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Skip Navigation LinksDNREC : News : First finding of West Nile Virus for 2012 reported in DNREC Mosquito Control’s sentinel chickens

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

First finding of West Nile Virus for 2012 reported in DNREC Mosquito Control’s sentinel chickens

DOVER (Aug. 6, 2012) – West Nile virus has been detected in Delaware for the first time this year in a blood sample taken from sentinel chickens that are monitored for mosquito-borne diseases. The samples are collected as part of a statewide surveillance program conducted by DNREC’s Mosquito Control Section. No cases of West Nile virus (WNV) have been found in humans or horses so far in Delaware this year. 

The virus-positive results were reported to DNREC on Aug. 2 by the Delaware Division of Public Health Laboratory. The chicken was sampled at a monitoring station near Stanton on July 30, according to Mosquito Control Section Administrator Dr. William Meredith. Based upon these virus-positive findings, Mosquito Control will increase its mosquito population monitoring activities in the area and take appropriate mosquito control actions.  

Mosquito Control operates 24 caged chicken stations statewide. The sentinel chickens are humanely kept and tended in the field. If exposed to WNV or eastern equine encephalitis (EEE) viruses – both of which can affect humans and horses – chickens develop antibodies that enable them to survive. Their blood is tested every two weeks for these antibodies, which indicate exposure to these viruses.

West Nile virus was found in Delaware earlier this season through wild bird testing. Beginning July 8, three crows from New Castle County and one crow from Kent County have tested positive for WNV. As of the end of July, the Centers for Disease Control (CDC) had reported 241 West Nile human cases and four deaths nationwide, with Texas, Mississippi and Oklahoma having the most cases.

“The 2012 mosquito-disease transmission season is really only beginning, but preliminary indications suggest that 2012 might be a worse transmission year across the country than usual,” Dr. Meredith said.

“This finding of West Nile virus in Delaware serves 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 evening.”

Delaware Division of Public Health Director Dr. Karyl Rattay agreed with taking precautionary measures. "We know that insect bites are not only annoying and sometimes painful, but can be dangerous as well," Dr. Rattay said. "It's better medicine to prevent insects from biting you at all."

To reduce mosquito-breeding, people should drain or remove items that collect water, such as buckets or other 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, 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 added.

There are no approved WNV or EEE vaccines for humans. The majority of humans infected with WNV typically have symptoms similar to a mild flu, if they show any signs at all; 20 percent develop a mild illness which includes fever, body and muscle aches, headache, nausea, vomiting and rash. A very small percentage of patients, usually the elderly, develop severe neurological disease resulting in meningitis or encephalitis (inflammation of the brain). Symptoms may include sudden onset of severe headache, high fever, stiff neck, confusion and muscle weakness. Individuals with these symptoms should see their physician immediately. 

The worst year for WNV was in 2003, with 9,862 human cases and 264 deaths nationwide. That year, the worst West Nile outbreak in Delaware occurred, with 17 confirmed human cases and 2 fatalities, plus 63 horse cases.

Dr. Heather Hirst, State Veterinarian with the Delaware Department of Agriculture, said an effective equine vaccine now exists to protect horses from WNV and EEE. “I am urging horse owners to assist with prevention efforts by making sure their horses are vaccinated against both WNV and EEE,” Dr. Hirst said. “Initially, two doses of the vaccine are necessary for immunization. After the initial two vaccinations, a yearly booster is needed. Horse owners should consult their local veterinarian for advice on vaccination protocols. If horses have not been vaccinated or have only recently been vaccinated, owners should keep horses inside during peak mosquito times, i.e., dawn, dusk, and throughout the night.” 

To help determine when and where Mosquito Control Section services are needed, DNREC encourages residents to report intolerable numbers of biting mosquitoes by calling the numbers below. Staff answers phones between 8 a.m. and 4 p.m. Monday through Friday. Callers after business hours or during weekends or holidays should leave their name, phone number, address and a brief message. 

  • Glasgow Office, serving New Castle County and northern Kent County (including the Dover area): 302-836-2555
  • Milford Office, serving Sussex and southern Kent Counties: 302-422-1512

For more information about:

  • Mosquito biology/ecology and control – contact the Mosquito Control Section’s Dover office at 302-739-9917. 
  • WNV 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).
  • West Nile virus – visit the CDC website, 
Vol. 42, No. 295
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