Public asked to report sick or dead wild birds to Delaware Mosquito Control

The public is asked to help monitor West Nile virus in Delaware by reporting discovery of sick or dead wild birds that may have contracted the virus. West Nile virus is a mosquito-borne disease of considerable concern to human health and to owners of unvaccinated horses.

"We are interested in when and where West Nile virus might again appear in Delaware this year, and in monitoring the timing and locations of its possible spread throughout the state," said Dr. William Meredith, Mosquito Control Section administrator in the Department of Natural Resources and Environmental Control's Division of Fish & Wildlife.  "Our sampling strategy this year is to collect and test a sample of wild birds found throughout the state into late September."

As in past years, the Mosquito Control Section requests that the public report sick or dead birds of the following species only: crows, blue jays, cardinals, robins, hawks or owls, plus clusters of five 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 by other obvious causes." The Mosquito Control Section also notes that uncollected wild bird specimens are very unlikely to transmit WNV to humans, or to pets that come in contact with a sick or dead bird.

Birds collected by DNREC are processed by the Delaware Department of Agriculture's Poultry & Animal Health Lab, and then submitted to the Division of Public Health Laboratory for virus testing. From July through mid- to late-October, DNREC's Mosquito Control Section also operates a statewide network of about 20 sentinel chicken stations placed in prime mosquito areas, which "keep watch" for WNV and eastern equine encephalitis, another mosquito-borne viral disease that affects horses and humans. The DPH lab tests blood samples from the sentinel chickens for both viruses to help indicate where WNV or EEE has been transmitted by mosquitoes from wild bird hosts to other animals, possibly leading to an increased risk of exposure for humans or horses.

"The prevalence of prime mosquito production habitats in Delaware, combined with our high human population density, presents quite a challenge, but our approach to controlling mosquitoes has been effective in reducing the frequency of West Nile virus transmission and helping to prevent large outbreaks," Meredith said.

The period of greatest concern for disease transmission is in late summer and early fall, he said - noting that two other mosquito-borne diseases of concern late in South and Central America and the Caribbean, and now in the southern United States and possibly Delaware, are the chikungunya and Zika viruses. However, neither of these two diseases involves wild birds as host reservoirs for the viruses, but rather are diseases transmitted by mosquitoes from person-to-person with no avian involvement.

WNV is transmitted to humans primarily by the common house mosquito, and possibly by Asian tiger mosquitoes. The disease first appeared in Delaware in 2001, with a peak year in 2003, which saw 17 reported human cases and two fatalities, as well as 60 WNV-stricken horses. Delaware had no human cases of West Nile virus in 2016, a year for which the Centers for Disease Control's (CDC) nationwide figures were 2,038 reported human cases of WNV resulting in 94 deaths. Regionally last year, 19 WNV human cases were reported in New York with one death, 16 cases in Pennsylvania with two deaths, 11 cases in New Jersey with one death, and eight cases in Virginia, six in Maryland, and one in the District of Columbia, with no deaths reported from the last three.

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 office in Sussex County, Milford office: 302-422-1512.