PREPARED BY: Environmental Health Department
DATE: 2025-05-15
SUBJECT: 2025 Vector-borne Surveillance Program
BACKGROUND/PURPOSE
The Windsor-Essex County Health Unit (WECHU) delivers a vector-borne surveillance program to monitor West Nile Virus (WNV), Eastern Equine Encephalitis (EEE), Zika Virus and Lyme disease activity throughout Windsor and Essex County (WEC). The program provides the community with an early warning system for disease transmission through ticks and mosquitoes known to cause vector-borne diseases. This program is made up of the following components: mosquito larval surveillance and larviciding, adult mosquito trapping, human case surveillance, public education, and active tick surveillance. WNV and Lyme disease are reportable diseases of public health significance in Ontario and the WECHU follows up on all reported cases of WNV and Lyme disease in our region. The tasks of mosquito larval surveillance and control, along with mosquito identification and viral testing, are performed by contracted agencies on behalf of the WECHU.
DISCUSSION
Active Tick Surveillance
Lyme disease is a vector-borne disease caused by the bacterium Borrelia burgdorferi. It is transmitted to humans through the bite of infected black-legged ticks. The WECHU's role is to measure and evaluate the risk of this tick-borne disease in our area. All of Windsor and Essex County (WEC) is considered a blacklegged tick and Lyme disease risk area based on the updated Public Health Ontario blacklegged tick risk area map.
Active surveillance is used to assess the local distribution and incidence of black-legged ticks in WEC. It involves the dragging of a white cloth through grassy areas whereby ticks attach themselves to the fabric and can be easily spotted and identified. Any black-legged ticks identified are sent to an accredited laboratory for testing of Lyme disease. In 2024, 17 Lyme disease cases were reported to the WECHU which was the highest in comparison to previous years. The May 2025 Resolution Report – Lyme Disease Prevention Strategies outlines the need for ongoing proactive education and management of tick habitats to reduce tick bites and transmission of Lyme disease.
In 2025, tick dragging will be performed in the spring and in the fall at four locations where active surveillance has not been previously conducted. Previous locations such as Ojibway Park are endemic for black legged ticks and therefore new locations were selected. Tick dragging sites were chosen based on the 2024 data where the positive human cases may have acquired the ticks, as well as locations frequented by the public that support tick habitats.
Tick dragging will be conducted at the following four new sites in May and September:
- Devonwood Conservation Area (1830 Division Rd, Windsor, ON, N8W 1Z6)
- Rowsom’s Tilbury West Conservation Area (15172 S Middle Rd, Comber, ON, N0P 1J0)
- Rotary Club of Harrow Community Entrance (Chrysler Greenway, Harrow, ON, N0R 1G0)
- Malden Park & Woodland Trails (4300 Matchett Rd, Windsor, ON)
Mosquito Surveillance
Adult mosquito surveillance is an important component of the vector-borne disease program and involves the deployment of black-light CDC traps and BG-Sentinel 2 (BGS-2) traps at various locations throughout WEC.
The CDC traps are equipped with light and dry ice that attracts and traps the mosquitoes. These traps capture mosquitoes for testing to determine the presence of WNV and EEE in our region. BG-Sentinel 2 (BGS-2) traps are species-specific traps set up to catch invasive species of mosquitoes (Aedes albopictus and Aedes aegypti) that were identified during routine WNV surveillance in WEC in 2016. These traps use a scent lure and dry ice to attract daytime mosquitoes and are set up in high-traffic areas (near transport routes and industrial cargo areas), at commercial and residential properties. The trapped mosquitoes are sent to an accredited laboratory for identification and testing to determine if any of the mosquitoes carry the WNV, EEE or Zika virus.
The trap deployment will start on May 20, 2025, and run until mid-October. Once a week, 40 mosquito traps (25 CDC light traps and 15 BGS 2 traps) will be set up across WEC to collect mosquitoes for identification and viral testing. The weekly mosquito surveillance data will be made available on the WECHU's Mosquito Surveillance Dashboard.
Human case Surveillance
The human case surveillance program identifies human cases of WNV and Lyme disease in WEC to determine the source of the disease. Health Care Providers must report all probable and confirmed cases to the WECHU. The health unit investigates cases of WNV and Lyme disease based on case definitions developed by the Ontario Ministry of Health. Standardized case information, including demographics, symptoms, risk factors (such as travel history or having received blood products), are gathered, and entered into a provincial system. Through surveillance mechanisms the WECHU identifies clusters and geographic areas that may need targeted intervention that would include public awareness and education.
Fight the Bite! Campaign
Fight the Bite! is an annual public awareness campaign that targets priority populations with messaging focusing on the prevention of mosquito breeding sites, proper tick removal, signs and symptoms of WNV and Lyme disease, and personal protection. Additionally, when positive mosquito pools are identified through monitoring efforts, messaging and resource materials will be provided through localized door-to-door initiatives along with increased social media posts. In 2025, the WECHU will work with municipalities to develop landscape management strategies that can help to reduce tick populations in public spaces, such as parks, trails, and playgrounds. and put up trail signs to help residents identify high-risk areas and take appropriate precautions.