PREPARED BY: Environmental Health

DATE: 2026-11-12

The Windsor-Essex County Health Unit (WECHU) delivers an integrated vector-borne disease surveillance and control program accordance with the Infections Disease Protocol, 2023  and West Nile Virus Preparedness and Prevention Plan. The program supports provincial requirements to assess, monitor, prevent, and reduce the burden of infectious diseases through surveillance, risk assessment, vector control, and public education. Windsor-Essex County's (WEC) location along a major international transportation corridor, combined with high cross-border travel volumes and the impacts of climate change, increases the risk of invasive vectors and emerging vector-borne diseases. Warmer temperatures, milder winters, and longer periods of vector activity are creating more favourable conditions for the introduction and establishment of species such as Aedes albopictus highlighting the need for ongoing surveillance and prevention activities.

Key program components include mosquito surveillance and larviciding, active tick surveillance, human case monitoring, and public education through WECHU’s “Fight the Bite!” campaign. Mosquito surveillance monitors populations, identifies species of public health significance, and tests for West Nile virus (WNV), Eastern equine encephalitis (EEE) virus, and Zika virus. In 2026, the WECHU added chikungunya virus (CHIKV) testing. Although CHIKV is not designated as a Disease of Public Health Significance in Ontario, this proactive enhancement responded to the Public Health Agency of Canada’s identification of WEC as an area of increased risk following the establishment of the invasive mosquito species Aedes albopictus. Tick surveillance monitors the distribution of blacklegged ticks and assesses the risk of Lyme disease and other tick-borne illnesses.

This report summarizes 2026 surveillance findings and vector control activities, highlights how these activities support provincial public health mandates, and identifies opportunities to strengthen the program in 2027.

DISCUSSION

Mosquito surveillance program ranfor 21 weeks, from May 19 to October 8, 2026. Each week, 40 traps, including 25 CDC light traps and 15 BGS-2 traps, were deployed across WEC for mosquito identification and viral testing. A total of 79,233 mosquitoes were collected, down from 92,629 in 2025, reflecting normal year-to-year variation associated with environmental and seasonal conditions. Although fewer mosquitoes were collected in 2026, WNV activity increased from 10 positive mosquito pools in 2025 to 16 in 2026. Three human WNV cases were reported in 2026, compared with seven in 2025. While WNV-positive mosquito pools increased, human case counts declined, highlighting that mosquito infection activity and human illness are influenced by multiple factors, including environmental conditions, human exposure patterns, and the uptake of preventive measures. These findings reinforce the importance of continued surveillance, timely risk communication, and personal protective measures to reduce disease risk.

As part of a comparative study, seven 3-D traps supplied by the Public Health Agency of Canada (PHAC) were added to assess their performance relative to BGS-2 traps. The 3-D traps collected 7,505 mosquitoes and generated data on trap performance, species composition, and operational requirements. A detailed study summary will be presented to the Board of Health in February 2027.

Surveillance also documented further expansion of Aedes albopictus, with 439 specimens collected—nearly four times the 110 specimens collected in 2025. No CHIKV-, EEE-, or Zika-positive mosquito pools or related human cases were identified in 2026.

Note: For 2026, the data includes 7505 mosquitoes caught in 3-D traps.

Mosquito larviciding program: Larviciding involves applying chemical or biological agents to catch basins, standing-water sites, and lagoons where mosquitoes may breed, preventing larvae from developing into adults. WECHU contracts a service provider to support municipalities with larvicide treatment from May to September. In 2026, approximately 135,000 roadside catch basins received three rounds of treatment.

Active tick surveillance: The WECHU conducts tick dragging twice annually, in spring and fall, to monitor tick distribution and identify the pathogens they may carry. Sites are selected using the Public Health Ontario blacklegged tick established-risk-area map, historical surveillance findings, and community submissions through eTick. Together, these sources support early detection and monitoring of emerging risk areas.

In May and September 2026, tick dragging was conducted at four sites across WEC. No blacklegged ticks were identified during either period. Dog ticks collected in May were submitted to the National Microbiology Laboratory through a provincial initiative monitoring for Rocky Mountain spotted fever; no dog ticks were detected during fall surveillance. To date, 21 human Lyme disease cases have been reported in 2026, compared with 14 cases in 2025. 

Although no blacklegged ticks were detected through scheduled tick dragging activities, this does not rule out their presence elsewhere in WEC or exposures acquired through travel to areas where established tick populations exist. As tick dragging is conducted at a limited number of locations and is intended primarily as an early risk assessment tool, the absence of ticks at surveillance sites should not be interpreted as the absence of tick-borne disease risk across the region. The increase in reported Lyme disease cases highlights the continued importance of surveillance, public education, and personal protective measures as blacklegged tick populations and Lyme disease risk continue to expand across Ontario.

The 2026 findings support a risk-based approach to program delivery in 2027. Proposed enhancements are intended to improve operational efficiency and resource use, and focus activity on the areas of greatest public health value.

2027 Planned Program Enhancements

• Continue CHIKV testing and enhanced monitoring of Aedes albopictus to identify changes in local distribution and disease risk.
• Use the 3-D trap evaluation to inform the future mosquito-trap mix, deployment approach, and operational requirements.
• Continue risk-based tick surveillance using provincial risk mapping, historical findings, and community submissions to guide site selection.
• Maintain timely public education and prevention messaging when surveillance or human case data indicate increased risk.

These enhancements will support a sustainable, evidence-informed approach to monitoring and responding to emerging vector-borne disease risks in WEC.