DNREC Mosquito Control Section announces year’s first findings of West Nile and equine encephalitis viruses

Date Posted: Thursday, August 10th, 2017
Categories:  Division of Fish and Wildlife DNREC

DOVER – The Department of Natural Resources and Environmental Control’s Mosquito Control Section, in conjunction with the Delaware Division of Public Health Laboratory and the Department of Agriculture, announced today the first detection of mosquito-transmitted viruses in Delaware this year reported earlier this month. West Nile virus (WNV) was recently detected along the Delaware River in the Wilmington area and in west-central Kent County – both instances confirmed by blood samples taken from DNREC’s sentinel chickens. Eastern equine encephalitis (EEE) has also recently been detected from a sentinel chicken in southwestern New Castle County. Additionally, a WNV-positive wild crow was recently found in northwestern New Castle County. Thus far in Delaware this year, no cases of WNV or EEE have been found in humans or horses.

“These findings are not cause for alarm, but are of some concern,” said Mosquito Control Section Administrator Dr. William Meredith, Division of Fish & Wildlife. “Based on these virus-positive findings, and with mosquito season reaching its peak for transmission of mosquito-borne diseases from about mid-August into mid-October, Mosquito Control will increase its mosquito population monitoring activities in targeted areas, and continue to take appropriate control actions as warranted.”

DNREC’s Mosquito Control operates 20 monitoring stations with caged chickens statewide. The sentinel chickens are humanely kept and tended in the field. Sentinel chickens bitten by mosquitoes carrying WNV or eastern equine encephalitis (EEE) – both of which can affect humans and horses – develop antibodies that enable them to survive. Their blood is tested every two weeks for the antibodies, which indicate exposure to the mosquito-borne viruses.

The Mosquito Control Section also conducts extensive statewide monitoring to determine the types and population abundance of 19 problematic mosquito species through a statewide network of more than 30 stationary adult light trap stations. The Section also assesses larval mosquito populations by sampling aquatic habitats around the state.

There are no approved WNV or EEE vaccines for humans. The majority of humans infected with WNV will not show any symptoms; 20 percent develop a mild illness which may include fever, body and muscle aches, headache, nausea, vomiting, and rash. A small number of humans who are infected develop serious illness, particularly certain groups who are more vulnerable, such as senior citizens. Neurological symptoms including paralysis and possibly death may occur.

“The first findings of mosquito-transmitted viruses in Delaware this year serve as a good reminder for people to take common-sense precautions against mosquito bites,” Meredith said. These include wearing long-sleeved shirts and long pants when outdoors in mosquito-prone areas, applying insect repellent containing 10-30 percent DEET in accordance with all label instructions, and avoiding mosquito-infested areas or times of peak mosquito activity around dusk, dawn or throughout the night.

To reduce mosquito-breeding habitat and chances of disease transmission, residents should drain or remove from outdoor areas all items that collect water, such as discarded buckets or containers, uncovered trash cans, stagnant birdbaths, unprotected rain barrels or cisterns, old tires, upright wheelbarrows, flowerpot liners, depressions in tarps covering boats, clogged rain gutters, corrugated downspout extenders and unused swimming pools. “The possibility of mosquito-borne disease transmissions won’t subside until cooler autumn temperatures set in, usually in mid-October and sometimes even later,” Meredith said.

For more information about:

  • Mosquito biology/ecology and control – contact the Mosquito Control Section’s Dover office at 302-739-9917.
  • Reporting WNV-suspect wild birds, or for requests for mosquito relief – for upstate areas from Dover north, contact Mosquito Control’s Glasgow field office at 302-836-2555; for downstate areas south of Dover, contact Mosquito Control’s Milford field office at 302-422-1512.
  • WNV or EEE in humans and related medical issues – contact the Delaware Division of Public Health at 888-295-5156.
  • WNV or EEE in horses and equine vaccines – contact the Department of Agriculture’s Poultry and Animal Health Section at 302-698-4500 or 800-282-8685 (Delaware only).
  • For more information on West Nile Virus or Eastern equine encephalitisvisit the CDC website.

Media Contact: Joanna Wilson, DNREC Public Affairs Office, 302-739-9902

DNREC Logo The Delaware Department of Natural Resources and Environmental Control (DNREC). Want your news hot off the press? Join the DNREC press release email list. Send a blank email to
For more information, contact the DNREC Public Affairs Office, at 302.739.9902

The Division of Fish & Wildlife conserves and manages the fish and wildlife resources of the state, including restoration of habitats, and provides safe fishing, boating and hunting opportunities. Follow the Division on FaceBook.

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