May 2021 Board of Health Meeting - Vector-Borne Surveillance Report Information Report

Meeting Document Type
Information Report
Vector-Borne Surveillance Report


May 2021


Vector-Borne Surveillance Report 


The Environmental Health Department conducts annual monitoring and testing of tick and mosquito populations in Windsor and Essex County (WEC) as part of the WECHU’s Zoonotic and Vector-borne Diseases Program. The program is required under the Health Protection and Promotion Act and provides the community with an early warning system for disease transmission through ticks and mosquitoes known as vector-borne diseases. Due to our geography and local climate, the WEC region is more susceptible to vector-borne diseases, as the ecological conditions influence transmission and distribution. 

Ticks and Lyme Disease

The Windsor Essex County Health Unit (WECHU) monitors tick-borne disease risk in our region. In the last three years, surveillance data indicated an increase in black-legged ticks (Ixodes scapularis) in WEC. The black-legged tick is the primary vector for Borrelia burgdorferi, the bacteria that causes Lyme Disease.

Environmental Health staff conduct active field surveillance at public parks and trails frequently used by community members and is done twice yearly to identify areas in WEC that have populations of black-legged ticks. In 2020, active field surveillance was not completed due to the COVID-19 pandemic, but it will resume this year in the following areas,

  • Chrysler Greenway
  • Ojibway Prairie Nature Reserve
  • Gesstwood Camp
  • Ruscom Shores Conservation Area

In 2020, the submission of ticks to the WECHU through passive surveillance was discontinued. The data collected from previous years has allowed the health unit to determine where and how the community have been exposed to ticks. The health unit will continue with suspending passive tick surveillance and will no longer accept tick specimens going forward.  Members of the public are recommended to submit a photograph to, a free online service. The service will be promoted this year through WECHU’s website and social media channels.

Human Cases

In 2020, there were four cases of Lyme Disease in WEC.  All laboratory-confirmed cases are interviewed to determine where they may have encountered black-legged ticks. This information drives targeted tick awareness initiatives from the health unit.

Mosquito Surveillance and Testing

The WECHU, has one of Ontario’s most comprehensive mosquito surveillance programs. In 2020, mosquito surveillance began in May and ended in early October. Species-specific traps were deployed in various locations throughout WEC to capture mosquitoes for testing and identification to determine the presence of West Nile, Eastern Equine Encephalitis (EEE) Virus, and Zika Virus in our region. Invasive mosquito species Aedes aegypti (Yellow Fever Mosquito) and Aedes albopictus (Asian Tiger Mosquito) were also monitored through our Enhanced Mosquito Surveillance Program. These species are known carriers of diseases such as Zika, Malaria, Dengue, and Chikungunya. The health unit monitors mosquitoes at different stages in their life cycle to determine prevention and control initiatives for the program.

During this year’s season:

  • Total number of traps deployed per week: 47
  • Total number of mosquitoes trapped: 205,569
  • Total number of pools tested: 2,052
  • Number of positive pools for West Nile Virus : 30
  • Number of positive pools for Zika Virus: 0
  • Number of positive pools for EEE Virus: 0

The WECHU was the successful recipient for a grant from the Public Health Agency of Canada to study the effects of climate change and mosquito populations in our local communities. For the 2020 season, an additional 14 traps were strategically placed in Leamington to monitor mosquito populations. In addition to surveillance activities, key informant interviews were conducted to better understand the health care needs of the local community and within under-served populations (e.g., Temporary Foreign workers), identify gaps that exist in meeting those needs, and strengthen community involvement to improve health care access. All analysis of interview data has been completed, and an interview summary report will be released in June 2021.

Mosquito Control

Over 135,000 treatments of larvicide were applied to roadside catch basins and standing water sites last year to control mosquito populations. All municipalities in WEC have standing water by-laws that should be enforced due to the high number of positive West Nile Virus (WNV) pools in our region. Furthermore, property standards by-law enforcement is key to controlling invasive mosquito populations in our region, as these mosquitoes are container breeders.

Human Cases

The WECHU follows up on all human cases of WNV. Cases are investigated to assess if additional mosquito control activities are required. In 2020, there were two confirmed and one probable case of WNV in WEC. To date, there have been no human cases of Zika Virus identified in our community.


The WECHU will begin surveillance and monitoring activities for ticks and mosquitoes in May 2021. In addition to these activities, the WECHU will be launching a Fight the Bite public awareness campaign in June 2021. The awareness campaign will focus on the prevention of mosquito breeding sites, information on tick removal, signs and symptoms of WNV and Lyme Disease, and personal protection. Messages and promotional materials will be developed to reach priority populations and inform the public of hot spots identified through previous monitoring efforts.

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