Mosquito Control

Rebecca Brandt, Manager

810 Livingston Avenue
Bay City, Michigan 48708-6380
Voice: (989) 894-4555
Fax: (989) 894-0526

West Nile Virus

Background

West Nile encephalitis is a mosquito-transmitted disease first documented in North America during the summer of 1999.  The strain of West Nile virus (WNV) circulating in the U.S. causes significant mortality in exotic and native bird species, especially in the American crow.  WNV was first isolated in 1937 in the West Nile province of Uganda, Africa.  Epidemics have occurred in Africa, Europe, the Middle East, and most recently in Israel during 2000 and in the U.S. in 2002, 2003, and 2004, and 2012.  West Nile infections continued during the 2005-2017 seasons, and will most likely continue during 2018 (see table below for Bay County data).

The chance of anyone becoming infected with WNV is very low (less than 1% of mosquitoes are infected).  If infected, you would most likely show no symptoms or mild symptoms.  Mild symptoms include fever, headache, body aches, mild rash, and swollen lymph glands.  Severe symptoms may include severe fever, stiff neck, confusion, muscle weakness, and coma.  If you develop severe symptoms, contact your health care provider.

Human vaccines are still being developed and may be available in the future.  There is currently a single dose vaccine available for horses.

Dead Bird Reporting

Bay County Mosquito Control will be logging reports of dead birds (i.e., bird's location, including address, crossroads, and township; we'll also ask for the name of the person reporting the bird and a phone number).  While we are interested in collecting information about dead birds as part of our efforts to understand West Nile Virus (WNV), we will ONLY be collecting dead crows, blue jays, and ravens in good condition (no maggots or odor).  According to the Michigan Department of Community Health, other bird species (robins were recently implicated) also play a role in the persistence of WNV, but these species eventually clear the infection, and do not succumb to disease as often.  Not every crow, blue jay, or raven reported will be tested.  Birds will be collected from approximately May 15 through October 1.

Homeowners should report dead birds to Bay County Mosquito Control at (989) 894-4555.  Please report all birds, but species other than crows, blue jays, and ravens can be disposed of in the regular trash or buried.  When handling birds, avoid bare-handed contact.  Instead, turn a plastic shopping bag inside-out and scoop up the bird with the bag.  Place the bagged carcass in an outdoor garbage can for disposal.  We will not pick up live birds. Bay County Mosquito Control will test crows, blue jays, and ravens in our lab using a VectorTest kit. The results will be forwarded to the Michigan Department of Community Health and posted on the Emerging Diseases website www.michigan.gov/emergingdiseases.

The State of Michigan's website has a wonderful link that shows pictures of crows, ravens, and blue jays (the birds that can be tested for West Nile Virus) as well as other blackbirds that are often confused with crows.  If you are unsure of which bird species you have, please refer to this link.

We will not be involved in submitting any mammals.  However, should you find a sick or dead mammal displaying symptoms of West Nile virus (clinical signs prior to death may include uncoordinated flying or walking, weakness, lethargy, tremors, and abnormal head posture), please log onto the Emerging Diseases website (www.michigan.gov/emergingdiseases) and fill in the report.  Lack of funds will also impact the level of testing possible through the Michigan Department of Natural Resources for 2016.  MDNR staff will monitor the website year round.  Evidence of die-offs or unusual illness events in wildlife may prompt further investigation by MDNR biologists.  Questions about sick or dead wildlife can be directed to your local DNR office.  In the Saginaw Bay area, the closest field office would be the Bay City Customer Service Center at 3580 State Park Drive, Bay City, MI  48706  (989) 684-9141.

 

2018 West Nile Virus Bird Testing Results (By Zip Code)

 

Township or City

Zip Code

Number of Birds Tested

Birds Testing Positive

Auburn

48611


2

Bay City East/Hampton/
Portsmouth

48708

14

11

Bay City West/Monitor/
Bangor

48706

13

10

Bentley

48613

0

0

Essexville

48732

6

6

Kawkawlin

48631

1

0

Linwood

48634

0

0

Midland (Auburn)

48642

0

0

Munger

48747

0

0

Pinconning

48650

1

0

Rhodes

48652

0

0

 

Adult female mosquitoes are collected in a variety of traps:  New Jersey Light Traps, CDC Traps, and Gravid Traps.  The WNV mosquito season will run from May 15 through October 1. 

Some mosquitoes may be tested in-house by Bay County Mosquito Control staff, but most will be submitted to Michigan State University's Department of Microbiology and Molecular Genetics for analysis.  This year Culex species will be tested for West Nile virus and St. Louis Encephalitis because they are a known vector of those diseases.  Coquillettidia perturbans species, vectors of Eastern Equine encephalitis will also be submitted and analyzed.  Five hundred fifteen mosquito samples containing 18,160 female mosquitoes have been submitted for testing so far this 2018 season; five mosquito samples have tested West Nile Virus-positive.  Some results are still pending.

Besides mosquitoes, we also test birds (crows and blue jays), with results shown in the table above.  To date in Bay County, twenty-nine birds have tested positive for West Nile virus (twenty-six were either crows or blue jays tested at Bay County Mosquito Control and three were tested by the State), with an additional eight birds testing negative.  The additional three positives were reported to Bay County Mosquito Control from the Department of Natural Resources and included a West Nile virus- positive European starling from the south end of Bay City, an American Crow that tested positive for WNV in Bangor Township, and a West-Nile virus-positive Blue Jay from Monitor Township, all of which are accounted for in the table above.

As of September 14, 2018 in Michigan, there have been 9 counties with West Nile Virus positive mosquitoes, 149 mosquito pools testing positive for West Nile virus infection, 115 West Nile Virus bird cases, 44 human cases of West Nile with two fatalities, and 8 asymptomatic (no WNV symptoms) human blood donors (Sanilac - 1, Oakland - 2, Mackinac - 1, Kent - 1, and Wayne - 3 counties).  The 44 human cases originated in the following counties:  Wayne (20 cases), Berrien - 1, Oakland - 5, Allegan - 1, Ingham - 3, Macomb - 3, Monroe - 1, Kent - 9, and Other - 1.  The West Nile Virus fatalities occurred in Wayne and Kent Counties.

Steps people should take to protect themselves from mosquitoes include: 

  1. When outdoors, use insect repellent containing DEET, picaridin, or oil of lemon eucalyptus on exposed skin and/or clothing.  Always follow the directions on the product label.
  2. Stay indoors when mosquitoes are most active (dusk and dawn).
  3. Wear long sleeves and pants when weather permits.
  4. Have secure, intact screens on windows and doors to keep mosquitoes out.

Updated 9/19/18