DOVER — An increase in mosquito-transmitted West Nile virus is occurring in many areas in Delaware, as indicated in sentinel chickens used by the Department of Natural Resources and Environmental Control to monitor for the disease.
Twenty sentinel chicken stations are sampled weekly throughout the state each summer and fall to help track WNV and eastern equine encephalitis, the primary mosquito-transmitted human health threats in Delaware. The virus occurrences in these chickens are unrelated to the poultry industry.
Forty sentinel chickens have tested positive for WNV to date, with over half of these findings, 25, in the last few weeks. WNV has been detected in 10 of the stations — with 32 chickens from six stations in New Castle County, four chickens from two stations in Kent County and four chickens from two stations in Sussex County.
This higher initial gradient of WNV detection upstate is followed in most years with increased WNV occurrences Downstate in midfall. EEE has not been found this year in the sentinel chickens.
There has been one WNV case in a human in 2021, reported Sept. 3 by the Delaware Division of Public Health. No human EEE cases have been reported this year.
Staff from DNREC’s Division of Fish & Wildlife humanely care for these sentinel chickens. Blood samples collected by the DNREC Mosquito Control Section are tested for evidence of WNV and EEE by the Delaware Public Health Laboratory.
This is the peak time of year for mosquito-transmitted diseases, continuing until the onset of colder weather. While these recent WNV findings are not cause for alarm, residents and visitors are urged to be vigilant over the coming weeks by wearing long-sleeved shirts and long pants, applying insect repellent and avoiding mosquito-infested areas and times of peak mosquito activity around dusk, dawn and at night.
More measures, like draining outdoor items that collect water, can be taken by property owners.
Both WNV and EEE can adversely affect people and horses, but there are no human vaccines for either. About 80% of people infected with WNV show no symptoms, while the remainder develop mild illness. Only about 1 in 150 people might develop severe infection, indicated by high fever, disorientation, tremors or convulsions, encephalitis or meningitis, all possibly leading to hospitalization and, very rarely, death.
EEE can be a more severe disease than WNV — with a human fatality rate greater than 30% — though EEE is much rarer than WNV.
The Mosquito Control Section has increased surveillance efforts in the vicinity of virus-positive findings and initiated targeted control actions, based on species and the numbers encountered.
For more information, call the Mosquito Control Section’s Dover office at 739-9917. To report suspected cases of human WNV, call the Office of Infectious Disease Epidemiology at 888-295-5156.