2005 Surveillance for West Nile virus in Manitoba
- Positive Surveillance Indicators
- Corvid Surveillance by Regional Health Authority
- Culex tarsalis Mosquito Trap Catch by Regional Health Authority
- Positive Mosquito Collections (Adult) by RHA
- WNV Patients by Regional Health Authority
- Severity of WNV Disease by Age
- WNV Disease by Gender
Positive Surveillance Indicators
| Surveillance Indicator | 2005* | 2004 | 2003 | 2002 |
| Corvids | 12 | 16 | 134 | 86 |
| Mosquito Collections (Adult) | 193 | 57 | 290 | 15 |
| Horse Cases | 4 | 0 | 47 | 236 |
| Human Cases | 58 | 3 | 143** | 0 |
* As of December 9, 2005.
** Updated in 2005 after receiving a late report on a Manitoba resident with WNV who was investigated in Saskatchewan in 2003.
Corvid Surveillance by Regional Health Authority 2005*
Regional Health Authority |
Number of birds |
Number of birds |
Winnipeg |
35 |
1 |
Parkland |
3 |
1 |
Interlake |
38 |
2 |
Assiniboine |
18 |
1 |
Central |
30 |
3 |
North Eastman |
16 |
1 |
South Eastman |
22 |
1 |
Brandon |
9 |
2 |
Nor-Man |
3 |
0 |
Burntwood |
5 |
0 |
Churchill |
0 |
0 |
Total |
179 |
12 |
* As of September 30, 2005. (Corvid surveillance ended on this date.)
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 2005*
| Average Adult Culex tarsalis Mosquitoes per Weekly Trap Catch | |||
| Regional Health Authority | June 5 - 11 | June 12 - 18 | June 19 - 25 |
| Assiniboine | 0 | 0 | 1 |
| Brandon | 0 | <1 | 1 |
| Central | <1 | <1 | 10 |
| Interlake | <1 | <1 | 11 |
| North Eastman | 0 | 0 | 23 |
| Parkland | 0 | 0 | <1 |
| South Eastman | <1 | <1 | 25 |
| Winnipeg | <1 | <1 | 31 |
| Regional Health Authority | June
26 - July 2 |
July
3 - July 9 |
July
10 - July 16 |
| Assiniboine | 4 | 4 | 270 |
| Brandon | 5 | 6 | 229 |
| Central | 28 | 40 | 2118 |
| Interlake | 9 | 6 | 478 |
| North Eastman | 4 | 4 | 231 |
| Parkland | <1 | <1 | 23 |
| South Eastman | 23 | 15 | 1429 |
| Winnipeg | 31 | 12 | 2210 |
| Regional Health Authority | July
17 - July 23 |
July
24 - July 30 |
July
31 - Aug. 6 |
| Assiniboine | 562 | 1289 | 416 |
| Brandon | 367 | 205 | 1359 |
| Central | 854 | 944 | 1342 |
| Interlake | 484 | 356 | 439 |
| North Eastman | 356 | 185 | 211 |
| Parkland | 59 | 37 | 47 |
| South Eastman | 1158 | 605 | 997 |
| Winnipeg | 1670 | 1847 | 1602 |
| Regional Health Authority | August
7 - August 13 |
August
14 - August 20 |
August 21 - August 27 |
| Assiniboine | 943 | 70 | 10 |
| Brandon | 718 | 35 | 4 |
| Central | 944 | 142 | 6 |
| Interlake | 218 | 22 | 1 |
| North Eastman | 314 | 20 | 1 |
| Parkland | 89 | 6 | <1 |
| South Eastman | 482 | 77 | 3 |
| Winnipeg | 823 | 115 | 4 |
| Regional Health Authority | August
28 - September 3 |
September
4 - September 10 |
|
| Assiniboine | 2 | <1 | |
| Brandon | 3 | <1 | |
| Central | 4 | 3 | |
| Interlake | <1 | <1 | |
| North Eastman | <1 | <1 | |
| Parkland | 0 | 0 | |
| South Eastman | <1 | 1 | |
| Winnipeg | 5 | 7 | |
* As of September 10, 2005. (Routine mosquito trapping
ended on this date.)
Permanent mosquito traps are set up in 30 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 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.
