Table 3.
Number of commercial broiler chicken flocks sampled at processing between July 2010 and January 2012 in Ontario, Canada stratified by enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) test results for avian reovirus (n = 231 flocks); the average flock mortalitya per stratum is provided
| ELISA mean titer | PCR positiveb | Average (range) flock mortality (%) | PCR negative | Average (range) flock mortality (%) |
|---|---|---|---|---|
| 5000 to 5999 | 1 | 3.1 | 0 | — |
| 4000 to 4999 | 2 | 3.2 (0.8 to 5.7) | 0 | — |
| 3000 to 3999 | 2 | 3.0 (2.4 to 3.5) | 2 | 3.0 (2.9 to 3.2) |
| 2000 to 2999 | 8 | 3.9 (2.3 to 7.6) | 5 | 4.8 (2.2 to 9.4) |
| 1000 to 1999 | 18 | 3.6 (0.3 to 6.3)c | 22 | 3.5 (1.7 to 6.4)g |
| 500 to 999 | 31 | 3.6 (0.6 to 5.8)d | 26 | 3.6 (1.3 to 7.6)h |
| 397 to 499 | 14 | 3.3 (0.8 to 8.9)e | 15 | 4.4 (2.1 to 6.4)i |
| 0 to 396 | 44 | 3.2 (1.9 to 5.5)f | 41 | 3.4 (0.6 to 12.7)j |
For each flock, mortality was estimated as the number of chicks placed minus the number of birds shipped, divided by the number of chicks placed, and multiplied by 100. For each stratum, average mortality was calculated as the sum of flock mortality in the stratum divided by the number of flocks in the stratum.
The total number of samples tested per flock using PCR was 6 (3 pooled samples of caecal tonsil tissues and 3 pooled samples of cloacal swabs); if ≥ 1 of 6 samples tested positive, the flock was considered to be PCR-positive.
Due to missing mortality data the number of flocks used for the calculations were c16 of 18, d23 of 31, e11 of 14, f37 of 44, g18 of 22, h23 of 26, i14 of 15, j38 of 41.