ANNAPOLIS, MD – The Maryland Department of Agriculture has announced the first detection of a West Nile virus mosquito pool in Maryland in 2018. On July 23, the Maryland Department of Health confirmed the presence of West Nile virus in mosquitoes collected by department personnel in the Riverdale Park area (Prince George’s County) on July 11. The department will use Ultra-Low Volume (ULV) truck-based spraying to control adult mosquitoes within a ¾ mile radius of the positive sample; this includes parts of Riverdale Park, Hyattsville, Edmonston, and Rogers Heights. Most of the area has already been treated during routine mosquito control sprays. The remaining area will be treated Thursday evening, weather permitting. The department’s mosquito control personnel continue to work aggressively to reduce mosquito populations in these communities and across the state.

“We know that West Nile virus may be present throughout Maryland. It typically appears at this time in the summer, so we are not surprised with this positive finding,” said Secretary of Agriculture Joe Bartenfelder. “The confirmation of virus-positive mosquitoes serves as a reminder to all residents to continue protecting themselves against mosquito bites and to conduct backyard mosquito control activities in addition to the department’s routine surveillance and spray activities.”

The department’s Mosquito Control Office, in cooperation with the Department of Health, has been conducting surveillance activities throughout the state to collect and test mosquitoes for West Nile virus, Eastern Equine Encephalitis and several other mosquito-borne diseases. These diseases are endemic in Maryland and are transmitted through the bite of a mosquito. Approximately 20 percent of people infected with West Nile virus will develop West Nile fever, which is typically characterized by fever, headache, and body aches which can last for just a few days or as long as several weeks. Less than one percent of people bitten by a mosquito carrying West Nile virus will develop a more severe form of the disease. People most at risk for developing severe disease are those over 60 and those with already compromised immune systems.

While not all mosquitoes carry these diseases, the Maryland Department of Agriculture suggests that residents take precautions to minimize their exposure to mosquito bites. These measures include:

  • Wear long, loose fitting, light colored clothing
  • Wear insect repellents according to product labels
  • Avoid mosquito infested areas during prime periods of activity (between dusk and dawn)
  • Install, inspect, and repair window and door screens in homes and stables
  • Regularly clean bird baths and bowls for pet food and water
  • Remove or empty all water-holding containers

Currently there is no WNV vaccine for humans. There are, however, effective vaccines for horses, ostriches and emus – also known as ratites. Owners are encouraged to get their animals vaccinated and boostered in a timely manner in consultation with their veterinarian.

Dog owners are also urged to have their pets checked for heartworms, the most common disease transmitted by mosquitoes in Maryland. Dogs in all Maryland jurisdictions should be placed on a heartworm preventive program. Pet owners should consult with their veterinarians.

For more information about mosquito-borne diseases, contact your local health department. The following websites are available to provide additional information: