Page 218 - Avian Virology: Current Research and Future Trends

Infectious Bursal Disease Virus

Shijun J. Zheng 1,2,3 * 7

1 State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing, China.
2 Key Laboratory of Animal Epidemiology in the Ministry of Agriculture, China Agricultural University, Beijing, China.
3 College of Veterinary Medicine, China Agricultural University, Beijing, China.
*Correspondence: sjzheng@cau.edu.cn
https://doi.org/10.21775/9781912530106.07

Abstract 2012; Mahgoub et al., 2012). Two serotypes of IBDV are recog-
Infectious bursal disease (IBD), also called Gumboro disease, nized based on virus neutralization test (McFerran et al., 1980).
is an acute, highly contagious and immunosuppressive poultry Serotype I is the strain that targets the bursa of Fabricius (BF)
disease caused by IBD virus (IBDV). The immunosuppression lymphoid cells and can cause the clinical disease in chickens,
as a consequence of IBD increases susceptibility to other micro- while serotype II strain, primarily isolated from turkeys and
bial infections and the risk of failure in subsequent vaccinations apathogenic to poultry, does not replicate in lymphoid cells,
against other diseases. This disease still threatens the poultry but grows in chicken embryo fibroblasts (Müller et al., 2003).
industry worldwide, and in particular the frequent emergence Within serotype I group, IBDV isolates can be grouped into
of very virulence or variant IBDV strains in vaccinated flocks classical virulent (cv), hyper or very virulent (vv) and antigenic
causes severe economic losses to stakeholders. The genome variant strains. The vvIBDV strains first emerged in Europe in
of IBDV is relatively small, encoding a limited number of pro- 1980s, later was prevalent on almost all continents, causing up
teins that inhibit host antiviral response and induce apoptosis to 70% mortality in chicken flocks (Müller et al., 2003; Zorman-
in proliferating B lymphocyte in the bursa of Fabricius (BF), Rojs et al., 2003; Banda and Villegas, 2004; Xu et al., 2015).
directly breaking down the immune system of infected birds. One of the distinctive features of vvIBDV is that it can establish
The virulence factors are crucial for IBDV to avoid host defences infection in chickens with circulating antibodies against cvIBDV
and survive as a successful pathogen. Insights into the roles of serotype I. Although vaccination of chickens with appropriate
these viral proteins and cellular microRNAs (miRNAs) in host vaccines as the major and effective means of controlling IBD
response will add to the understanding of the pathogenesis of (vaccination program may vary depending on the situation of
IBDV infection and provide clues to a rational design for safer circulating virus) achieves some success, IBD is still threatening
and effective novel vaccines.This chapter focuses mainly on our the poultry industry across the globe, mostly due to the continu-
current knowledge of IBDV as an aetiological agent of IBD, the ous emergence of vvIBDV strains or antigenic variant strains that
virus–host interactions at the protein and miRNA levels during diminish the efficacy of currently used vaccines, and also due to
IBDV infection, and the control of IBD by vaccination. the virus high stability and resistance to a variety of disinfectants.
Several reviews on different aspects of IBDV were very well writ-
ten (Müller et al., 2003, 2012; Saif, 2004; Mahgoub et al., 2012;
Introduction Jackwood, 2017). Although, different types of IBDV vaccines
Infectious bursal disease (IBD), originally called Gumboro and related vaccination programs are currently available, a novel
disease, is an acute, highly contagious and immunosuppressive vaccine that can effectively control IBD is still in a tremendous
poultry disease caused by IBD virus (IBDV). The disease first demand. Elucidation of the mechanism underlying IBDV infec-
broke out in the Gumboro town of Delaware in the USA and tion may provide clues to the design of novel vaccines. In recent
was recorded as a new disease by Cosgrove in 1962 (Müller et years, much progress has been made in IBDV–host interaction,
al., 2003), and since then IBDV has worldwide distributions and the advances in the basics of IBDV pathogenesis were also
threatening the poultry industry across the globe. IBDV is a well reviewed (Ingrao et al., 2013; Qin and Zheng, 2017). The
non-enveloped and bi-segmented double-stranded (ds) RNA increasing number of publications regarding IBDV pathogenesis
virus with a diameter of about 60 nm, belonging to the genus indicates the importance of this research area and may be of
Avibirnavirus in the family Birnaviridae (Müller et al., 2003, desirable guidance to the future control of IBD.