| Summary: | 碩士 === 國立屏東科技大學 === 獸醫學系所 === 105 === Porcine circovirus type 2 (PCV2) is a causative agent of PCV2-associated disease (PCVAD), which leads to continuously enormous economic losses in the swine industry worldwide. According to the database from Animal Disease Diagnostic Center of National Pingtung University of Science and Technology (ADDC of NPUST) during 2014 to 2016 in Taiwan, the PCV2 positive rate in suckling pigs was 36.6% to 52.3%, nursery pigs was 43.2% to 51.1%, and growing pigs was 58.7% to 78.6%. The results showed that the PCV2 still has a significant impact on Taiwan. In order to more understand the epidemiology of PCV2 in Taiwan. The PCV2 ORF2 sequences collected from 60 PCVAD cases during 2016 to 2017 in ADDC of NPUST were analyzed. Meanwhile, the PCV2 ORF2 sequences of 108 isolates from 2001 to 2015 in Taiwan and 46 isolates from different PCV2 genotypes in different countries were compared in this study. Phylogenetic analysis indicated that the PCV2b-1C, novel PCV2b and mutant PCV2b emerged in Taiwan during 2001 to 2015 were referred as PCV2d. Also, PCV2b, PCV2d-1 and PCV2d-2 could be traced back to 2001, 2006 and 2008, respectively. By now, PCV2d-2 has become a predominant genotype of PCV2 in Taiwan. According to the analysis of the 168 Taiwanese PCV2 ORF2 nucleotides, the lowest identity among PCV2a, PCV2b and PCV2d-2 were 92%, 95.2% and 97.3%, respectively. Also, the analysis of putative amino acid of PCV2 ORF2, the lowest identity among PCV2a, PCV2b and PCV2d-2 were 90.2%, 91.9% and 94.9%, respectively. Besides, the putative amino acid of PCV2 ORF2 among all the 168 Taiwanese PCV2 isolates were also discussed. The results showed that the amino acid residues 89 played a role in dividing PCV2a, PCV2b and PCV2d as isoleucine (I), arginine (R) and leucine (L), respectively, in this study. Moreover, the residues 53, 59, 68, 134, 169, 191, 206, 232 and 234 had been found differences in properties of amino acids substituted between PCV2a and PCV2d-2 in this study. Which could be attributed to escape from the immune response during the prolonged circulation in a highly immune population. However, the further research of cross-protection between different PCV2 genotypes associated with amino acids substitution are needed.
|
|---|
