Evaluation of PRRS piglet vaccination in a multi-origin nursery unit in Spain

Introduction

Vaccination against the porcine reproductive and respiratory syndrome virus (PRRSV) is widely used to prevent production losses in the swine industry.

With regard to piglets, vaccination against PRRS has been shown to be a useful and profitable measure to not only decrease PRRS infection pressure in the nursery phase but also to provide reasonable protection for piglets, that is usually seen as a reduction in mortality¹. This is especially important in the current scenario of the Spanish swine industry where since the appearance of highly pathogenic PRRSV strains, primary and secondary infections by agents such as Influenza virus, Glaesserella parasuis, Actinobacillus pleuropneumoniae, Streptococcus suis or Pasteurella multocida have increased due to the immunosuppression that this virus causes, acting as a gateway that can seriously worsen the health status of the animals².

In this study, the efficacy of piglet vaccination was assessed in a multi-origin nursery unit in the southeast of Spain.

Materials and Methods

The study was carried out in a post-weaning unit located in one of the most densely populated pig production areas in Spain. It received 850 weekly weaned piglets from 3 different origins (O1: 700 sows, O2: 650 sows and O3: 800 sows).

All 3 source farms were stable for PRRS, proven by a negative PCR result from serum samples of weaned piglets. When piglets from the different origins were moved to post-weaning, they became PRRS positive at 8-9 weeks of age with Ct values varying between 30-35. This positivity was reflected in an increased mortality rate from 2.5% to 5%.

To reduce this horizontal virus circulation and its impact on production, piglets were vaccinated against PRRS with Unistrain® PRRS IM at 3 weeks of age, when entering the nursery phase.

To analyse the effects of vaccination, the mortality during the nursery phase of vaccinated animals from the 3 different origins (n = 35 672) was recorded over a period of 6 months and compared with the mortality in the previous 3 months of unvaccinated piglets (n = 17 836). Differences were tested using the Wilcoxon Test.

Results

After the introduction of PRRS piglet vaccination, the mortality rate was reduced in the vaccinated piglets from 3 different origins, significantly in O1 and O2, decreasing from 2.63% to 1.82% (p-value = 0.028) and from 6.07% to 4% in 02 (p-value = 0.024). The reduction in the mortality of the piglets from the third origin (O3) went from 4.89% to 4.05% with a p-value of 0.067.

Figure 1 – Mortality rate (%) in nursery phase vaccinated and non-vaccinated animals, divided by origin.

Discussion and Conclusion

The results obtained show the effectiveness of PRRS piglet vaccination applied at the correct time as a tool to reduce mortality in a multi-origin nursery phase. Vaccination is just one of the pillars of a complete PRRS control strategy that should be complemented by other measures such as biosecurity, management, and monitoring measures.

Read more publications about PRRS Control

References

1. Valdes-Donoso et al. Combining epidemiology and economics to assess control of a viral endemic animal disease: Porcine Reproductive and Respiratory Syndrome (PRRS). PLoS One. 2022 Sep 9;17(9).
2. Saade, G., Deblanc, C., Bougon, J. et al. Coinfections and their molecular consequences in the porcine respiratory tract. Vet Res 51, 80 (2020). https://doi.org/10.1186/s13567-020-00807-8.