First detection of PCV4 in pigs in the USA – Abstracts

Since PCV4 was first described in 2019, the virus has been identified in a number of countries in Southeast Asia and Europe. Most studies were limited to detection of PCV4 by PCR. Thus, PCV4 has an unclear relationship with clinical disease.

Methods: This study used 512 clinical samples of lung, feces, spleen, serum, lymphoid tissue, and fetal pigs submitted to ISU-VDL from June to September 2023.

Results: PCV4 was detected in 8.6% of samples with a mean Ct value of 33. Although detection rates varied between sample types, lymphoid tissue had the highest detection rate (18.7%). Two ORF2 sequences were obtained from lymphoid tissue samples with 96.36–98.98% nucleotide identity to the reference sequences. Direct detection of PCV4 using RNAscope revealed viral replication in B cells and macrophages in lymph node germinal centers, as well as histiocytic and T cell infiltration in the lamina propria of the small intestine. Detection of PCV4 was more often observed in fattening pigs with respiratory and intestinal diseases. Co-infection with PCV2, PCV3 and other endemic pathogens was frequently observed, highlighting the complex interactions between different PCVs and their potential role in disease pathogenesis.

Conclusion: This study provides information on the detection frequency, tissue distribution, and genetic characteristics of PCV4 in the United States.

Kroeger M, Vargas-Bermudez DS, Jaime J, et al. First detection of PCV4 in pigs in the United States: co-detection with PCV2 and PCV3 and direct detection in tissues. Scientific reports. 2024; 14:15535 https://doi.org/10.1038/s41598-024-66328-y