Tests turned up West Nile virus in chickens in the Great Cypress Swamp in the south-central part of Sussex County this week.
The first 2004 finding of West Nile virus in Delaware was found July 26 in blood samples of sentinel chickens monitored for mosquito-borne diseases. The finding is part of a statewide surveillance program conducted by the Mosquito Control Section of the Department of Natural Resources and Environmental Control.
The test results, provided by the Delaware Public Health Laboratory came from two sentinel chickens sampled on July 19 from a single cage station located in the Great Cypress Swamp. This area has historically been a “hot spot” for eastern equine encephalitis, another mosquito-borne disease that affects humans.
This is the first time since West Nile virus was found in Delaware in 2000 that the first finding of the year is in sentinel chickens rather than sick or dead wild birds such as crows and blue jays. This year, no positive human or horse West Nile cases have yet been found in Delaware, and no wild birds have tested positive for the virus.
The appearance of West Nile virus this year first in sentinel chickens rather than in wild birds is a bit surprising, according to Dr. William Meredith, mosquito control section administrator.
“This may reflect the public’s finding and reporting fewer virus-suspect birds than in past years,” Meredith said. “We’ve experienced a significant decrease in reporting of crows or blue jays that are more susceptible to the disease and perhaps could have died off in large numbers over the past few years, with other species of birds remaining more resistant to the virus.
"However, other species of more resistant birds can still be troublesome hosts for infecting mosquitoes that feed upon them and in turn create virus-carrying mosquitoes that can then bite humans or horses,” Meredith said.
Nationwide, according to the Centers for Disease Control and Prevention, as of July 20 this year, there have been 182 human cases of West Nile virus, with the bulk of these cases in Arizona, California and Colorado. During 2004, West Nile has been detected in wild birds from 39 states, indicating widespread occurrence again.
On a regional basis, one human case of West Nile has now been reported from New York and one human case from Pennsylvania was reported in the news Sunday. Horse cases have been found in Virginia, and the virus has been detected in mosquito collections from Pennsylvania, New Jersey and Virginia.
The positive results in the sentinel chickens serve as a reminder for Delawareans to continue their vigilance and take precautions to lower their risk for contracting this disease. Preventive measures include avoiding places where mosquitoes are abundant or actively biting whenever possible, wearing long-sleeve shirts and pants, and appropriately using effective insect repellents. Wear insect repellent containing less than 50 percent DEET for adults, less than 30 percent DEET for children. Follow directions on the label.
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. Individuals with these symptoms should see their physician immediately.
Dr. Wesley Towers, state veterinarian urges horse owners to contact their veterinarian if they suspect a horse has West Nile virus. Symptoms in -horses include listlessness, muscle spasms in the head and neck, and hind-limb weakness. A West Nile equine vaccine is now available through
To help decrease local mosquito production, any sources of stagnant water around a residence or business that remain for more than four consecutive days should be eliminated. The Mosquito Control Section will continue to monitor mosquito populations around the state, track virus activity and take appropriate control actions.
In response to the Great Cypress Swamp finding, the section will be setting some additional mosquito sampling traps in or near Gumboro, Dagsboro, Selbyville, and Frankford.
DNREC encourages individuals who find dead crows, blue jays, 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 provided below. These numbers should also be used to report mosquito problems. Residents who may need to handle any dead birds should wear gloves and avoid direct skin contact.
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