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. West Nile infections continued during the 2005-2009 seasons, and will most likely continued during 2010 (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 1 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.
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.
For 2011, federal funds for WNV surveillance activities at the state level have been cut, forcing some changes to the way the disease is monitored in the state. Bay County Mosquito Control will test crows, blue jays, and ravens in our lab using a VecTest kit. The results will be forwarded to the Michigan Department of Community Health and posted on the Emerging Diseases website www.michigan.gov/emergingdiseases.
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 2011. 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 Operations Service Center at 503 N. Euclid Avenue, Bay City, MI 48706 (989) 684-9141.
2011 West Nile Virus Bird Testing Results
|
Township or City |
Zip Code |
Number of Birds Tested |
Number of Birds Testing Positive for West Nile Virus |
|
Auburn |
48611 |
1 |
0 |
|
Bay City East/Hampton/
Portsmouth |
48708 |
3 |
1 Positive Crow (9/6/11) |
|
Bay City West/Monitor/
Bangor |
48706 |
1 |
0 |
|
Bentley |
48613 |
0 |
0 |
|
Essexville |
48732 |
4 |
1 Positive Crow (9/1/11) |
|
Kawkawlin |
48631 |
0 |
0 |
|
Linwood |
48634 |
0 |
0 |
|
Midland (Auburn) |
48642 |
0 |
0 |
|
Munger |
48747 |
0 |
0 |
|
Pinconning |
48650 |
0 |
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 through mid-October.
Some mosquitoes will be tested in-house by Bay County Mosquito Control staff, but others will be submitted to Michigan State University's Department of Microbiology and Molecular Genetics for analysis. This year they will test Culex species for West Nile virus because they are a known vector of that virus as well as Coquillettidia perturbans species, vectors of Eastern Equine encephalitis. Other species that will be tested are Culiseta inornata and Aedes japonicus. As of 9/20/11, there have been 518 mosquito samples containing 9,912 females gathered throughout Bay County. Test results from MSU on all samples showed that 8 were positive (1.5%). Positive samples were found in Monitor and Pinconning Townships.
Besides the positive mosquitoes, we have also been testing birds (crows and blue jays), with results shown in the table above. To date, we have tested 9 birds and two have been positive. Nearby, Saginaw County has reported a WNV-positive crow and several mosquito samples from the Carrollton and Frankenmuth areas and the city of Saginaw. Furthermore, the Michigan Department of Community Health announced on 8-25-11 that a Macomb County man who recently died has been identified as Michigan's first 2011 human West Nile Virus case. To date, there have been a total of 29 human cases reported with 2 fatalities - 12 from Wayne County with 1 fatality, 7 from Macomb County with 1 fatality, 3 from Ingham County, 2 from Oakland County, 1 from Jackson County, 1 from Kent County, 1 from Eaton County, 1 from Shiawassee County, and 1 from Monroe County. Midland County, Arenac County, and Missaukee County have each reported the death of a horse from their respective counties as the result of a mosquito-carried infection of Eastern Equine Encephalitis virus.
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 10-18-11