A single recall vaccination lapse in sows triggers PRRSV resurgence and boosts viral genetic diversity

• DOI: 10.1186/s40813-025-00433-w
• Publication Date: 2025-05-08T16:24:09Z
• Authors: H. Clilverd; G. E. Martín-Valls; Y. Li; I. Domingo-Carreño; M. Martín; M. Cortey; E. Mateu
• Keywords: Flock; Attenuated vaccine

Abstract Background Porcine reproductive and respiratory syndrome virus (PRRSV) persists on certain farms despite vaccination control efforts, with genetic diversity suspected as a contributing factor. This study examined the evolution persistence dynamics of PRRSV-1 farrow-to-fattening farm 1,700 sows vaccinated quarterly, focusing summer lapse. Results Over eight months, three farrowing batches were monitored from birth to nine weeks age using virological (RT-qPCR, whole-genome, ORF5 sequencing) serological (ELISA neutralizing antibody) analyses. An incident related elevated temperatures during involving unproper vaccine handling occurred last blanket vaccination, before sampling third batch. Viral circulation was primarily confined nurseries, notable surge incidence mortality in this batch, linked lower maternal antibody levels likely due failure. Phylogenetic analyses showed same viral strain throughout study, increased Batch 3 driven by selection recombination. Ultimately, reestablishing program led PRRSV-positive-stable status. Conclusions Overall, single lapse caused weaners, declining levels, underscoring importance strict adherence.