Studies on infectious bursal disease virus.

摘要

Infectious bursal disease virus (IBDV) causes an acute and contagious disease in young chickens from 3--6 weeks of age. Two serotypes of the virus are recognized of which serotype 1 viruses are pathogenic to chickens and are classified into classic, variant, and serotype 2 viruses are nonpathogenic. The disease is controlled by vaccination. In the first part of the study interactions between a mild and a pathogenic strain of IBDV in specific pathogen free (SPF) chickens were studied. Chickens were inoculated with the Bursine-2 vaccine followed by the pathogenic STC strain at various time intervals. Persistence of virus strains was monitored by the reverse transcriptase polymerase chain/restriction fragment length polymorphism (RT-PCR/RFLP), bursa/body weight ratios and histopathological lesion scores. The mild strain interfered with the replication of the pathogenic strain.; Currently available ELISA kits were evaluated for their ability to detect antibodies elicited by serotype 1 and serotype 2 viruses. Virus neutralization (VN) test differentiates between antibodies elicited by the two serotypes as well as subtypes of serotype 1 viruses. SPF chickens were inoculated with either serotype 1 STC or serotype 2 OH strain. Sera from these chickens and naturally exposed chickens were tested by five commercial ELISA kits and the VN. The ELISA kits detected antibodies to both serotypes of the virus. Therefore, while determining the antibody profiles of the flocks, the presence of serotype 2 antibodies should be taken into account.; Simple and quick diagnostic assays are needed for developing control strategies against IBDV. A differential RT-PCR assay was developed. Two primer sets were designed. Primer set one targeted the segment A of the virus and specifically amplified serotype 2 strains. Primer set 2 targeted the segment B of the virus and amplified the vv strains. These primer sets were validated with 26 different strains maintained in our laboratory. The primer set 2 was also tested with 20 suspected vv field isolates. All except three samples tested positive with primer set 2. The Taiwan strains appeared genetically similar to the classic viruses upon sequencing.