Larvae of the floodwater mosquito (Aedes vexans) have been found. Cool temperatures have slowed the development of this nuisance mosquito. Some early-season snow pool adult mosquitoes (Aedes stimulans) have been observed, but, in relatively minor numbers. Egg rafts of Culex mosquitoes have also been collected earlier than normal. With recent (and coming) rains and above average rainfall totals nuisance floodwater mosquitoes may make their presence known by the end of the second week in May or sooner if median temperatures increase from what they currently are. Currently, crews are treating water areas containing mosquito larvae with the insect growth regulator methoprene. This season we are using a 150-day slow release methoprene briquette formulation in these areas so that our crews don’t have to retreat the same areas as frequently. These treatments will allow us focus control efforts on early stagnant water mosquito (Culex) development in an effort to further reduce the potential of bird-mosquito amplification of West Nile Virus.

MOSQUITO VIRUS SURVEILLANCE IN ILLINOIS

Dr. Linn Haramis, Manager of the Illinois Department of Public Health (IDPH) Arbovirus Surveillance Program reports that the State’s dead bird surveillance program for West Nile Virus (WNV) will begin May 1^st; only dead crows and blue jays will be accepted. Trapping and testing of wild birds for WNV, St. Louis (SLE) and Eastern Equine Encephalitis (EEE) will begin May 15^th. This year IDPH is using a different enzyme-linked immunosorbent (ELISA) assay and possibly also the hemagglutination inhibition (HI) assay for testing for arboviruses in birds. The state is planning to distribute the VecTest for testing mosquitoes for WNV & SLE to mosquito control organizations. More 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. The State’s website also has other valuable resource links on WNV, pesticides and mosquito control.

NWMAD will continue using the VecTest for detection of WNV and SLE in adult mosquito pools as it did in 2001.

2001 Arbovirus Surveillance in Illinois:

138 birds ® WNV

2 horses ® WNV

20 Culex mosquito pools ® WNV

Counties where WNV has been detected ® Cook, Lake, McHenry, Kane, DuPage, Will, Crawford

DEAD BIRD SURVEILLANCE:

NWMAD has not received any reports of dead birds.

Important: NWMAD will ship birds out for testing if requested (resources permitting) providing that the suspected birds are positively identified as crows or blue jays dead less than 48 hours. 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.

SUMMARY OF HUMAN CASES OF WEST NILE VIRUS IN THE U.S.

1999

62 cases of encephalitis (7 deaths).

2000

21 cases of encephalitis (2 deaths).

2001

50 cases of encephalitis (5 deaths).

NOTE: Despite the tragedy (illness and fatalities) and sensationalism West Nile Virus has engendered since its introduction and spread to 28 states in 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.

VACCINES FOR WEST NILE VIRUS:

To date there are no approved human vaccines for WNV though trial studies are forthcoming. A vaccine has been developed for horses but its effectiveness is still being evaluated. Vaccines for birds are also being developed and tested.

NWMAD WEBSITE:

The NWMAD website (www.nwmadil.com) is under construction. The Mosquito Update newsletter will also be available at this site as well as information on the history of NWMAD, personnel contacts, mosquito information links, employment opportunities and spray schedules.

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 7 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 7 days.

WEST NILE VIRUS SURVEILLANCE:

Please report any unusual incidences of bird deaths (especially crows & blue jays) to your local Health Department & NWMAD.

Mike Szyska

Director

PLEASE FORWARD THIS INFORMATION TO APPROPRIATE DEPARTMENTS AND AGENCIES.