Contact: Joanna Wilson, DNREC Public Affairs, 302-739-9902
Public requested to report sick or dead wild birds to DNREC’s
Mosquito Control Section for 2013 West Nile virus monitoring
DOVER (June 4, 2013) – DNREC’s Division of Fish and Wildlife Mosquito Control Section is again asking the public’s help in monitoring West Nile virus in Delaware by reporting sick or dead wild birds of certain species that may have contracted the virus. West Nile virus (WNV) is a mosquito-borne disease that rates of considerable concern to the health of humans and unvaccinated horses.
Beginning now, the Mosquito Control Section requests that the public report sick or dead birds of the following species only: crows, blue jays, cardinals, robins, and hawks or owls, plus clusters of three or more sick or dead wild birds of any species. Bird specimens should have been dead for less than 24 hours and not appear to have died or been killed by other obvious causes. The collecting and testing of virus-suspect wild birds may continue through the end of September, said Dr. William Meredith, Delaware Mosquito Control administrator.
After initial processing by the Delaware Department of Agriculture’s Poultry & Animal Health Lab, bird specimens collected by Mosquito Control are submitted to the Delaware Public Health (DPH) Laboratory for virus testing. From early July through mid- to late October, Mosquito Control also will operate its statewide network of 23 sentinel chicken stations, which “keep watch” for WNV and eastern equine encephalitis (EEE), another mosquito-borne viral disease that affects horses and humans. The DPH lab tests the sentinel chickens’ blood for these viruses to help indicate where WNV has been transmitted by mosquitoes from wild bird hosts to other animals, possibly leading to an increased risk of exposure for humans or horses.
As with other parts of the country, West Nile virus had a resurgence in Delaware last summer, with nine human cases and one fatality during 2012. This disease is transmitted to humans primarily by the common house mosquito, and possibly by Asian tiger mosquitoes. WNV first appeared in Delaware in 2001, with its peak year being 2003, with 17 reported human cases and two human fatalities, as well as 60 WNV-stricken horses. From 2004 through 2011, WNV numbers were lower in Delaware. In 2004 and 2006, no cases of WNV were reported in humans or horses; in 2005 two human cases were reported, with no horse cases; and in both 2007 and 2008, only one human case was reported and no horse cases. More recently, only one human case and one equine case of WNV were reported in 2011.
“Considering the prevalence and extent of prime mosquito production habitats in Delaware, combined with our high human population density, this can present quite a challenge, but our effective approach to controlling mosquitoes has helped reduce the frequency of West Nile virus transmission,” Dr. Meredith said.
For 2012, the Centers for Disease Control and Prevention’s nationwide figures show 5,674 reported human cases of West Nile virus resulting in 286 deaths, with the most cases occurring in descending order in Texas, California, Louisiana, Illinois, Mississippi, South Dakota, and Michigan. Regionally, 107 WNV human cases were reported in New York during 2012, 60 occurred in Pennsylvania, 48 in New Jersey, 47 in Maryland, 30 in Virginia, 21 in Connecticut, and 10 in the District of Columbia.
“Over the past decade, WNV might have reduced populations in Delaware of some virus-susceptible birds such as crows, while surviving members of crows and other bird species may have become more resistant to the virus’ effects, perhaps as a type of flock immunity response,” Dr. Meredith said. “This could account for a decrease in WNV-infected wild bird findings during recent years. Additionally, with WNV not quite as alarming to the public as when it first surfaced, the reporting of sick or dead wild birds may have also diminished in importance.”
Due to complicated environmental reasons, wild birds are probably better indicators of WNV early in the season from May through July than Mosquito Control’s sentinel chickens, which become better indicators later, from August through October. Weather conditions could also impact this year’s West Nile numbers, whether found in wild birds, sentinel chickens or mosquitoes themselves, as epidemiologic evidence suggests that outbreaks might be more severe during abnormally hot years, with 2012 a good example. Within any given year regardless of total numbers of cases, the gravest period of concern for disease transmission is in late summer and early fall, Dr. Meredith said.
The Mosquito Control Section will also continue to document all phone reports of West Nile bird species of interest, but will be selective in collecting and analyzing reported birds. As the season progresses, Mosquito Control will stop analyzing specimens from any areas where a number of virus-positive birds have been found, although it will continue to solicit public reporting of virus-suspect birds for these areas.
Dr. Meredith also noted that there is no cause for alarm that uncollected specimens might transmit WNV to humans, or to pets that could consume a sick or dead bird. Dead birds can be left to decompose in place, or they can be buried, or bagged and disposed of in the garbage. He advises, when disposing of any dead bird to avoid direct skin contact by wearing gloves and/or by using a shovel.
Sick or dead birds can be reported to the Mosquito Control Section between 8 a.m. and 4 p.m., Monday through Friday, by calling Mosquito Control’s field offices:
- New Castle County and northern Kent County from Dover north, call Mosquito Control’s Glasgow office at 302-836-2555
- Remainder of southern Kent County and all of Sussex County, call Mosquito Control’s Milford office at 302-422-1512
These numbers may also be used to report intolerable numbers of biting mosquitoes to help the Mosquito Control Section determine when and where to provide control services. For more information on Delaware’s Mosquito Control program, please call the main office at 302-739-9917, or visit http://www.fw.delaware.gov/Services/Pages/MosquitoSection.aspx.
Calls made to the field offices after business hours or during weekends or holidays can be recorded. Callers should give their name, phone number, address, and a brief message. However, the public should be aware that some calls left more than 24 hours before Mosquito Control can review them – typically involving times between Friday evening and Sunday morning when staff might not be present – can unfortunately result in birds becoming too deteriorated for virus testing.
For more information about West Nile virus in humans, please contact the Delaware Division of Public Health at 302-744-1033 or 888-295-5156. For more information about West Nile virus in horses, eastern equine encephalitis or vaccines, please contact the State Veterinarian at the Delaware Department of Agriculture at 800-282-8685 (Delaware only) or 302-698-4500.
Vol. 43, No. 225