- 3 minutes, 13 seconds
- Expertise article
- J Stadler, S Zoels, M Eddicks, A Ladinig, C Kraft, M Ritzmann et. al.
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. An individual examination for clinical signs was performed daily, starting the day before vaccination till D14. Clinical observation score included an assessment of behavior, respiratory signs and digestion. Additionally rectal temperatures were measured from sample animals on D-1, D0+1h, +4h till D14. Local reactions at the injection site were investigated from sample animals on study day 0, 1h and 4h post vaccination and subsequently daily till 14 days post vaccination. Injection sites were examined for redness, swelling, heat and pain during palpation. Blood samples were collected from sample animals on D-1, D14, D28, D84 and D119 to determine viremia by using an in-house quantitative real-time PCR assay (qRT-PCR).
RESULTS
Clinical observation revealed no significant differences between both study groups, regarding frequency and degree of the clinical signs behavior and respiration. In contrast, reduced feed intake was less frequently observed in sows from the IVP group (11.5% vs. 21.3%; p=0.003) compared to sows from the CP group from D1 till D14. Mean rectal temperatures post-treatment ranged from 38.0 °C to 38.9°C and from 37.9°C to 38.7°C for the CP and IVP groups, respectively. Rectal temperatures exceeded 40°C for more than one day in one sample animal of the CP group and two sample animals from the IVP group. No significant differences per time point between groups were detected for rectal temperatures. Local injection site reactions were observed in sows and gilts from both groups between D0 (+1h) and D14. Injection site reactions were significantly less frequent in the IVP group compared to the CP group for pain (0% vs. 16.7%; p= 0.039), redness (57.1% vs. 87.5%; p= 0.030), heat (0% vs. 20.8%; p= 0.016) and swelling (25.0% vs. 70.8%; p= 0.002). The average duration of local reactions was 5.7 and 2.8 days in the CP and IVP group, respectively. One sow from the CP group showed reddening and swelling at the injection site on 12 days following the injection of the vaccine. The average swelling size was 4.4 and 2.5 cm for the CP and IVP groups, respectively.
The maximum swelling size was reported with 20 cm in the CP group (severe score) and 8 cm in the IVP group (moderate score). All sow and gilt serum samples from sample animals were negative for the detection of PRRSV by qPCR at all scheduled time points during the study.
Figure 1: Local reactions in sows [number of animals with at least one abnormal finding post vaccination] from day 0 till day 14
DISCUSSION AND CONCLUSION
Local or systemic reactions were less frequently observed in pigs receiving the IVP than in those receiving a registered PRRS vaccine, therefore supporting the field safety of PRRS 94881 MLV in sows and gilts 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.