As the transition into spring and summer is underway, please be aware that the Chester County Health Department (CCHD) will be continuing to monitor mosquito populations across Chester County for presence of West Nile Virus (WNV). CCHD utilizes a variety of sampling methods to monitor mosquito populations, including the use of traps designed to capture adult mosquitoes, as well as the collection of larval mosquito samples from standing or stagnant water sources. Additionally, CCHD personnel are available to respond to mosquito-related complaints submitted by residents.
In the attached document, you will find descriptions of mosquito trap surveillance and sampling methods as well as images of the traps themselves. We want to share this information with you in case there are concerns about these devices should you come across them in local areas such as parks.
If WNV is detected in collected mosquito samples, CCHD’s performs additional surveillance around the initial detection site to determine the extent of infection in the surrounding area. If other sites are yielding WNV-infected mosquitoes, we would begin population control efforts. CCHD uses Integrated Pest Management (IPM), which may include physical, biological, or chemical control methods. CCHD will consider alternatives to biological and chemical pesticides when practical to include local education and outreach, prevention of breeding sites, and reduction of breeding sites. We also perform larval sampling around the affected site and, when mosquito larvae are found, we perform treatments of the water source using a safe bacterial product containing Bacillus thuringiensis israeliensis (Bti) or Bacillus sphaericus (Bs), which are naturally occurring soil bacteria.
If sampling continues to detect high levels of WNV-infected mosquitoes after additional surveillance and control methods, the final option is to perform a truck-mounted treatment targeting adult mosquitoes. If a truck-mounted adult mosquito treatment is recommended for your area, CCHD will provide ample notification to you ahead of time to make you aware of any upcoming treatments. Additionally, CCHD personnel will be available to answer questions and provide information.