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The Windsor-Essex County Health Unit (WECHU) conducts mosquito surveillance from mid-May until mid-October every year. Once a week, 47 mosquito traps are set across Windsor and Essex County (WEC) to collect mosquitoes for identification and viral testing. The Health Unit collects, compiles, and analyzes information on mosquito-borne disease activity in WEC and produces this weekly report during the mosquito season.

In Ontario, under the Ontario Public Health Standards (Ministry of Health), each health unit is required to implement a local vector-borne disease management strategy. This program includes controlling mosquito populations by larviciding catch basins, standing water sites, and lagoons in WEC. Additionally, the WECHU conducts adult mosquito surveillance and investigates human cases in the region.

The CDC light traps (developed by the U.S. Centers for Disease Control) are set up at 19 locations throughout WEC to capture mosquitoes for identification and testing to determine the presence of West Nile Virus (WNV) and Eastern Equine Encephalitis (EEE) virus in the area. These traps have a light and dry ice that attracts the mosquitoes. The mosquitoes caught are sent to a certified laboratory for identification and viral testing.

In 2016, multiple tropical species of mosquitoes (Aedes albopictus and Aedes aegypti) were identified during routine WNV surveillance in Windsor and Essex County (WEC). This led to the development of the Enhanced Surveillance Program by the WECHU. As part of this program, BG-Sentinel 2 (BGS-2) traps are set up at 14 locations throughout WEC. These traps use a scent lure and dry ice to attract daytime mosquitoes. The traps are set up in high traffic areas (such as near transport routes and industrial cargo areas) as well as in residential homes. The Aedes albopictus or Aedes aegypti captured are tested for the presence of WNV or Zika virus. Additionally, 3 to 5 ovitraps are set up at each BGS-2 trap location to monitor Aedes breeding.

The Heath Unit has received a federal grant  from the Public Health Agency of Canada’s Infectious Disease and Climate Change Program (August 2019 to March 2022)  to study the effects of climate change and mosquito populations in our local communities.  Additional traps (seven CDC light traps and seven BGS-2 traps) will be placed in Leamington to monitor Aedes albopictus and Aedes aegypti populations as part of this grant.

This weekly report contains information regarding number and type of mosquitoes caught, viral testing of mosquitoes, number of positive WNV, EEE and Zika positive pools, and number of human WNV, EEE and Zika virus cases in the area.

Summary

Total traps

  • A total of 47 traps were laid out across municipalities of WEC
    • 26 CDC light traps were deployed
    • 21 BGS-2 traps were deployed

Trap catches

  • A total of 992 mosquitoes were captured from 47 traps across the municipalities of WEC (average mosquitoes caught per trap: 21.1; range: 0 to 203) (Table 1 and Figure 1)
  • 26 CDC light traps caught 568 mosquitoes with an average of 21.8 mosquitoes caught per trap (range: 0 to 200)
    • No Cq. pertubans were caught in CDC traps
    • An average of 2.4 Cx. pipiens/restuans were caught per trap
    • An average of 10.1 Ae. vexans vexans were caught per trap
    • No Cs. melanura were caught in CDC traps 
  • 21 BGS-2 traps caught 424 mosquitoes with an average 20.2 mosquitoes caught per trap (range: 0 to 203)
    • An average of 0.2 Ae. albopictus mosquitoes were caught per trap
    • No Ae. aegypti mosquitoes were caught in the BGS-2 traps

Viral testing

  • 0 positive WNV pools were detected in the 47 traps deployed in WEC (Table 1 and Figure 1)
  • 0 positive Zika pools were detected in the 47 traps deployed in WEC (Table 1 and Figure 1)
  • 0 positive EEE pools were detected in the 47 traps deployed in WEC (Table 1 and Figure 1)

Human cases

  • 0 human cases of WNV were reported (Table 2)
  • 0 human Zika virus infections were reported (Table 2)
  • 0 human EEE virus infections were reported (Table 2)

Table 1: WEC black-light CDC trap and BGS-2 traps results - Week 42

Municipality

Amherstburg

Essex

Kingsville

Lakeshore

LaSalle

Leamington

Tecumseh

Windsor

Total

Traps

4

4

3

2

2

14

1

17

47

Total mosquitoes

36

10

13

8

10

720

9

186

992

Cx. pipiens/ restuans

7

4

6

5

0

29

4

42

97

Ae. vexans vexans

6

1

2

3

3

272

0

60

347

Cq. perturbans

0

0

0

0

0

0

0

0

0

Cs. melanura

0

0

0

0

0

0

0

0

0

Ae. albopictus

0

0

0

0

0

0

0

5

5

Ae. aegypti

0

0

0

0

0

0

0

0

0

WNV positive pools

0

0

0

0

0

0

0

0

0

Zika positive pools

0

0

0

0

0

0

0

0

0

EEE positive pools

0

0

0

0

0

0

0

0

0

Note: 2 CDC traps had malfunctioning lights and 1 BGS trap had a battery malfunction

Table 2: WEC Human WNV, EEE and Zika cases, 2020

Reported Week

Number of confirmed & probable WNV cases

Number of confirmed & probable EEE cases

Number of confirmed & probable Zika cases

21

0

0

0

22

0

0

0

23

0

0

0

24

0

0

0

25

0

0

0

26

0

0

0

27

0

0

0

28

0

0

0

29

0

0

0

30

0

0

0

31

0

0

0

32

0

0

0

33

0

0

0

34

1

0

0

35

1

0

0

36

0

0

0

37

0

0

0

38

0

0

0

39

0

0

0

40

0

0

0

41

0

0

0

42 0 0 0

Total

2

0

0

Mosquitoes captured and WNV, Zika and EEE positive pools detected, Windsor and Essex County, 2020

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