- 1 minute, 46 seconds
- Expertise article
- Dürlinger S., Balka G., Rathkjen PH., Kraft C., Morgenstern R., Rümenapf T., Ladinig A. et.al.
INTRODUCTION
Porcine reproductive and respiratory syndrome virus (PRRSV) is still one of the economically most important viruses in the swine industry and is often combatted by the use of modified live virus vaccines (MLV). The aim of the present study was to establish an infection model in weaned piglets to recreate symptoms observed in the field and, in addition, to show if the MLV vaccine “Ingelvac PRRSFLEX® EU” was able to improve weight gain and reduce lung lesions in vaccinated piglets after experimental infection with PRRSV strain AUT15-33 in comparison to non-vaccinated piglets.
MATERIALS AND METHODS
Vaccinated (Ingelvac PRRSFLEX® EU) and non-vaccinated piglets at four weeks of life (D0) were intranasally infected with a low dose (1x103 TCID50) or a high dose (1x105 TCID50) of PRRSV AUT15-33 at D28 (Table 1). One additional group of ten vaccinated piglets served as vaccination control group (vacc ctrl). Body weight was recorded for calculating average daily weight gain (ADG). Serum samples were collected to assess the viremia levels by qRT-PCR (Fig. 1)
Table 1. Group assignment
Figure 1. Study design
RESULTS
ADG from D28 to D42 was highest in vacc ctrl. ADG of vaccinated infected pigs differed numerically from non-vaccinated infected pigs (Fig. 2). The infection with PRRSV AUT15-33 led to long lasting viremia in all inoculated piglets. Delayed titer increase was measured in vaccinated infected pigs compared to non-vaccinated infected pigs as well as in low dose infected piglets compared to high dose infected piglets (Fig. 3a & 3b). Nevertheless, on D39 all infected pigs reached approximately same viremia levels. Macroscopic and histologic lung lesions were significantly lower in vacc ctrl pigs compared to all infected groups and even lower in vaccinated compared to non-vaccinated pigs (Fig. 4).
Figure 2. Average daily weight gain (adg) before and after PRRSV challenge
Figure 3a. Mean and standard deviation of qRT-PCR results of each group at different time points
Figure 3b. Genome equivalents (log10)/ml serum of each animal post challenge
Figure 4. Total histo score
CONCLUSION
In this study the PRRSV strain AUT15-33 reproducibly caused clinical disease and viremia. Vaccination of piglets with PRRS MLV had a positive effect on ADG and reduced severity of lung lesions after experimental PRRSV infection in our study.