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August 31, 2012

Mosquito Populations Down From Previous Years

OSWEGO - Ongoing surveillance by the Oswego County Health Department shows that mosquito populations are down significantly compared to previous summers.

"We increased the number of mosquito trap sites over a greater area of the county this year," said Jiancheng Huang, public health director for the Oswego County Health Department. "Due in part to the relatively little snowmelt we had last winter and this summer's hot dry weather, the mosquito populations are down at each site."

So far this year, test results have indicated that the West Nile virus (WNV) was found in mosquito samples collected in Central Square, New Haven and West Monroe. It is also present in Onondaga County and areas of western and southern New York. An Oswego child has recovered from West Nile virus.

The Eastern equine encephalitis (EEE) virus, which claimed the life of an Oswego County girl last year, has not been detected in the county at this time.

Mosquito samples are routinely collected from trap sites around the county to test for the WNV and EEE. The results guide the county's response activities, from informing the public to aerial spraying.

"Aerial spraying is a partial and temporary control measure," said Huang. "It only decreases the mosquito populations for about one week, or a bit longer. After that, the numbers rebound back to where they were or sometimes even higher."

He added, "Spraying is not a silver bullet that you shoot once and rest for the whole season. It does not eliminate the viruses. We want residents to keep using personal protection measures even when spraying takes place."

The county works in consultation with the New York State Department of Health when making the decision to spray. A variety of factors are considered, such as the numbers and species of mosquitoes, infection rate and site locations, weather conditions and time of year, and the history and scientific data about the viruses.

"So far this year, conditions have not warranted the need for aerial spraying," said Huang. "If conditions change, we will re-consider this decision. Spraying is always regarded as an option."

Other issues that affect the decision to spray include the proximity of human population to positive mosquito pools and the potential harmful impact of the chemical spray on people, animals, other insect species, and the environment.

The Oswego County Health Department urges residents to continue to protect themselves and their families by taking the following precautions:

  • Use insect repellent properly. Those that contain DEET, picaridin or oil of lemon eucalyptus are most effective but should be used with care. Read the product label and use according to package instructions.

  • Limit outdoor activities in areas where mosquitoes are most active and between dusk and dawn which is the peak mosquito biting time.

  • If you have to be outside, wear long-sleeved shirts, long pants, shoes and socks as weather permits.

In addition, residents can follow these protective measures to minimize mosquito populations in and around their homes and properties:

  • Repair or replace all window and door screens to keep mosquitoes outside.

  • Reduce or eliminate all standing water from pails, recycling containers, wheelbarrows, wading pools, pool covers and similar water-holding containers.

  • Clear roof gutters, remove leaf debris from yards and gardens, and clean vegetation and debris from the edge of ponds.
  • Change the water in birdbaths and horse troughs twice a week.

  • Dispose of old tires at an Oswego County transfer station. There is a minimum $10 disposal fee. Contact the Oswego County Solid Waste Department at 591-9200 for details.

  • Use microbial control agents, or dunks, in contained sources of water such as abandoned swimming pools. Do not use dunks in areas where water sources flow together or in swampy regions.

The WNV and EEE are viral diseases that are transmitted to people through the bite of an infected mosquito. The risk of contracting either virus runs from June through September with peak activity late July to mid-August.

"These are different diseases caused by different viruses and transmitted by different mosquito species," Huang said. Most people infected with the WNV do not show any indication of the disease. Those who do may develop minor symptoms within 3 to 14 days after exposure. They include fever, headache, stomach ache, body aches, joint pain, vomiting, diarrhea and occasionally a skin rash and swollen lymph glands. The person's health usually improves after several days, but they may feel tired, weak and generally unwell for weeks.

Less than 1 percent of people infected will develop severe symptoms that affect the central nervous system. In rare cases, death can occur. Adults age 50 and older and people with certain medical conditions are at the greatest risk of developing serious symptoms. Most people recover will completely, even from a severe infection.

In contrast, EEE is a more rare and more often deadly disease. In the last 12 years, New York State has reported 490 human cases of the WNV with 37 fatalities as compared with only five reported human cases of EEE, all of which were fatal, since 1971.

Most people bitten by a mosquito infected with the EEE virus will not develop any signs; however, of those who do, symptoms usually appear 4 to 10 days later. They begin with a sudden headache, high fever, chills and vomiting. The illness may then progress into disorientation, seizures, coma or inflammation of the brain (encephalitis). It causes death in most cases; however, some people will survive the infection and have mild to severe brain damage for life.

Children under age 15 and adults over age 50 have the greatest risk for contracting the severe disease.

To learn more about mosquitoes and protecting your family against mosquito-borne illnesses, call the Oswego County Health Department at 315-349-3547 or 1-800-596-3200, ext. 3547, or visit the New York State Department of Health Web site at www.health.state.ny.us.


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