website www.nwmadil.com.

DEAD BIRD SURVIELLANCE INFORMATION:

As of this writing 8 birds have tested positive for WNV in Illinois according to the Illinois Department of Public Health. Birds were collected from Clark (1), Cook (3), Edgar (2), Kane (2) counties. More/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.

Cook County Department of Health is coordinating dead bird collections. Health Departments should contact the WNV Program Manager LaTrice Porter-Thomas (708-492-2035) if they wish to submit dead birds for testing or have any questions regarding surveillance practices. As before, residents of the District should first contact their local Health Department if they find a dead blue jay or crow.

Important: NWMAD will hold birds for testing if requested (resources permitting) providing that the suspected birds are positively identified as crows or blue jays dead less than 48 hours and the local municipality health department has contacted Cook County about the dead bird submission. Note: the state is no longer collecting raptors (i.e. hawks) or birds other than crows & blue jays for testing. Local health departments should refer to the memorandum from Carl W. Langkop, Chief Communicable Disease Section, and Linn Haramis, Program Manager Vector Control/Arbovirus Surveillance (IDPH) for bird submission details.

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 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 stagnant water areas that remain wet for more than 5 days.

Mike Szyska

Director

PLEASE FORWARD THIS INFORMATION TO APPROPRIATE DEPARTMENTS AND AGENCIES.

Memorandum

Date: June 17, 2002

To: Municipal Governments and Local Health Departments

Re: Mosquito Control and Prevention of West Nile Viral Encephalitis

From: Linn David Haramis, Ph.D., Entomologist / Vector Control Program Manager

Illinois Department of Public Health, Division of Environmental Health

525 W. Jefferson St., Springfield, IL 62761

217‑782‑5830, Fax: 217‑785‑0253, LHARAMIS@IDPH.STATE.IL.US

During 2001, mosquito-borne West Nile virus was first reported from dead birds in Illinois. More than 130 West Nile virus positive birds were collected in northwestern Illinois. The appearance of West Nile virus in densely-populated northeastern Illinois resulted in local health departments expending many staff-hours in responding to inquiries by concerned citizens. Additionally, there was intense interest in the issue by citizens and the news media.

On May 5, 2002, the first West Nile virus positive crow was reported from Kane County. Since then, additional West Nile virus positive birds have been reported from northeastern Illinois and Edgar County in south-central Illinois. Although the Department has been testing wild birds for mosquito-borne St. Louis encephalitis virus since 1976, this is the first time in years that several arbovirus positive birds have been detected early in May. Additional information about West Nile virus may be found on the Department’s web site: < http://www.idph.state.il.us/envhealth/wnv.htm >.

Because of concern about a possible outbreak of West Nile viral encephalitis like that which occurred in New York City in 1999, some communities have begun or increased mosquito control programs. Consequently, Department staff believe that local governments that conduct mosquito control programs should emphasize the methods that are most effective at controlling the primary mosquito vectors (carriers ) of West Nile virus and a related disease, St. Louis encephalitis virus.

Please be aware that all personnel who do pesticide applications for mosquito pest control must be licensed by the Illinois Department of Agriculture (IDA). The only exceptions are if one sprays one’s own residential property and for certain insecticides used by tire recycling companies to treat water-filled used tires. Please contact the IDA at 217-785-2427 for more information about mosquito control licensing.

Control of the West Nile Virus Mosquito Vector

Control of Culex Larvae is a Priority - Although West Nile virus has been detected in several species of mosquitoes, about 70% of the positive samples have been from Culex pipiens (the house mosquito) and related species of Culex. The house mosquito breeds most prolifically in stagnant water that has a heavy organic content. In urban areas, street catch basins, artificial water-filled containers like used tires and poorly-draining ditches are common production sites for Culex mosquitoes. Additionally, most of the house mosquitoes present in a community were produced locally because the house mosquito does not fly more than about 1 to 2 miles from its production site. In contrast, the inland floodwater mosquito (Aedes vexans) can fly 10 or more miles from where they hatch, particularly along prevailing winds. Floodwater mosquitoes have not been significant disease carriers in Illinois and are currently believed to be minor carriers of West Nile virus.

