Table 2. Positive rates of serum antibodies to Yersinia outer membrane protein in domestic pigs in Chiba prefecture, Japan by year.
| Sampling Year | No. of Yersinia positive samples/ No. of samples tested (%) |
No. of Yersinia positive pig farms/ No. of pig farms tested (%) |
||
|---|---|---|---|---|
| 2017 | 44 / 80 | (55.0)a | 13 / 16 | (81.3) |
| 2018 | 32 / 80 | (40.0)b | 11 / 16 | (68.8) |
| 2019 | 52 / 80 | (65.0)c | 13 / 16 | (81.3) |
| 2020 | 61 / 240 | (25.4) | 16 / 23* | (69.6) |
| 2021 | 57 / 170 | (33.5) | 15 / 16* | (93.8) |
| Total | 246 / 650 | (37.8) | 70 / 89 | (78.7) |
The χ2 test and Fisher’s exact test were used to calculate significant differences. a 2017 greater than 2020 and 2021 (P<0.05). b 2018 greater than 2020 (P<0.05). c 2019 greater than 2018, 2020 and 2021 (P<0.05). *Some farms were sampled in duplicate.