Epidemiological Survey of Four Reproductive Disorder Associated Viruses of Sows in Hunan Province during 2019–2021

SIMPLE SUMMARY: Porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2 (PCV2), pseudorabies virus (PRV), and classical swine fever virus (CSFV) are major causative agents contributing to the reproductive disorders in sows in China. This is the first research investigating the epidemiology and molecular characteristics of these four viruses in sows with reproductive disorders in China. In this study, 407 aborted-fetus samples were obtained from 89 pig farms in Hunan province from 2019 to 2021 for molecular detection and phylogenetic analysis of PRRSV, PRV, PCV2, and CSFV. Collectively, various patterns of singular infections or co-infections were identified in pig herds; PRRSV and PCV2, especially, were frequently detected in the collected specimens. Further phylogenetic analysis revealed the complex genotypes of each virus prevalent in pig populations in Hunan province. In conclusion, this study provides the latest information on the epidemiology and genotype diversity of four viruses in sows with reproductive diseases in Hunan province of China, which would contribute to developing effective strategies for disease control. ABSTRACT: Porcine reproductive disorders have been considered as the major factors that threaten pig industries worldwide. In this study, 407 aborted-fetus samples were obtained from 89 pig farms in Hunan province, to investigate the prevalence of four viruses associated with porcine reproductive disease, including porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2 (PCV2), pseudorabies virus (PRV), and classical swine fever virus (CSFV). Meanwhile, the target gene sequences of representative PRRSV (ORF5), PCV2 (ORF2), CSFV (E2), and PRV (gE) strains were amplified, sequenced, and analyzed. The results showed that the positive rates of PRRSV, PCV2, PRV, and CSFV among the collected samples were 26.29% (107/407), 52.83% (215/407), 6.39% (26/407), and 12.29% (50/407), respectively. Moreover, co-infection with two and three pathogens were frequently identified, with PCV2/PRRSV, PRRSV/CSFV, PRRSV/PRV, PCV2/CSFV, PCV2/PRV, and PRRSV/PCV2/CSFV mix infection rates of 9.09%, 3.19%, 2.95%, 3.69%, 2.21%, and 0.49%, respectively. Moreover, ORF5-based phylogenetic analysis showed that 9, 4, and 24 of 37 PRRSV strains belonged to the PRRSV2 lineages 1, 5, and 8, respectively. ORF2-based phylogenetic analysis revealed that PCV2d and PCV2b were prevalent in Hunan province, with the proportions of 87.5% (21/24) and 12.5% (3/24), respectively. An E2-based phylogenetic tree showed that all 13 CSFV strains were clustered with 2.1 subgenotypes, these isolates were composed of 2.1b (10/13) and 2.1c (3/13) sub-subgenotypes. A gE-based phylogenetic tree showed that all six PRV strains belonged to the genotype II, which were genetically closer to variant PRV strains. Collectively, the present study provides the latest information on the epidemiology and genotype diversity of four viruses in sows with reproductive diseases in Hunan province, China, which would contribute to developing effective strategies for disease control.