Contact: Joanna Wilson, DNREC Public Affairs, 302-739-9902
First finding of West Nile Virus for 2013 reported
in DNREC Mosquito Control’s sentinel chickens
DOVER (July 29, 2013) – West Nile virus (WNV) has been detected in Delaware for the first time this year in blood samples taken from DNREC’s sentinel chickens that are monitored for mosquito-borne diseases. The samples are collected as part of a statewide surveillance program conducted by DNREC’s Division of Fish and Wildlife Mosquito Control Section. No cases of West Nile virus have been found in wild birds, horses or humans so far in Delaware this year.
The virus-positive results were reported to DNREC on July 26 by the Delaware Division of Public Health Laboratory. The chickens were sampled at monitoring stations near Leipsic on July 22 and Georgetown on July 23, 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 these areas and take appropriate mosquito control actions.
Mosquito Control operates 24 monitoring stations with caged chickens statewide. The sentinel chickens are humanely kept and tended in the field. Sentinel chickens bitten by mosquitoes carrying WNV, eastern equine encephalitis (EEE) or St. Louis encephalitis viruses – all of which can affect humans and horses – develop antibodies that enable them to survive. Their blood is tested every two weeks for these antibodies, which indicate exposure to these viruses.
According to Dr. Meredith, it’s somewhat unusual in Delaware to first find occurrences of WNV during any given year in sentinel chickens and not in wild birds, and also in downstate locations in Kent and Sussex counties as opposed to upstate in New Castle County.
“The 2013 mosquito-disease transmission season is really only beginning, and it’s difficult to predict how intense the situation might become, with hotter than normal summers often making for worse disease outbreaks, such as what happened last year,” Meredith said.
As of July 23, the federal Centers for Disease Control (CDC) has reported 31 human West Nile cases and three deaths nationwide in 14 states, with Mississippi, South Dakota and Nevada having the most cases to date. 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 also occurred, with 17 confirmed human cases and 2 fatalities, plus 63 equine cases. Last year in 2012, there was a resurgence nationwide of WNV involving 5,674 human cases and 286 deaths, with nine WNV human cases in Delaware and one death, but no horse cases due to equine vaccinations.
Dr. Heather Hirst, State Veterinarian with the Delaware Department of Agriculture, said effective equine vaccines exist 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.”
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), or acute flaccid paralysis, and sometimes death. 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.
“Most people bitten by an infected mosquito won’t get sick,” said Dr. Karyl Rattay, Division of Public Health Director. “Others are not as lucky. The risk of severe disease, such as meningitis and encephalitis, increases with age resulting in the elderly being at higher risk for complications.”
“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.
"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. Use insect spray whenever outdoors."
To reduce mosquito-breeding, Meredith said people should drain or remove 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, downspout extenders, and unused swimming pools.
“The possibility of mosquito-borne disease transmissions now won’t subside until cooler autumn temperatures set in, usually in mid-October and sometimes even later,” Meredith added.
To help determine when and where control services are needed, Mosquito Control 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, www.cdc.gov/ncidod/dvbid/westnile/index.htm
Vol. 43, No. 298