TABLE 4.
Effectiveness of immunization with avirulent serovar Abortusovis vaccine strains in ewes in protecting against pregnancy failure after challenge with wild-type serovar Abortusovis strain SS44
| Strain (group) | No. of animals | Relevant genotype | No. of abortions | No. of lambs (healthy/ deada) | % of pregnancy failure | Pc |
|---|---|---|---|---|---|---|
| SU304 (A) | 9 | aroA | 4 | 8b/0 | 44 | NS |
| SU40 (B) | 13 | Plasmid cured | 3 | 13b/0 | 23 | <0.05 |
| SSM189 (C) | 6 | crp-cya-cdt | 3 | 3/0 | 50 | NS |
| SS44 (D) | 14 | Wild type | 8 | 5/1 | 64 |
a
Lambs died within 3 weeks, and wild-type serovar Abortusovis SS44 was isolated at necropsy.
b
Certain ewes that did not abort delivered twins.
c
Chi-square analysis was used to compare abortion occurrence among immunized animals versus nonimmunized animals. NS, not significant.