Viremia and shedding of PRRSV AUT15-33 (“acro” PRRSV) by vaccinated and nonvaccinated piglets

  • 10 minutes
  • Expertise article
  • Dürlinger S., Balka G., RathkjenPH., Kraft C., Morgenstern R., Knecht C., Zaruba M., Rümenapf T., Ladinig A.
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Dürlinger S.1, Balka G.2, RathkjenPH.3, Kraft C.4, Morgenstern R.5, Knecht C.1, Zaruba M.6, Rümenapf T.6, Ladinig A.1

1University Clinic for Swine, University of Veterinary Medicine Vienna, Austria; 2Department of Pathology, University of Veterinary Medicine Budapest, Hungary; 3Boehringer Ingelheim Vetmedica GmbH, Ingelheim, Germany; 4Boehringer Ingelheim Veterinary Research Center GmbH & Co. KG, Hannover, Germany; 5Boehringer Ingelheim Regional Center Vienna, Austria; 6Institute of Virology, Department for Pathobiology, University of Veterinary Medicine Vienna, Vienna, Austria

 

Introduction

The aim of the present study was testing of the efficacy of Ingelvac PRRSFLEX EU in decreasing viremia levels and viral shedding in piglets after a challenge with a virulent PRRSV-1- isolate (PRRSV AUT15-33) causing severe clinical problems in the field.

Material and Methods

Material and Methods Vaccinated and non-vaccinated piglets (4 groups, n=16 per group) were intranasally infected with a low dose (1x10^3 TCID50) or a high dose (1x10^5 TCID50) of PRRSV AUT15-33 28 days post vaccination (study day 28). Serum samples and oral swabs were collected at different time points (study days 0, 14, 21, 28, 31, 33, 35, 37, 39, 42, 49, 56, 63, and 70) throughout the study to assess the viremia levels and viral shedding by qRT-PCR.

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Table 1: group assignment.

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Figure 1: Timeline of the experiment. Study days on the top, age of the animals in weeks below.

Results

Viral load in serum increased in all infected piglets after challenge. Slower increase was measured in the low dose infected groups than in the high dose infected groups. Viral load of the respective non-vaccinated group increased faster compared to the vaccinated group. On study day 39 all infected pigs reached approximately same viremia levels. All infected animals shed virus in oral fluids. There was a significant reduction in the AUC of PRRSV RNA load in oral swabs of vaccinated, low dose infected pigs compared to non-vaccinated, low dose infected pigs (p < 0.05) as well as between vaccinated and non-vaccinated high dose infected pigs.

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Figure 2: Mean and standard deviation of qRT PCR results of serum samples of each group at different time points (study days)

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Figure 3: Mean and standard deviation of qRT PCR results of the oral swabs of each group at different time points (study days). Significant differences between AUC values are indicated.

Conclusion

All infected animals reached approximately same viremia levels post challenge and all animals shed virus through oral fluids. Nevertheless, vaccinated infected groups shed less virus than the non-vaccinated animals. Furthermore, the duration of shedding was lower in vaccinated pigs than in non-vaccinated pigs.