Positive Mosquito Collections (Adult) by RHA 2005
| Positive Mosquito Collections (Adult) by RHA 2005* | July
10 - July 16 |
July
17- July 23 |
July
24- July 30 |
July
31- Aug. 6 |
| Assiniboine | 1 | 3 | 11 | 6 |
| Brandon | 0 | 1 | 2 | 2 |
| Central | 7 | 2 | 3 | 6 |
| Interlake | 0 | 1 | 1 | 3 |
| North Eastman | 0 | 0 | 1 | 2 |
| Parkland | 0 | 0 | 1 | 0 |
| South Eastman | 1 | 4 | 2 | 14 |
| Winnipeg | 4 | 3 | 2 | 5 |
| Total | 13 | 14 | 23 | 38 |
| Positive Mosquito Collections (Adult) by RHA 2005* | August
7- August 13 |
Aug.
14 - Aug. 20 |
Aug. 21 - Aug. 27 | Aug. 28 - Sept. 3 |
| Assiniboine | 24 | 17 | 2 | 0 |
| Brandon | 0 | 0 | 1 | 0 |
| Central | 16 | 9 | 0 | 0 |
| Interlake | 3 | 1 | 0 | 0 |
| North Eastman | 4 | 0 | 0 | 0 |
| Parkland | 3 | 0 | 0 | 0 |
| South Eastman | 11 | 3 | 0 | 1 |
| Winnipeg | 5 | 3 | 0 | 1 |
| Total | 66 | 33 | 3 | 2 |
| Positive Mosquito Collections (Adult) by RHA 2005* | Sept.
4- Sept. 10 |
|||
| Assiniboine | 1 | |||
| Brandon | 0 | |||
| Central | 0 | |||
| Interlake | 0 | |||
| North Eastman | 0 | |||
| Parkland | 0 | |||
| South Eastman | 0 | |||
| Winnipeg | 0 | |||
| Total | 1 | |||
* As of September 10, 2005. (Routine mosquito trapping ended on this date.)
Mosquito samples from the following communities have tested
positive for WNV:
Altona, Beausejour, Boissevain, Brandon, Carberry, Carman,
Deloraine, East St. Paul, Killarney, Morden, Morris, Neepawa,
Niverville, Oakbank, Roblin, Russell, Sandy Bay First Nations,
St. Andrews, Ste. Anne, Selkirk, Souris, Steinbach, Stonewall,
Stony Mountain, West St. Paul, Winkler, Winnipeg, Virden.
WNV Human Cases by Regional Health Authority 2005*
Represents the Regional Health Authority of residence of the patient.
| Regional Health Authority |
Asymptomatic |
West Nile Virus Non-Neurological Syndrome |
West Nile Virus |
Under Investigation |
TOTAL |
| Assiniboine | 0 | 12 | 3 | 0 | 15 |
| Brandon | 0 | 3 | 1 | 0 | 4 |
| Central | 1 | 10 | 1 | 0 | 12 |
| Interlake | 0 | 4 | 1 | 0 | 5 |
| N. Eastman | 0 | 2 | 0 | 0 | 2 |
| Parkland | 0 | 0 | 0 | 0 | 0 |
| S. Eastman | 1 | 2 | 0 | 0 | 3 |
| Winnipeg | 1 | 12 | 4 | 0 | 17 |
| Total | 3 |
45 |
10 |
0 | 58 |
* As of December 9, 2005.
West Nile Related Deaths: In 2005, there was one human death related to a West Nile virus infection in Manitoba.
Severity of WNV Disease By Age 2005*
| Age in Years | Asymptomatic | West Nile Virus Non-Neurological Syndrome | West
Nile Virus Neurological Syndrome |
Under Investigation | Total |
| 0 - 9 | 0 | 2 | 0 | 0 | 2 |
| 10 - 19 | 0 | 2 | 1 | 0 | 3 |
| 20 - 29 | 0 | 1 | 0 | 0 | 1 |
| 30 - 39 | 0 | 9 | 1 | 0 | 10 |
| 40 - 49 | 1 | 14 | 2 | 0 | 17 |
| 50 - 59 | 1 | 9 | 3 | 0 | 13 |
| 60 - 69 | 1 | 4 | 2 | 0 | 7 |
| Over 70 | 0 | 4 | 1 | 0 | 5 |
| Total | 3 | 45 | 10 | 0 | 58 |
Average age (West Nile virus
Neurological Syndrome): 52
Average age (West Nile virus Non-Neurological Syndrome): 46.3
* As of December 9, 2005.
WNV Disease by Gender 2005*
| Gender | Asymptomatic | West Nile Virus Non-Neurological Syndrome | West Nile Virus Neurological Syndrome |
Under Investigation |
Total |
| Male | 2 | 19 | 7 | 0 | 28 |
| Female | 1 | 26 | 3 | 0 | 30 |
| Total | 3 | 45 | 10 | 0 | 58 |
* As of December 9, 2005.
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
