Determination of need for mosquito control in the Great Dismal Swamp National Wildlife Refuge

Rationale: In 1998 a confirmed EEE case in Portsmouth, Virginia proved to be fatal followed by another fatal case in Gloucester, Virginia in 2003. As a result of these cases, management of mosquitoes that vector WNV and EEE has possibly necessitated using insecticides in areas where they traditionally have not been used, including protected wildlife refuges such as the Great Dismal Swamp, located in southeastern Virginia and Northeastern North Carolina. Objective: To review and compile statistical data on cases of West Nile Virus and Eastern Equine Encephalitis supplied by the Chesapeake Mosquito Control Commission in order to assess the need for insecticide use in the Great Dismal Swamp National Wildlife Refuge. Methods: Data was gathered for the years 2003, 2004 and 2005 for the sentinel chicken, horse and mosquito populations in Chesapeake, Virginia. A risk assessment of the Great Dismal Swamp was performed and an action plan for implementing mosquito control in the Great Dismal Swamp developed. Results: Positive cases of EEE and WNV were found in 2003, 2004, and 2005 in the sentinel chicken, horse and mosquito populations with 54% found within a mile of the refuge. Conclusion: When a certain level of EEE and WNV disease activity is reached within the mosquito and animal population, there is an increased health risk to humans and thus additional response is needed. Determining the appropriate level and type of response requires use of the integrated pest management techniques including source reduction, surveillance, biological controls, public education, and often larviciding and adulticiding.