Volume 16, Number 3—March 2010
Research
Surveillance for West Nile Virus in American White Pelicans, Montana, USA, 2006–2007
Gregory P. Johnson
, Nicole M. Nemeth, Kristina Hale, Nicole P. Lindsey, Nicholas A. Panella, and Nicholas Komar
, Nicole M. Nemeth, Kristina Hale, Nicole P. Lindsey, Nicholas A. Panella, and Nicholas Komar
Table 2
Culex tarsalis mosquito infection data for WNV calculated weekly during 2 WNV transmission seasons, Medicine Lake National Wildlife Refuge, Montana, USA*
| Week of collection | 2006 |
2007 |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| Light trap nights | Light trap index ± SD† | No. positive pools/no. tested | Light trap nights | Light trap index ± SD† | No. positive pools/no. tested | Infection rate‡ (95% CI) | Vector index§ (95% CI) | ||
| Jul 1–7 | 13 | 4.1 ± 4.3 | 0/17 | 4 | 448.5 ± 549.5 | 0/100 | 0.0 | 0.0 | |
| Jul 8–14 | 9 | 6.6 ± 11.6 | 0/59 | 9 | 325.3 ± 131.4 | 5/800 | 6.3 (0.8–11.7) | 2.0 (0.3–3.8) | |
| Jul 15–21 | 10 | 9.0 ± 8.8 | 0/88 | 10 | 1,643.0 ± 899.8 | 7/1,000 | 7.0 (1.8–12.2) | 11.5 (3.0–20.0) | |
| Jul 22–28 | 11 | 7.0 ± 5.9 | 0/69 | 8 | 259.6 ± 301.9 | 4/1,000 | 4.0 (0.1–7.9) | 1.0 (0.03–2.1) | |
| Jul 29–Aug 4 | 13 | 7.1 ± 10.4 | 0/74 | 7 | 169.0 ± 105.3 | 10/937 | 10.7 (4.1–17.3) | 1.8 (0.7–2.9) | |
*WNV, West Nile virus: CI, confidence interval.
†Light trap index is mean number of adult female Cx. tarsalis mosquitoes collected per trap night. Seven traps were used in 2006, and 5 traps were used in 2007.
‡Infection rate is in units of 1,000 mosquitoes and determined by maximum-likelihood estimate. Infection rate was 0 for all collection dates in 2006.
§Vector index is the product of light trap index and infection rate. Unit of measure is number of infected female Cx. tarsalis mosquitoes per trap night. Vector index values were 0 for all collection weeks in 2006.
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