Oct. 14, 2008
Vol. 38, No. 469

For more information, contact William Meredith, Division of Fish and Wildlife Mosquito Control Section, 302-739-9917 or Joanna Wilson, Public Affairs 302-739-9902.

Eastern Equine Encephalitis Found in Delaware for First Time in 2008

DNREC’s Mosquito Control Section announces that Eastern Equine Encephalitis (EEE) has been found in Delaware for the first time in 2008. The virus was found in three sentinel chickens sampled at three different monitoring stations, which are part of a statewide network of 24 sentinel chicken stations operated by Mosquito Control to help monitor for both EEE and West Nile virus, the primary mosquito-borne human health threats in Delaware.    

On Oct. 9, the Division of Public Health Laboratory reported the EEE-positive results for blood samples that Mosquito Control drew from the three chickens on Oct. 6. The chickens were from from Kent County’s Kenton and Logan Lane stations and a New Castle County station in New Castle.

“In reaction to these EEE-positive findings, and in addition to Mosquito Control’s normal mosquito population monitoring efforts, the Section will increase its monitoring in the affected areas and take mosquito control actions as warranted,” said Dr. William Meredith, Delaware’s Mosquito Control administrator.

The Public Health Laboratory also reported on Oct. 9 the finding of West Nile virus in a sentinel chicken sampled by Mosquito Control on Oct. 6 from another New Castle County station at Cherry Island. This latest finding brings this year’s total number of West Nile virus-positive sentinel chickens in Delaware to 17. The first finding was reported Aug. 18, with West Nile subsequently occurring in all three counties. 

“In comparison to the occurrence of West Nile virus in Delaware over the past seven years, EEE has long been in Delaware and fortunately is much rarer,” Meredith said. “However, EEE can be much more health-threatening to the few who contract the disease, having a significantly higher fatality rate than West Nile.”

The transmission of EEE to humans is more often linked to saltmarsh mosquitoes or closely-related freshwater wetland species, versus container-breeding mosquitoes found in populated areas more closely associated with West Nile virus transmissions, Meredith added. In addition to mimicking West Nile as a concern for the elderly or people with weakened immune systems, EEE can also be very serious for infants and children, and often problematic even to healthy adults. 

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, creating a period when disease transmissions to humans or horses become of greatest concern.

Depending upon how warm or mild early autumn might be during any given year, mosquito populations can remain relatively high and active into late October or even early November, and if so then the concern for mosquito-borne disease transmissions also remains elevated, Meredith said. These mosquito problems will not fully subside until after the first night of a hard-killing freeze, when air temperature dips below 28 degrees for four or more hours.   

“Delawareans still need to be aware about possible mosquito-borne problems for at least the next few weeks,” Meredith said. “While the EEE findings are not cause for alarm, they should prompt concern, and people need to take additional personal protection measures to reduce or avoid mosquito bites.” 

To reduce the chance of infection, Mosquito Control and the Division of Public Health advise residents to take these common-sense precautions against mosquito bites:

• Following all label instructions, apply insect repellent containing less than 30 percent DEET for adults, less than 10 percent DEET for children; picaridin and oil of lemon eucalyptus are now other mosquito repellents recognized as effective by the EPA;
   
• Wear long-sleeved shirts and pants outdoors in mosquito-infested areas;

• Avoid peak mosquito activity during dusk, evening or early morning; and

• Drain or remove items that collect unneeded water that sits for more than four consecutive days, serving as mosquito-breeding habitat, such as upright wheelbarrows, buckets, rain barrels, old tires, depressions in tarps covering boats, discarded cans and barrels, flower pots, blocked rain gutters and unused swimming pools. Water in birdbaths and children’s wading pools should be changed frequently.

The Division of Public Health reports that humans infected with West Nile virus typically have only mild symptoms similar to a mild flu, if they show any signs at all. Rarely do humans infected with the disease experience sudden onset of severe headache, high fever, stiff neck, confusion and muscle weakness. Early symptoms of contracting EEE can be similar, but often become more pronounced and debilitating. Individuals with these symptoms should see their physician immediately. 

The Department of Agriculture’s State Veterinarian urges horse owners to contact their veterinarian if they suspect a horse has EEE or West Nile virus. Symptoms in horses include listlessness, muscle spasms in the head and neck, tremors or staggering, and hind-limb weakness. Both EEE and West Nile equine vaccines are available through your veterinarian.

Mosquito Control uses trucks or aircraft to apply as warranted insecticides registered by the U.S. Environmental Protection Agency to reduce larval and adult mosquitoes. In accordance with EPA determinations, these products pose no unreasonable risks to human health, wildlife or the environment.  For the avoidance or control of EEE and West Nile, the Section will continue water management practices and insecticide use to control larval mosquitoes in their breeding habitats, and also to apply insecticides to control adult mosquitoes that couldn’t be controlled during their immature aquatic stages. 

DNREC also encourages individuals who find sick or dead crows, blue jays, cardinals, robins, or hawks or owls to call the Mosquito Control Section, Monday through Friday from 8 a.m. to 4 p.m., at the phone numbers below. Residents should wear gloves and avoid direct skin contact if they handle sick or dead birds.

New Castle County and northwestern Kent County: 302-836-2555

Remainder of Kent County and all of Sussex County: 302-422-1512

These numbers should also be used to report mosquito problems. 

For questions about the state’s Mosquito Control program or mosquito biology, call DNREC at 302-739-9917.

For human health questions about EEE or West Nile virus, call the Delaware Division of Public Health at 888-295-5156 or 302-744-4541.

For questions about EEE or West Nile in animals, call the Delaware Department of Agriculture at 800-282-8685 (Delaware only) or 302-698-4500, and ask for Poultry-Animal Health.