Table. Antibodies against Yersinia enterocolitica O:3 in blood samples and culture of feces from pigs in a closed system of 16 SPF herds in Norway*.
| Herd no. (year established) | Serologic testing (1996–2007), no. pos/no. tested | Culture (2005–2006), no. pos./no. tested |
|---|---|---|
| 1 (1996) | 10/397† | 0/20 |
| 2 (1999) | 0/150 | 0/20 |
| 3 (1997) | 1/61 | 0/21 |
| 4 (1997) | 0/19 | 0/20 |
| 5 (1998) | 0/30 | NA‡ |
| 6 (1999) | 0/34 | 0/20 |
| 7 (1999) | 0/20 | 0/20 |
| 8 (2000) | 0/60 | 0/20 |
| 9 (2001) | 0/30 | NA‡ |
| 10 (2002) | 1/61 | 0/20 |
| 11 (2002) | 0/20 | 0/20 |
| 12 (2003) | 0/30 | 0/22 |
| 13 (2003) | 0/51 | 0/18 |
| 14 (2004) | 15/30 | 11/24§ |
| 15 (2004) | 0/50 | 0/23 |
| 16 (2004) | 0/30 | 0/20 |
*SPF, specific pathogen–free. Herds 1 and 2 are nucleus herds. Herds 3–16 were established with gilts from 1 or both of the nucleus herds. A basic cut-off of optical density of 20% was used to maximize the specificity of the ELISA. †During the first 5 years, 10 of 174 blood samples from pigs in herd 1 had a low level of antibodies against Y. enterocolitica O:3 (OD >20 but <31). None of the 223 blood samples taken from pigs in this herd from 2002 through 2007 was positive. The low-positive reactions from pigs in herd 1 might have been the result of nonspecific reactions because a few of these samples were from old sows, which might have more serologic interference. ‡NA, not applicable; no culture of feces. §Positive for Y. enterocolitica O:3/biovar 4.