A Survey of Avian Polyomavirus (APV) Infection and Viral Genetic Characteristics in Taiwan during 2012-2013

• Main Authors: Yi-Hsin Lai, 賴奕欣
• Other Authors: 沈瑞鴻
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/39250706625420540790

碩士 === 國立中興大學 === 獸醫學系暨研究所 === 102 === The avian polomavirus (APV) is an acute, lethal, and highly contagious viral disease in most parrot species. Recently, the worldwide epidemiological studies of APV infection in psittacine birds were performed by PCR. In this study, we collected fecal and tissue samples from clinical cases and a breeding aviary. For APV prevalence, 443 samples from 22 genera and 41 species of psittaciform birds were checked by PCR assay. Confirmed by necropsy exam which indicated hepatomegaly with hemorrhage and swollen spleen in the sick birds. In further histopathologic exam, the characteristic basophilic intranuclear inclusion bodies could be found in karyomegalic cells in spleen, renal tubular epithelium, and liver. Based on the sequence of the VP1 gene of APV from Genbank, we designed a PCR assay with high sensitivity for APV detection. The total positive rate was 37.47% (166/443) indicating APV persistently existing in Taiwan. Multiple gene sequencing assays were performed at combined region of VP2 and VP3 and the gene encoding region of t/T antigens. The similarity of 20 isolates of VP2/3 and t/T antigen coding regions from Taiwan ranged from 98.3–100.0%. This investigation revealed that APV isolated from Taiwan was highly conserved. The sequencing results of 20 isolates in this study also indicated that there was no significant difference by comparing with worldwide sequences in the tested gene regions. However, the public conventional PCR assays for APV detection might amplify non–specific products and the sensitivity of the assays should be improved. These drawbacks could be avoided by developing the quantitative real–time PCR (qPCR) assay, which showed improved rapidity, sensitivity, reproducibility, and reduced the risks of contamination. In the current study, the qPCR assay based on SYBR Green Ⅰ fluorescence and the primer set designed at the conserved region of VP1 gene was developed. The detection limit of the qPCR assay reached 1×101 copies of viral DNA, and the assay was highly specific without amplifying any product from other avian viral and bacterial genomes (including PBFD, Chlamydia, E. coli and Salmonella Typhimurium). This newly developed qPCR is a suitable tool for rapid clinical investigations