Virus isolation, sequence analysis and epidemiological survey for avian leukosis virus from Taiwan Country chickens and egg-type chickens in Taiwan
Date Issued
2010
Date
2010
Author(s)
Chang, Shu-Wei
Abstract
Avian leukosis viruses (ALVs) are common in many poultry flocks and can cause neoplastic diseases and other reproductive problems in chickens. Based on differences in their envelope glycoproteins, ALVs are divided into six subgroups (A, B, C, D, E, and J). Subgroup A (ALV-A), B, C, D and J (ALV-J) are considered exogenous, whereas subgroup E encompasses the endogenous viruses. Because the eradication of ALV has not carried out in Taiwan Country chicken industry, the purpose of this study is to investigate the profile of exogenous ALV infection in Taiwan Country chickens by virus isolation, sequence analysis, and molecular and serologic surveillance. 5 recombinant ALVs and 2 subgroup J ALVs were isolated from 5 Taiwan Country chicken farms with no tumor occurrence, and the full proviral DNA genomes of isolates ALV TW-3577 and ALV TW-3593 were sequenced, analyzed and compared with representative strains of ALV. Isolate ALV TW-3577 possessed a myeloblastosis-associated virus 1 gp85 coding region and an ALV-J 3’ untranslated region (3’UTR) and long terminal repeat (LTR); the LTR, gag, pol, gp37 coding region, and the3’UTR of ALV TW-3593 displayed high identity to endogenous counterpart sequence, and the gp85 coding region of ALV TW-3593 was different from all the subgroups, with a moderate nucleotide sequence identity to ALV-C (88.1%). In this study, we designed a primer (TWA) for molecular detection of exogenous ALVs except ALV-J. 61 Taiwan Country chicken farms from slaughter house, 2 layer farms, and one Taiwan Country broiler breeder farm were screened for exogenous ALVs by PCR, for ALV-A/B and ALV-J antibody by enzyme-linked immunosorbent assay (ELISA), and for group-specific antigen (GSA) by ELISA. ALV TW-3593-like viruses and ALV-J were detected in 60 and 43 farms of 61 Taiwan Country chicken farms, respectively. The broiler breeder farm was also positive for ALV TW-3593-like viruses. ALV-J antibodies was detected in the plasma samples of 28 Taiwan Country chicken farms with moderate positive rates (10-60%), while only 6 Taiwan Country chicken farms and the broiler breeder farm had ALV-A/B antibodies, and the positive rates of these farms were quite low (10-20%). These two layer farms were negative for exogenous ALVs by PCR and ALV-A/B, ALV-J antibodies by ELISA. The GSA tested by ELISA showed significantly difference between serum and plasma samples collected from the same flocks, the positive rate of serum samples was extremely higher than plasma samples (P < 0.01). Our results reveal that there are at least two recombinant ALVs circulating in Taiwan flocks. In addition, dual infection with ALV TW-3593-like viruses and ALV-J are common in this study, indicating that ALV TW-3593-like viruses are the most prevalent ALV in Taiwan Country chicken population.
Subjects
avian leukosis virus
virus isolation
sequence analysis
recombinant
exogenous virus
PCR
Taiwan Country chicken
epidemiological survey
Type
thesis
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