DeGroot*, M.; Baratelli, M.; Jordà, R.; Rodríguez-Ballarà, I.
*Corresponding author (firstname.lastname@example.org)
HIPRA, Amer (Girona), Spain
The protective role of specific antibodies against Swine Erysipelas (SE) and Porcine Parvovirus (PPV) enhanced through vaccination is key to control infectious reproductive problems in breeders1. Therefore, the presence of gilts and sows seronegative to SE and PPV in vaccinated farms causes great concern among farmers; this is generally considered a marker of poor vaccination practices or low vaccine efficacy2. The present study was meant to survey the serological status of mature gilts and sows on Canadian farms implementing vaccination against the above-cited pathogens.
Materials and Methods
Eleven farms vaccinating against SE, PPV and Leptospira spp. (trivalent vaccines) from Canada, located in Alberta, Ontario or Saskatchewan provinces were recruited. Sera samples were collected according to table 1; between 1 and 3 farms in each cluster do not submit any sample or those were incorrectly submitted. Samples were then tested by ELISA to determine the presence of antibodies against SE by INgezim PPV Compac (Ingenasa) and PPV by an in house assay (BIOVET, Canada). All samples were taken from breeders (gestating gilts and sows) with the complete vaccination protocol.
Table 1. Herd sampling.
Results showed presence of subpopulations of seronegative breeders in sampled farms with the highest incidence among gilts. This problem was particularly evident when the antibody response against PPV was examined. Seronegative breeders were highly present among vaccinated gilts (53.6±37.5%) and to a lesser extent among sows with 2-4 farrowing (8.3±13.5%).
Figure 1. Antibody response against PPV in sows of different parity; results are represented as average and standard deviation of the percentage of negative breeders per farm. Different letters denote a statistical significant difference (Mann-Whitney U test; p<0.05).
In contrast, the problem was less evident when the antibody response against SE was examined. Low percentage of seronegative breeders was detected and these were mostly present among vaccinated gilts (12.3±10.8%).
Figure 2. Antibody response against SE in sows of different parity; results are represented as average and standard deviation of the percentage of negative breeders per farm. Different letters denote a statistical significant difference (Mann-Whitney U test; p<0.05).
Finally, cross tables were generated to study the relationship between Erysipelas and PPV responses in gilts. Interestingly, the percentage of gilts positive to both pathogens was 29.5%. Moreover, a disagreement between PPV and SE results was found (Cohen’s kappa, k=0,031). Considering that used vaccines were trivalent, these results might suggest disequilibrium between the immune response induced by PPV and SE antigens contained in the same vaccine or a significant circulation of SE in studied farms.
Results might suggest weaknesses in currently implemented vaccination protocols in the Canadian pork industry. Therefore, vaccine’s protocols or/and vaccines used should be revised or changed.
However, the importance of the presence of these subpopulations of seronegative gilts and sows in the herd immunity needs to be elucidated.
- Shimoji Y. 2000, Microbes Infect 965-972.
- Giménez-Lirola LG. et al. 2012, J Microbiol Methods, 91: 73-79.