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Skip Navigation LinksDNREC : News : Eastern Equine Encephalitis reported in Delaware through DNREC sentinel chickens for first time since 2008

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Contact: Joanna Wilson, DNREC Public Affairs, 302-739-9902, or Jill Fredel, DHSS, 302-255-9047.

Eastern Equine Encephalitis reported in Delaware
through DNREC sentinel chickens for first time since 2008
Evidence of West Nile virus increases

DOVER (Aug. 16, 2013) – For the first time since 2008 Delaware has recorded a finding of Eastern Equine Encephalitis (EEE), after a sentinel chicken tested positive for the virus. The Delaware Public Health Laboratory confirmed the presence of the virus on Aug. 13. This finding occurred within a statewide network of 24 sentinel chicken stations administered by DNREC’s Division of Fish and Wildlife Mosquito Control Section to help monitor for both EEE and West Nile virus (WNV), the primary mosquito-borne human health threats in Delaware.

The chicken found to have the encephalitis virus was sampled at a monitoring station near Frankford in Sussex County. “In reaction to this EEE-positive finding, and in addition to normal mosquito population monitoring efforts, Mosquito Control increased its monitoring in the Great Cypress Swamp area. On Aug. 14, we ground-fogged the towns of Gumboro and Frankford, the Route 54 corridor, and portions of Selbyville. As we continue monitoring the area, we will take additional mosquito control actions as needed,” said DNREC Mosquito Control Administrator Dr. William Meredith. “The public also should be aware that recent virus activity indicates that the potential for transmitting and contracting mosquito-borne diseases has increased statewide.”

EEE was last detected in Delaware in October 2008, in three birds from the sentinel chicken network from near New Castle, Kenton and Little Creek. The last reports for EEE-positive chickens from Great Cypress Swamp were for two birds in early autumn 2005. The last recorded case of EEE in humans in Delaware was in 1979.

The Public Health Laboratory also reported on Aug. 12 the finding of West Nile virus in three more sentinel chickens sampled by Mosquito Control, bringing the total to six WNV-positive birds for 2013. The three most recent WNV findings come from stations near Stanton, Middletown and Blackbird, joining previously-reported WNV-positive chickens near Leipsic and Georgetown on July 22. In addition, Mosquito Control received the first reports of WNV in wild birds, beginning with a blue jay collected near Lewes on July 25, followed by another blue jay near Dover, a crow near Millsboro and, most recently, a hawk near Camden on Aug. 8. 

While the EEE and WNV findings are not cause for alarm, Delawareans should take precautions to reduce or avoid mosquito bites for at least the next two months or until the first hard frost, when mosquito populations will subside, Dr. Meredith said. Mosquito Control and the Delaware Division of Public Health advise residents to avoid mosquito-infested areas or times of peak mosquito activity around dusk, dawn or throughout the evening; to wear long-sleeved shirts and long pants outdoors; and to apply insect repellent containing 30 percent or less DEET for adults and 10 percent or less DEET for children. Picaridin and oil of lemon eucalyptus are now other mosquito repellents recognized as effective by the EPA.

The Division of Public Health reports that humans infected with WNV typically have only 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 develop severe neurological disease resulting in meningitis or encephalitis (inflammation of the brain), or acute flaccid paralysis, and sometimes death. Symptoms in those cases may include sudden onset of severe headache, high fever, stiff neck, confusion and muscle weakness. Individuals with these symptoms should see their physician immediately.

Early symptoms of EEE can be similar to WNV, but often become more debilitating. EEE is much rarer than WNV but can be more health-threatening, and with a higher fatality rate than West Nile. Transmission of EEE to humans is often linked to saltmarsh mosquitoes or closely-related freshwater wetland species, Meredith said, versus the container-breeding mosquitoes found in populated areas associated with WNV transmissions. Like WNV, EEE can be very serious for the elderly, people with weakened immune systems, infants and children. There are no approved WNV or EEE vaccines for humans.

Effective EEE and West Nile vaccines are available for horses through veterinarians, according to the Delaware Department of Agriculture’s State Veterinarian’s Office. The State Veterinarian urges horse owners to contact their veterinarian immediately if they suspect a horse may be showing clinical signs of EEE or WNV. Symptoms of EEE in horses include fever (102.5-104.5°F), loss of appetite, head pressing, depression or personality change, wobbling or staggering, weakness, blindness, convulsions, muscle tremors in the head and neck, and hind-limb weakness. These symptoms are also consistent with WNV, though a fever may not be present with WNV.

Concerns about transmission of EEE to humans are highest in locations where wet woodlands are near tidal wetlands. Such areas harbor mosquito species that can serve as vectors for EEE, after first contracting the virus from infected wild birds.     

Mosquito-borne pathogens such as EEE or West Nile typically build in the environment throughout the summer, both in wild bird and mosquito populations, reaching peak levels in late summer and early autumn, when disease transmissions to humans or horses become the greatest concern. During years with a mild autumn, mosquito populations can remain relatively high and active into late October or early November, with concern for mosquito-borne disease transmission also remaining elevated until the first night of a hard freeze, when air temperature dips below 28 degrees for four or more hours.

Above average rainfall amounts this summer have contributed to higher mosquito populations than normal this year, possibly increasing the potential for mosquito-borne disease transmissions, Meredith said, and rainfall amounts for the rest of this summer and into the fall will continue to impact mosquito populations.

To reduce mosquito-breeding, Meredith said residents 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. Water in birdbaths and children's wading pools should be changed frequently.

DNREC also encourages individuals who find sick or dead crows, blue jays, cardinals, robins, or hawks or owls – species that are susceptible to WNV – to report their findings by calling the numbers below. Residents should wear gloves and avoid direct skin contact if they handle sick or dead birds.

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 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 information about:

  • Mosquito biology and control – Contact the Mosquito Control’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. 43, No. 316

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