Comparative efficacy of Ingelvac PRRS MLV against a heterologous PRRSV 1-7-4 challenge

  • 10 minutes
  • Expertise article
  • R. Philips, G. Haiwick, D. Whiteman, B. Fergen, J. Hermann
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R. Philips, G. Haiwick, D. Whiteman, B. Fergen, J. Hermann

Boehringer Ingelheim Animal Health, Duluth, Georgia, USA

 

Introduction

The use of INGELVAC PRRS vaccines can significantly reduce lung lesions following challenge with heterologous isolates (86- 94% ORF5 nucleotide similarity) in the three-week-old pig respiratory challenge model.1 INGELVAC PRRS MLV demonstrated heterologous protection against challenge with current PRRSV lineage-1 RFLP 1-7-4 and 1-3-4 isolates.2 The objective of this study was to evaluate the efficacy of two commercially available PRRSV vaccines in a three-week-old pig respiratory challenge model, using a heterologous PRRSV lineage-1 RFLP 1-7-4 field strain that was isolated in 2016.

Materials and Methods

At approximately three weeks of age (Day 0 of the study), 108 PRRSV naïve piglets pigs were randomized into groups, and intramuscularly vaccinated with 2 ml of either a placebo (challenge controls n=36), INGELVAC PRRS MLV (n=36) or 1 ml intramuscularly of a competitor PRRS vaccine* (n=36). Pigs were housed in rooms by group during the vaccination period. At day 27 of the study (D27), all pigs were comingled and challenged with 2.0 mL intramuscularly and 2.0 mL intranasally (1 mL per nostril) with 104.6 TCID50/mL of PRRSV RFLP 1-7-4. Serum samples, weights and temperatures were collected periodically from D0 through termination of the study on D42. On D42 (14 days post-challenge), all pigs were necropsied and lungs were scored for the presence of macroscopic lesions. Serum samples were tested by RT-PCR for the presence of viremia and by ELISA for the presence of anti-PRRSV antibody. Data were analyzed using Generalized and Linear Mixed Models. Pairwise comparisons between groups were conducted using a level of confidence of 0.05 to indicate statistical significance.

Results

Table 1 summarizes lung lesions (percentage) for each group. Table 2 summarizes average daily weight gain (ADWG) for the pre-challenge and the post-challenge period of the study by group. *Prevacent® PRRS, Elanco Animal Health, Greenfield, Indiana

Table 1: Day 42 Percent Lung Lesions (mean)

Table 1: Day 42 Percent Lung Lesions (mean)
*Different letters indicate significant (P≤0.05) differences

 

Table 2: Pre and Post-challenge ADWG (lbs)

Table 2: Pre and Post-challenge ADWG (lbs)
*Different letters indicate significant (P≤0.05) differences

 

Conclusion

An objective of this study was to evaluate the efficacy of INGELVAC PRRS MLV and a competitor vaccine against a current heterologous PRRSV 1-7-4 isolate in a respiratory challenge model. There was no difference in ADWG between vaccinated and placebo groups during the pre-challenge period of the study. Both vaccines demonstrated heterologous protection by significantly reducing lung lesions, and significantly improving ADWG compared to placebo vaccinated pigs. Pigs vaccinated with INGELVAC PRRS MLV had significantly higher post-challenge ADWG compared to the competitor vaccinated group. This study further confirms the ability of INGELVAC PRRS MLV to protect against a relevant and contemporary PRRSV lineage-1 challenge.

References

  1. Patterson, A., et al. 2013. Proc Leman Swine Conf.
  2. Patterson, A., et al. 2019. J Vaccines Vaccin 10:407.