2004 Surveillance for West Nile virus in Manitoba


Positive Surveillance Indicators 2004
Surveillance Indicator 2004* 2003 2002
Corvids 16 134 86
Mosquito Collections (Adult) 57 290 15
Horse Cases 0 47 236
Human Cases 3 143** 0

* As of September 16, 2004

** 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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WNV Patients by Regional Health Authority 2004*

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

2

0 0 2
Brandon 0 0 0 0 0
Central 0 0 0 0 0
Interlake 0 0 0 0 0
N. Eastman 0 0 0 0 0
Parkland 0 0 0 0 0
S. Eastman 0 0 0 0 0
Winnipeg 0 0

1

0 1
TOTAL

0

2

1

0 3

* As of September 16, 2004

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Severity of WNV Disease By Age (Ave. Age 51; Age Range 14–92) 2004*
Age in Years Asymptomatic West Nile Virus Non-Neurological Syndrome West Nile Virus
Neurological Syndrome
Under
Investigation
Total
Less than 30 0 1 0 0 1
30 - 39 0 0 0 0 0
40 - 49 0 1 0 0 1
50 - 59 0 0 0 0 0
60 - 69 0 0 1 0 1
Over 70 0 0 0 0 0
Totals 0 2 1 0 3

*As of September 16, 2004

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WNV Disease by Gender 2004*
Gender Asymptomatic West Nile Virus Non-Neurological Syndrome West Nile Virus
Neurological Syndrome
Under
Investigation
Total
Male 0 1 1 0 2
Female 0 1 0 0 1
Total 0 2 1 0 3

*As of September 16, 2004

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Corvid Surveillance by Regional Health Authority 2004*

Regional Health Authority

Number of birds
submitted for testing

Number of birds
that tested positive

Winnipeg 142 7
Parkland 16 1
Interlake 37

2

Assiniboine 24 1
Central 30 1
North Eastman

41

1

South Eastman

20

3

Brandon 20 0
Nor-Man

12

0
Burntwood

10

0
Churchill

0

0

Total

352

16

* As of September 16, 2004

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Birds from the crow family (corvids) are very susceptible to WNV. Many die soon after becoming infected. Testing dead crows and other corvids provides an early indication of the presence of infected mosquitoes in an area.


Culex tarsalis Mosquito Trap Catch by Regional Health Authority 2004*
Average Adult Culex tarsalis Trap Catch Summary by RHA
Culex tarsalis Sept 5 -
Sept 11
Aug. 29 -
Sept 4
August 22 -
August 28
Assiniboine ** 0 1
Brandon ** 1 1
Central 0 0 3
Interlake 0 0 0
North Eastman 0 0 0
Parkland 0 0 0
South Eastman 0 0 1
Winnipeg 2 1 1
Culex tarsalis August 15 - August 21 August 8 - August 14 August 1 - August 7
Assiniboine 11 17 284
Brandon 1 4 84
Central 3 2 39
Interlake 2 1 10
North Eastman 0 1 4
Parkland 1 8 11
South Eastman 10 2 36
Winnipeg 32 32 68
Culex tarsalis July 25 -
July 31
July 18 -
July 24
July 11 -
July 17
Assiniboine 215 292 93
Brandon 237 21 35
Central 186 27 30
Interlake 8 10 1
North Eastman 127 16 5
Parkland 62 6 2
South Eastman 289 70 20
Winnipeg 115 39 192
Culex tarsalis July 4 -
July 10
June 27 -
July 3
June 20 -
June 26
Assiniboine ** 1 0
Brandon ** 0 0
Central 5 3 0
Interlake 1 1 0
North Eastman 0 0 0
Parkland ** 0 0
South Eastman 4 1 0
Winnipeg 0 0 1

* As of September 16, 2004. Final averages subject to change based on incoming data.
** Trapping not underway during this period

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Permanent mosquito traps will be set up in 30 sites 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 represents 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 or three Centers for Disease Control (CDC) mosquito traps baited with carbon dioxide are run for one or 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.


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