DNREC Mosquito Control to discontinue wild bird testing for West Nile

by Dave on May 26, 2010

The Delaware Mosquito Control Section will make some changes this year to update its statewide monitoring program for West Nile virus, a mosquito-borne disease of concern to both humans and horses. Plans call for discontinuing the section’s annual testing program for wild birds as indicators of the presence of West Nile, while continuing to operate its statewide network of sentinel chicken stations used to detect West Nile and eastern equine encephalitis (EEE). The section will also add new testing measures as a trial project.

Since West Nile virus first appeared in Delaware in 2001, the section has worked with the Delaware Public Health Laboratory, using statewide findings of West Nile in wild birds to help monitor when and where the disease appears in Delaware each year and focus control actions as warranted. The program’s peak occurred from 2002 to 2004, when hundreds of wild bird specimens were reported, collected and tested. More recently, numbers have dwindled to only a few dozen birds per year.

A number of possible reasons may have contributed to this decline, including the success of aggressive mosquito control measures and reduced public participation in the program. Scientists believe that many wild bird populations also have now developed a type of “flock immunity” to West Nile, making them less susceptible to the disease, though they can still carry and transmit it to mosquitoes which can then infect humans and horses.

“The bottom line is that we feel the reporting, collection and testing of wild birds for West Nile virus is no longer a good detection method to assist with mosquito control operations in Delaware, a perspective shared by many other areas around the country,” said Mosquito Control Administrator William Meredith. Instead of calling to report sick or dead birds, citizens should now leave them alone or pick them up for disposal using a shovel or other implement if available and wearing gloves, especially if handling dead birds directly, Meredith added.

Funding for the wild bird testing program, which is primarily from federal grants, will be shifted to a trial project to enhance an existing statewide monitoring network of 36 adult mosquito light traps, which is used to monitor mosquito populations, target control actions and determine control effectiveness. The section will work with the DPH lab this summer to implement testing of samples from the traps for West Nile.

In addition, Mosquito Control’s statewide network of 23 sentinel chicken stations will operate from early July until early to mid-October instead of beginning in early June. “This timeframe gives us some cost savings while still allowing us to monitor the peak period for mosquito-borne virus occurrence from July into October,” Meredith said. Monitoring with sentinel chickens has proven to be an effective indicator of mosquito-borne viruses in Delaware since 1982, he said.

“West Nile virus might no longer be as apparent in wild bird populations, but it certainly hasn’t gone away,” Meredith continued, noting that residents should continue to follow precautions to minimize mosquito contact, such as using repellent and emptying standing water from containers such as flower pots, old tires and trash cans to reduce breeding areas.

Delawareans are encouraged to report mosquito control needs or concerns including intolerable infestations. Residents of New Castle County and northern Kent County including Dover, Little Creek, Kitts Hummock, Hartly, Marydel, Sandtown, Magnolia and Camden-Wyoming, can call the Glasgow Office at 302-836-2555. Residents of Sussex County and southern Kent County including Bowers Beach, Woodside, Viola, Frederica, Felton, Milford and Harrington can call the Milford Office at 302-422-1512.

Advance public notice of when and where spraying will occur this year will be given daily via radio announcements, by calling 800-338-8181 toll-free, or by visiting www.fw.delaware.gov/services/MosquitoSection.htm. Interested parties may also subscribe to receive email notices by visiting the DNREC homepage – click on “Email List Subscription” under Services and follow directions to sign up for mosquito control spray announcements.

For more information about Delaware’s Mosquito Control program, call 302-739-9917.

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