Genotype Detection of Circovirus Type 2 (PCV2) in Swine Clinical Samples from Brazil

Abstract

Abstract Porcine circovirus disease (PCVD) is one of the most impactful diseases in commercial pig production. It is caused by the infection of a small, circular DNA virus, porcine circovirus type 2 (PCV2). Currently, four types of PCV have been identified: PCV1, PCV2, PCV3, and PCV4. PCV2 is classified into 9 different genotypes (a-i). Although there is widespread use of commercial vaccines for PCV2 and PCVD is not a new disease, its presentation has changed. In addition, PCV2 has also evolved genetically, requiring monitoring of vaccinated herds for clinical and genotypic aspects. The objective of this study was to identify genotypes of PCV2, namely, PCV2a, PCV2b, and PCV2d. Additionally, the study aimed to identify coinfections of different PCV2 genotypes and PCV3 coinfections. Herein, 333 PCVD clinical samples of pigs that tested positive for PCV2 from various tissues, states in Brazil, and production phases were analyzed. Of those, 266 were genotyped, and PCV2b was the most frequent genotype found in 56.77% of positive samples, mainly in nursery samples. However, PCV2d was present in 33.10% of the samples, mainly from finishing pigs and breeding sows. The PCR used in this study was compared to a commercial kit and was effective in PCV2 genotyping. This study shows that it is important to genotype PCV2, and conventional PCR demonstrated a good option for this. PCV2b remains the most prevalent in pig farms in Brazil and continues to cause disease. It is necessary to state that in Brazil, the most commonly used commercial vaccines are for PCV2a. Even though PCV2a vaccines provide heterologous protection for other genotypes, the adequate diagnosis and study of the need for updating vaccines for the genotypes currently circulating must be considered.