2006 Surveillance for West Nile virus in Manitoba


Positive Surveillance Indicators*
Surveillance Indicator 2006* 2005 2004 2003 2002
Corvids ** __ 12 16 134 86
Mosquito Collections (Adult) 171 193 57 290 15
Horse Cases 1 4 0 47 236
Human Cases (Classified) 51 58 3 143*** 0

* As of December 7, 2006.

** The West Nile virus dead corvid pick up program was not n effect in 2006. Dead corvids are no longer needed as an early indicator of West Nile virus in Manitoba or to determine geographic distribution. Larval sampling, mosquito sampling and testing in addition to other factors (temperature, etc.) will be used to guide the assessment of risk of West Nile virus exposure.

*** Updated in 2005 after receiving a late report on a Manitoba resident with WNV who was investigated in Saskatchewan in 2003.

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Culex tarsalis Mosquito Trap Catch by Regional Health Authority 2006*
Average Adult Culex tarsalis Mosquitoes per Weekly Trap Catch
Regional Health Authority June 4-10 June 11-17 June 18-24
Assiniboine <1 <1 <1
Brandon <1 <1 <1
Central 5 3 2
Interlake 10 2 3
North Eastman 4 <1 3
Parkland 0 <1 <1
South Eastman 6 1 2
Winnipeg 13 2 1
Regional Health Authority June 25-July 1 July 2-July 8 July 9-July 15
Assiniboine 2 6 4
Brandon <1 2 8
Central 11 15 8
Interlake 14 33 24
North Eastman 5 14 9
Parkland <1 <1 0
South Eastman 4 13 13
Winnipeg 18 21 19
Regional Health Authority July 16-July 22 July 23-July 29 July 30-Aug 5
Assiniboine 8 22 136
Brandon 10 31 42
Central 9 15 15
Interlake 37 70 43
North Eastman 20 17 11
Parkland 0 <1 1
South Eastman 11 15 5
Winnipeg 50 83 98
Regional Health Authority Aug 6-Aug 12 Aug 13-Aug 19 Aug 20-Aug 26
Assiniboine 36 25 13
Brandon 47 4 5
Central 11 7 2
Interlake 32 7 1
North Eastman 9 7 1
Parkland 1 0 0
South Eastman 6 3 1
Winnipeg 64 12 4
Regional Health Authority Aug 27-Sept 2 Sept 3 -Sept 9 Sept 10 -Sept 16
Assiniboine 2 <1 <1
Brandon 2 <1 <1
Central <1 <1 <1
Interlake <1 0 <1
North Eastman <1 <1 0
Parkland 0 0 <1
South Eastman <1 0 0
Winnipeg 2 <1 <1

* As of December 7, 2006. (Routine mosquito trapping ended the week of September 10, 2006.)

Permanent mosquito traps are set up in 36 community areas in southern Manitoba to monitor Culex tarsalis mosquitoes, the mosquitoes that are most likely to transmit West Nile virus to humans in Manitoba. The above table will represent the average number of Culex tarsalis mosquitoes per trap catch for the week by Regional Health Authority (RHA) and  provides a relative measure of the activity levels of Culex tarsalis from one RHA to another and over time. This measure is an indicator as to whether Culex tarsalis mosquito populations are rising or falling or staying steady. It should be noted that these RHA averages provide an approximate indication of the number of Culex tarsalis in the RHA, counts in specific locations within the RHA will vary depending on local conditions, temperature, precipitation, etc.

Note:  Normally, two Centers for Disease Control (CDC) mosquito traps baited with carbon dioxide are run for two nights each week in each Manitoba community except Winnipeg and Brandon (where proportionately more traps are used because of larger community size). 

The average number of Culex tarsalis per trap catch (a trap catch – may also be called a “collection”- represents the mosquitoes collected by one trap during one night from approximately one hour before sunset until approximately one hour after sunrise) is calculated by dividing the total number of Culex tarsalis collected for the whole week in a given RHA by the number of collections.

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Positive Mosquito Collections (Adult) by RHA 2006
Positive Mosquito Collections (Adult) by RHA 2006
Assiniboine 34
Brandon 7
Central 7
Interlake 40
North Eastman 9
Parkland 0
South Eastman 4
Winnipeg 70
Total 171

* As of December 7, 2006.

Mosquito samples from the following communities have tested positive for WNV in 2006: Altona, Beausejour, Boissevain, Brandon, Carberry, Carman, Deloraine, East St. Paul, Gimli, Headingley, Killarney, Niverville, Oakbank, Portage la Prairie, St. Andrews, Selkirk, Sioux Valley First Nation, Steinbach, Stony Mountain, West St. Paul, Winkler, and Winnipeg.

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WNV Human Cases by Regional Health Authority 2006*

Represents the Regional Health Authority of residence of the patient.

Regional
Health
Authority

Asymptomatic

West Nile Virus Non-Neurological Syndrome

West Nile Virus
Neurological Syndrome

Under Investigation

TOTAL

Assiniboine 0 6 0 0 6
Brandon 0 0 0 0 0
Burntwood 0 1 0 0 1
Central 0 9 2 0 11
Interlake 1 5 5 0 11
N. Eastman 0 1 1 0 2
Parkland 0 0 0 0 0
S. Eastman 0 1 2 0 3
Winnipeg 0 10 7 0 17
Total 1 33 17 0 51

* As of December 7, 2006.

The most likely locations of exposure have been determined for at least one human case in each of the following municipalities: RM of Alexander, RM of Armstrong, RM of Brokenhead, RM of Cartier, RM of Clanwilliam, RM of Coldwell, RM of De Salaberry, RM of East St. Paul, RM of Louise, RM of MacDonald, Town of Morden, RM of North Cypress, RM of Pilot Mound, RM of Portage la Prairie, RM of Rockwood, RM of St. Andrews, RM of Ste. Anne, RM of St. Clements, City of Selkirk, RM of Stanley, Town of Stonewall, RM of Turtle Mountain, RM of Victoria Beach, City of Winnipeg, RM of Woodlands.

Further information on likely locations of exposure will be added as it becomes available. The risk of WNV, however, exists throughout all of southern Manitoba and is not limited to the communities listed. WNV has been identified in this or previous years within the boundaries of all regional health authorities except for NOR-MAN, Burntwood, and Churchill.

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Severity of WNV Disease By Age 2006*
Age in Years Asymptomatic West Nile Virus Non-Neurological Syndrome West Nile Virus
Neurological Syndrome
Under Investigation Total
  0 -   9 0 0 0 0 0
10 - 19 0 1 0 0 1
20 - 29 1 1 1 0 3
30 - 39 0 4 1 0 5
40 - 49 0 9 6 0 15
50 - 59 0 10 4 0 14
60 - 69 0 4 1 0 5
Over 70 0 4 4 0 8
Total 1 33 17 0 51

Average Age - West Nile Virus Neurological
Average Age - West Nile Virus Non-Neurological Syndrome: 51

* As of December 7, 2006.

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WNV Disease by Gender 2006*
Gender Asymptomatic West Nile Virus Non-Neurological Syndrome West Nile Virus
Neurological Syndrome
Under
Investigation
Total
Male 0 24 9 0 33
Female 1 9 8 0 18
Total 1 33 17 0 51

* As of December 7, 2006.

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Additional information and maps are available at the Public Health Agency of Canada website.


For WNV health concerns, contact your doctor or call:

Health Links - Info Santé
204-788-8200
(Winnipeg) or toll-free 1-888-315-9257