- 3 minutes, 9 seconds
- Expertise article
- J Stadler, S Zoels, M Eddicks, A Ladinig, C Kraft, M Ritzmann
INTRODUCTION
Porcine Reproductive and Respiratory Sydrome Virus (PRRSV) is considered to be one of the major pathogens in pigs and causes significant economic impact on the swine industry worldwide. PRRSV vaccination has been demonstrated as an effective tool to control clinical signs related to PRRSV infection. The aim of the present study was to evaluate field efficacy of PRRS genotype 1 modified live virus vaccine (PRRS 94881 MLV) in sows and gilts at various stages of gestation.
MATERIALS AND METHODS
The study was conducted in a piglet producing farm with 660 sows. On study day - 1 (D-1) a total of 505 sows and gilts were included in the study. Sows and gilts were ear tagged and randomly allocated to group 1 (n=235) and group 2 (n=270). At the time of inclusion, 10% of sows and gilts from each study group were randomly assigned as sample animals. The study groups were housed in separated barns with separate air spaces. Animals in both study groups were kept under similar conditions in terms of climate, ventilation, temperature and air humidity. On study day 0 sows of group 1 were vaccinated with 2mL of the Control product (CP), a commercial modified live PRRSV genotype 1 vaccine according to the manufactures instructions. Sows of group 2 were administered intramuscularly with 2 mL of the Investigational Veterinary product (IVP), a modified live-virus PRRS Genotype 1 vaccine (PRRS 94881 MLV). To prevent cross contamination between the two vaccination groups separation of housing was maintained for at least five weeks post vaccination. To assess the efficacy of the IVP reproductive performance parameter were recorded from all sows/gilts till D119. The number of piglets alive per litter at weaning was selected as the primary criterion for the evaluation of vaccine efficacy. Farrowing performance (healthy live born piglets, weak born piglets, stillborn piglets, mummies and crushed piglets per litter), the abortion rate and returned to service were selected as secondary parameters. To evaluate piglet performance, piglets from sample animals were ear tagged and body weight was recorded at farrowing and at weaning. Piglets from sample animals were blood sampled at weaning to determine viremia by using an inhouse quantitative real-time PCR assay (qRT-PCR).
RESULTS
The mean total number of piglets alive at weaning did not differ significantly between group 1 and group 2, however the percentage of piglets alive at weaning was significantly higher in the IVP (89.1%) than in the CP (85.9%) group (p=0.005). A significant difference was detected between both groups for number of piglets per litter that died during the suckling period (p= 0.008). Piglet mortality was significantly lower in the IVP group compared to the CP group. Examination of farrowing performance data for both groups resulted in no statistical differences between groups for percentage or number of alive, healthy live, weak piglets, stillborn, mummified, and crushed piglets per litter at farrowing. No differences were detected between both groups for piglet birth weights, however, least square (LS) mean average daily gain was significantly higher in the IVP group (245g) compared to the CP group (221g) (p= 0.037). As a result, LS mean body weights at weaning were significantly higher in the IVP group (7.2kg) compared to the CP group (6.6 kg) (p= 0.026). The mean proportion of viremic piglets per litter at weaning did not differ significantly between both groups.
Table 1: Mortality of piglets during the suckling period [%];
Table 2: Body weight at farrowing and weaning, ADG of piglets [kg];
LSMean values with 95 % confidence intervals, ns: not significant, p > 0.05;
DISCUSSION AND CONCLUSION
Reproductive performance, survival rate, and piglet growth performance observed in the present study support the efficacy of PRRS 94881 MLV at various stages of gestation.
REFERENCES
- Lunney et al. (2010) Virus Res. 154: 161-169.
- Holtkamp et al. (2013) Journal of Swine Health and Production 21: 72-84.
- Scortti et al. (2006) Theriogenology 66: 1884-1893.