The most effective method of mosquito control is “larviciding” or the treatment of locations where mosquito larvae are present such as the water impounded in the bottom of street catch basins. Because street catch basins are a primary source of the house mosquito, the Department recommends that catch basins be treated at least twice during the summer to control Culex mosquitoes. Ideally, municipalities should treat catch basins and other locations that produce Culex mosquitoes as often as determined by necessary inspection and according to insecticide label directions. However, a minimum response by a municipality would be to treat catch basins and other Culex production sites twice during the summer (June and July). This would reduce numbers of vector mosquitoes during late summer, the period of greatest risk to humans. Please see Table 1 for a list of mosquito larvicides.

Spraying for Adult Mosquitoes is Transitory - Adult mosquito control (also called “fogging” or “spraying”) is the method of mosquito control that is most familiar to the public. However, the aerosol fog kills only mosquitoes that contact insecticide droplets; the fog soon dissipates. Although the local mosquito population is reduced for a few days, fogging does not prevent mosquitoes from re-entering the area. Because only a part of the local adult mosquito population is reduced only for a few days by fogging, municipalities should give priority to larval mosquito control of Culex mosquitoes.

Nonchemical Mosquito Control ‑ Mosquito larvae or "wrigglers" must live in still water for five or more days to complete their growth before changing into adult biting mosquitoes capable of transmitting disease. Often, the number of mosquitoes in an area can be reduced by removing sources of standing water. Hundreds of mosquitoes can come from a single discarded tire. Local agencies should inform the public about how to prevent mosquito production around residences:

· Get rid of old tires, tin cans, buckets, drums, bottles or any water‑holding containers.

· Fill in or drain any low places (puddles, ruts, etc.) in the yard.

· Keep drains, ditches, and culverts free of weeds and trash so water will drain properly.

· Keep roof gutters free of leaves and other debris.

· Cover trash containers to keep out rainwater.

· Repair leaky pipes and outside faucets.

· Empty plastic wading pools at least once a week and store indoors when not in use. Unused swimming pools should be drained and kept dry during the mosquito season.

· Fill in tree rot holes and hollow stumps that hold water.

· Change the water in bird baths and plant pots or drip trays at least once each week.

· Store boats covered or upside down, or remove rainwater weekly.

· Keep grass cut short and shrubbery well-trimmed around the house so adult mosquitoes will not hide there.

In summary, local agencies that conduct mosquito control should give highest priority to eliminating breeding sites and larviciding. Preventive larvcidal treatment of Culex production sites will help municipalities protect Illinois citizens from mosquito-borne diseases. Additional references about mosquito control may be found in Table 2.

Table 1. Mosquito Larvicides Commonly Used in Illinois ¹

Note: Mosquito larvicides with methoprene or Bacillus sphaericus as the active ingredient have been found to be particularly effective for control of Culex mosquito larvae in catch basins.

Larvicide

Type

Action

Primary Use

Abate^R (Temephos)

Organophosphate

Directly toxic

Containers, floodwater sites

Altosid^R (Methoprene)

Growth regulator

Prevents larvae from developing to adults

Catch basins, containers, floodwater sites

Bacillus thuringiensis

israelensis (Bti)

Bacterial

Gut toxin

Floodwater, catch basins

Bacillus sphaericus (Bs)

Bacterial

Gut toxin

Catch basins, septic

waters (for Culex)

Oils (Golden Bear^R & BVA^R) ²

Surface treatment

Suffocation: film covers air tubes of larvae

Floodwater, catch basins,

septic waters

¹ Always read and follow all current pesticide label instructions. If any information in these recommendations disagrees with the pesticide label, the label instructions must be followed. Use of a product name does not constitute product endorsement. All pesticides must be registered with USEPA and the Illinois Department of Agriculture.

² Monomolecular film larvicide (Agnique^R , an alcohol-derived product) that acts like an oil larvicide has become available recently.

Table 2. Mosquito Control References

Agency

Title

Web Site Address

IDPH

Mosquitoes

www.idph.state.il.us/public/hb/hbmosquito.htm

Prepared News Releases about Mosquito Prevention (PDF file)

www.idph.state.il.us/envhealth/pdf/mosquito‑borne01.pdf

DEET Insect Repellents

www.idph.state.il.us/envhealth/deetfacts.htm