Importance: Pandemics involving the porcine reproductive and respiratory syndrome virus (PRRSV) impact swine health and productivity, causing economic devastation, especially in large-scale feeding areas.
Objective: This study examined the prevalence and genetic variations of PRRSV in Chengdu, China, a vital transportation hub and the main area of pig breeding in southwest China, between January 2021 and December 2022.
Methods: The samples were collected from 13 key pig-feeding areas in Chengdu. The positive PRRSV samples were detected using a real-time quantitative polymerase chain reaction. The genetic variations of the PRRSV were analyzed by amplifying the open reading frame 5 (ORF5) gene and comparing it with relevant reference sequences.
Results: The PRRSV positive rate in Chengdu was 11.42% (276/2,416), including sublines 8.7, 5.1, 3.0, and 1.8. The ORF5 gene sequences in the samples had no insertion or deletion of amino acids but widespread variations, including the 13th and 151st positions, which were associated with viral virulence.
Conclusions and relevance: The PRRSV pandemic in Chengdu was relevant, and recombination between vaccine strains and field strains can contribute to vaccine immune failure.
Keywords: ORF5 gene; PRRSV; epidemics; genetic evolution.
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