Porcine Circovirus Type 2 Genotypes and PCV3 in Swine Clinical Samples From Brazil

Abstract

Porcine circovirus type 2 (PCV2), an important pathogen in swine, causes PCV disease
(PCVD). Although PCVD is effectively controlled using commercial vaccines, its clinical presentation
is changing. Moreover, PCV2 is genetically evolving, with new genotypes emerging in vaccinated or
unvaccinated pigs. In this study, we aimed to verify the presence of the PCV2a, PCV2b, and PCV2d
genotypes in PCV-positive porcine samples. Furthermore, to identify coinfections between the PCV2
genotypes and/or PCV3, which can also induce disease in pigs, we employed a quick, effective, and
low-cost PCR diagnostic test. In this study, 333 PCV2 PCR and clinically positive samples from various
production stages and herds across Brazil were analyzed. Among these, 266 samples were genotyped,
with PCV2b emerging as the most predominant genotype (56.77% of the positive samples), mainly
observed in nursery pigs. PCV2d was also identified in 33.10% of the samples, primarily from finishing
pigs and breeding sows. The employed PCR test was compared with a commercial kit, proving effective
in PCV2 genotyping. This study demonstrates the significance of PCV2 genotyping, showing PCV2b as
the most predominant genotype responsible for disease in pig farms in Brazil. PCV2a, the prevalent
genotype used in commercial vaccines, was not detected in any of the analyzed samples. While pigs
infected with other PCV2 genotypes may receive some heterologous protection from PCV2a vaccines,
adequate diagnosis and vaccine monitoring for updates must be considered.