Field strains of infectious bursal disease virus (IBDV) discovered in Hong Kong

Abstract

Infectious bursal disease virus (IBDV) destroys the proliferating lymphocytes in the bursae of Fabricius of chicken. Chickens either die with acute infection or, if survive, become immunosu p pressed and therefore highly susceptible to other lethal diseases. Many strains have been isolated in different countries and they vary in the pathogenicity. Different strains are typed by the gene sequence of the major coat protein of the virus: VP2, which bears the neutralizing epitopes. VP2 is a polypeptide of approximated 40 kDa, which is derived from a precursor polyprotein. In this study, IBDV virus was isolated from bursae of local infected chicken collected by the Agriculture and Fisheries Department (AFD) of the Hong Kong Government, using a simplified procedure. By alignment of the gene sequences of all the published strains. oligonucleotides were designed to amplified the VP2 gene of the local strains by reverse transcriptase-polymerase chain reaction (RT-PCR). The sequences of the amplified VP2 gene indicated that two strains, including a highly virulent IBDV strain which was discovered in Japan in 1990 and an unpublished variant of IBDV, were prevalent in Hong Kong. Phylogenic tree showed that the unpublished variant is close to the highly virulent IBDV strains STC and 52/70.