PREPARED BY:
Environmental Health
DATE:
May 18, 2023
SUBJECT:
Zoonotic and Vector-borne Disease Surveillance Program
BACKGROUND/PURPOSE
The Environmental Health Department delivers a zoonotic and vector-borne surveillance program to monitor Rabies, West Nile Virus (WNV), Eastern Equine Encephalitis (EEE), Zika Virus and Lyme disease activity in Windsor and Essex County (WEC). 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 as well as to prevent human cases of rabies by animal rabies surveillance. This program is made up of the following components: mosquito larval surveillance and larviciding; adult mosquito trapping; human case surveillance for Rabies, WNV and Lyme disease; animal bite investigation; public education; and active tick surveillance. 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
Animal Bite Investigations
Rabies is a viral disease that affects the central nervous system of warm-blooded animals, including humans. Once symptoms appear, rabies is almost always fatal. In Canada, bats, foxes, skunks, and raccoons are the most common transmitters of the disease.
All potential rabies exposure cases are required to be reported to WECHU and are initiated within 24 hours of notification. Investigation includes an assessment of rabies risk in the animal species, the behaviour of the animal implicated, confinement of animals, and ensuring individuals requiring treatment have access to rabies post exposure prophylaxis.
In 2022, a total of 858 rabies cases were investigated and followed up by the Public Health Inspectors. Almost 94% of these exposures were from canine and feline species.
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.
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. Tick dragging is performed twice yearly in the spring and the fall.
In 2022, tick dragging was conducted at 4 sites across WEC (Ojibway Prairie Nature Reserve, Chrysler Greenway, Gesstwood Camp and Education Centre, and Ruscome Shores Conservation Area) in spring and fall. One Lone star tick and 21 blacklegged ticks were found through tick dragging. This year tick dragging will be conducted during the months of May and September.
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. 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.
In 2022, 90,000 mosquitoes were caught, and 12 pools tested positive for West Nile virus. For 2023, the trap deployment will start on May 23rd, and run until mid-October. Once a week, 41 mosquito traps (26 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. Physicians and hospitals must report all probable and confirmed cases to the WECHU.
The health unit investigates all suspected, probable and confirmed WNV and Lyme disease cases among WEC residents based on case definitions developed by the Ministry of Health (MOH). Standardized medical information, including demographics, symptoms, risk factors (such as travel history or having received blood products) and test results, are entered into the MOH's Integrated Public Health Information System (iPHIS). Through case interviews and GIS mapping, the health unit identifies clusters and geographic areas that may need targeted intervention.
Fight the Bite! Campaign
Fight the Bite! Public awareness campaign will launch in July 2023. It will focus on the prevention of mosquito breeding sites, information on tick removal, signs and symptoms of WNV and Lyme disease, and personal protection.