Table 2.
Results of enzyme immunoassays (antibody blocking [ELISA] and PRNT) conducted on sera from American White Pelican chicks that were < 3 weeks old and chicks that were near to fledging
| Year and study area | < 3-week-old chicks (June) | Near-fledged chicks (August) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| n | ELISA | PRNT | Antibodies to WNV (%) | 95% CI | n | ELISA | PRNT | Antibodies to WNV (%) | 95% CI | |
| 2006 | ||||||||||
| Chase Lake | 52 | 5 | 5 | 10 | 2, 18 | 50 | 11 | 10 | 20 | 9, 31 |
| Bitter Lake | 46 | 1 | 0 | 0 | 50 | 28 | 25 | 50 | 36, 64 | |
| Medicine Lake | 50 | 3 | 0 | 0 | 50 | 11 | 11 | 22 | 10, 34 | |
| 2007 | ||||||||||
| Chase Lake | 52 | 0 | 0 | 0 | 28 | 18 | 18 | 64 | 45, 83 | |
| Bitter Lake | 50 | 2 | 2 | 4 | 0, 10 | 27 | 17 | 20 | 74 | 56, 92 |
| 2008 | ||||||||||
| Chase Lake | 50 | 9 | 8 | 16 | 5, 27 | 4 | 0 | 0 | –* | – |
| Bitter Lake | 50 | 3 | 2 | 4 | 0, 10 | 50 | 22 | 22 | 44 | 30, 58 |
All provisionally positive samples (ELISA results) were tested with PRNT to confirm the presence of antibody to WNV. Data were collected at Chase Lake, North Dakota; Bitter Lake, South Dakota; and Medicine Lake, Montana. Each year, observation of diseased chicks first occurred in mid-July and peaked in late July. 95% CI = 95% confidence interval.
*
Sample size too small for calculation of meaningful proportion.