Serotype specificity of Porcilis PRRS
For effective protection pigs should be vaccinated with the predominant serotype found in the region.
Cross-protection experiments
The level of viraemia after challenge in unvaccinated pigs is 100%.
| Group | Challenge with a European serotype | % Viraemia |
|---|---|---|
| 1 | Unvaccinated pigs | 100% |
| 2 | Pigs vaccinated with Porcilis PRRS | 14.8% |
| 3 | Pigs vaccinated with North American serotype vaccine | 88.6% |
| Group | Challenge with an American serotype | % Viraemia |
|---|---|---|
| 1 | Unvaccinated pigs | 100% |
| 2 | Pigs vaccinated with Porcilis PRRS | 84.3% |
| 3 | Pigs vaccinated with North American serotype vaccine | 17.9% |
Total viraemia after PRRSV challenge with different serotypes
(Labarque et al. 2004)
For effective vaccination it is better to know which field virus serotype predominates and to vaccinate with that serotype. There are reports that some cross-protection between serotypes does occur but experience shows that vaccination with a homologous strain is more effective than vaccination with a heterologous strain.
Effect on viraemia of an American and a European serotype PRRSV vaccine after challenge with European wild-type strains of the virus
P.A.M van Woensel, K. Liefkens, S. Demaret
Veterinary record (1998)142, 510-512
Method
Three groups of 10 pigs were vaccinated with an North American serotype PRRSV vaccine and three groups of 10 pigs were vaccinated with a European type PRRSV vaccine. A control group of 12 pigs were left unvaccinated.
Four weeks after vaccination the PRRSV-specific antibody titres were determined. The serological response confirmed that the two vaccines were of different serotypes.
Four weeks after vaccination each group was challenged with either a Spanish (S1) , German (DI3) or Dutch (I2) PRRSV wild-type strain.
Results and conclusion
The integrated titres of challenge viruses after challenge over 14 days are shown in the graph below.
Integrated titres of viraemia challenge with three different European PRRSV (I2, S1 and D13) strains observed in control pigs(C) and in pigs vaccinated with either a North American (A) or a European (E) serotype PRRSV strain.
Vaccination with the North American serotype vaccine hardly reduced the level of viraemia after challenge with the European PRRSV strains, only after challenge with the Spanish PRRSV strain was a moderate statistically significant reduction in viraemia observed. In contrast, after vaccination with the European serotype vaccine, viraemia was completely suppressed after challenge with the German PRRSV isolate and almost completely suppressed after challenge with the Dutch and Spanish isolates.
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