Abstract
Porcine circovirus type 2 (PCV2) is one of the major swine viral diseases and caused significant economic loss to pig producers worldwide, including Taiwan. PCV2 has been considered as the causative agent of postweaning multisystemic wasting syndrome (PMWS) as well as other clinical diseases. All these associated syndromes have been categorized as PCV2 associated diseases (PCVAD). The purpose of this study was to investigate the positive rate and genetic shift of two distinct genotypes of PCV2, which include PCV2a and PCV2b, in Taiwanese pig farms. A total of 1094 specimens originating from pigs between years 1999 and 2016 were analysed. The PCV2a and PCV2b sequences were amplified and distinguished using 1oop-mediated isothermal amplification (LAMP). Results showed that 24.8% (272/1094) pigs were PCV2a positive, 67.3% (737/1094) were PCV2b positive. These results also indicated that PCV2a was the predominant virus between 1999 and 2001, and that PCV2b became the most prevalent virus since 2003.
Highlights
Porcine circovirus type 2 (PCV2) is a member of the genus Circovirus within the family Circoviridae [1, 2]
For evaluating the analytical specificity of loop-mediated isothermal amplification (LAMP), 36 virus isolates were used, comprising eight PCV2a, 11 PCV2b, four PCV type 1 (PCV1), two porcine parvovirus (PPV), three pseudorabies virus (PrV) and eight porcine reproductive and respiratory syndrome virus (PRRSV), and all of the isolates were identified by determining their partial nucleotide sequences as previously studies [9, 21]
The deoxyribonucleic acid (DNA) of PCV2a, PCV2b, PCV1, PPV, and PRV and the complementary DNA of PRRSV isolates were produced as previously studies [9, 21], and stored at – 20°C until use or used immediately for this study
Summary
Porcine circovirus type 2 (PCV2) is a member of the genus Circovirus within the family Circoviridae [1, 2]. The ORF1 encodes two major replication associated proteins: the complete Rep, and the spliced form Rep, which has a frame shift Rep′ [1]. ORF2 encodes the capsid protein (Cap), which contains the immunodominant antigenic epitopes, and has been used as a target for vaccine development [2, 4]. Some variable amino acid residues located in the putative epitopes of ORF2 are exposed outside the virion, and these residues are suggested to be constantly under positive or negative selection forces due to constant exposure to high immunologic pressure [2, 4]. The ORF3 encodes a protein that has been implicated with cellular apoptosis in the porcine kidney PK-15 cell line, as well as in peripheral blood mononuclear cells [3]
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