Evidence of EEE Detected in DNREC’s Sentinel Chickens

Eastern Equine Encephalitis (EEE), a mosquito-transmitted disease, has been detected in Delaware the first time for 2022 in a sentinel chicken, the Delaware Department of Natural Resources and Environmental Control announced today. Mosquito-transmitted virus detections in DNREC’s sentinel chickens are unrelated to Delaware’s poultry industry.

The EEE finding in northern New Castle County was from a sentinel chicken station sampled by the DNREC Division of Fish and Wildlife Mosquito Control section and confirmed by the Delaware Public Health Laboratory Aug. 9. While there have been no reported EEE cases in humans this year in the state, Delawareans are reminded that the possibility of contracting mosquito-transmitted diseases, including EEE and West Nile Virus (WNV), will continue until colder autumn temperatures in late-October or later.

The first EEE-positive sentinel chicken for this year adds to five WNV-positive sentinel chickens found earlier at three other sentinel chicken arbovirus monitoring stations in New Castle and Kent counties – with the first WNV finding occurring in early July. No EEE or WNV human cases have been reported to date in 2022 by the Delaware Public Health Laboratory, nor have any EEE or WNV equine cases been reported by the Delaware Department of Agriculture.

Blood samples are collected by the Mosquito Control section each week from early July into October from the state’s outdoor-caged sentinel chickens that are humanely housed and handled at 20 monitoring stations statewide. The blood samples are tested for EEE and WNV antibodies by the Delaware Public Health Laboratory. Sentinel chickens bitten by mosquitoes carrying EEE or WNV develop antibodies to these diseases but are otherwise unaffected. Mosquitoes can transmit both WNV and EEE to humans and horses.

The public is reminded to take common-sense precautions to avoid mosquito bites, including wearing long-sleeved shirts and long pants when outdoors in mosquito-prone areas, applying insect repellent containing 10 to 30% diethyltoluamide (DEET) in accordance with label instructions and avoiding mosquito-infested areas and at times of peak mosquito activity around dusk, dawn and at night.

Spraying to reduce mosquito populations in areas where EEE or WNV is detected may be initiated by DNREC’s Mosquito Control section as warranted, based on factors to include mosquito population levels and mosquito species present in affected areas. To reduce mosquito-breeding habitat and chances of disease transmission, residents should drain or remove outdoor items that collect water, such as discarded buckets or containers, uncovered trashcans, stagnant birdbaths, unprotected rain barrels or cisterns, old tires, upright wheelbarrows, flowerpot liners, depressions in boat tarps, clogged rain gutters, corrugated downspout extenders and unused swimming pools.

While EEE is rarer than WNV, both EEE and WNV can adversely affect people and horses. Most people who become infected with EEE virus and WNV show either no or mild symptoms. Early symptoms in people contracting EEE or WNV can be similar, but EEE often becomes more pronounced and debilitating, manifested by meningitis or encephalitis typically resulting in hospitalizations. EEE has a higher human mortality rate of approximately 30%, with infants, children and the elderly most vulnerable, according to the U.S. Centers for Disease Control and Prevention. Symptoms in people infected with EEE usually start from four to 10 days after being bitten by a mosquito infected with EEE. Early EEE symptoms can include headache, high fever, stiff neck, tremors or muscle weakness, with more severe cases progressing to stupor, disorientation, coma, convulsions, paralysis and possibly death. Most people infected with WNV do not develop symptoms, but about 20% can develop a mild illness, including fever, body and muscle aches, headache, nausea, vomiting, and rash symptoms. A small number of people infected with WNV can develop serious illness involving neurological problems, paralysis and possibly death. There are no human vaccines for EEE or WNV. Anyone developing the symptoms described above should see their healthcare provider.

Horse owners should contact their veterinarian immediately if they suspect their horse may be showing signs of WNV or EEE. 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 or hind-limb weakness. These signs are also consistent with WNV, although a fever may or may not be present with WNV.

Additional information about mosquitoes and mosquito-transmitted diseases is available from the following resources:

For mosquito biology/ecology and control, contact the Mosquito Control section office in Dover at 302-739-9917.

For requests for mosquito relief in upstate areas from Dover north, contact Mosquito Control’s Glasgow field office at 302-836-2555.

For requests for mosquito relief in downstate areas south of Dover, contact Mosquito Control’s Milford field office at 302-422-1512.

For animal health questions, contact the Delaware Department of Agriculture’s Poultry and Animal Health Section at 302-698-4500.

To report suspected cases of human EEE or WNV, call the Division of Public Health Office of Infectious Disease Epidemiology toll-free at 888-295-5156.

For more information on Eastern Equine Encephalitis or West Nile Virus, visit www.cdc.gov/ncidod/dvbid/westnile/index.htm.