Infectious Bursal Disease Virus

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Infectious Bursal Disease Virus

Characteristics of the symbiont/pathogen

The infectious bursal disease virus is a small, non-enveloped virus, that is a part of the family Birnaviridae (2). The virus has a single capsid shell made up of 32 capsomers. It has a diameter of 60 to 70 nanometers. The sequenced genome of the virus is broken down into two RNA segments. The first, larger segment is about 3,400 base pairs and the second, smaller segment is about 2,800 base pairs long (2).

Characteristics of the host

The virus causing infectious bursal disease mainly effects chicken and other avian animals. Young chicks are effected within the first six weeks of life (3). The viral disease causes necrosis of lymphocytes and specifically affects the bursa of Fabricius, a lymphoid organ (3). Chicken are the only avian species the ate susceptible to the clinical disease (4).

Negatively stained IBDV particle." [1]

Host-Symbiont Interaction

Chicken acquire the pathogenic IBD virus via oral route where it is then transported to other organs and tissue by phagocytic cells (4). Common symptoms of chickens infected with the virus include whitish or watery diarrhea, anorexia, depression, ruffled feathers, trembling, and severe prostration (3). The host and symbiont have a parasitic relationship where the virus attacks lymphoid cells and causes apoptosis of the host's surrounding cells. The host is also affected in that the virus impairs the chickens antibody- synthesizing ability to fight certain antigens (5). The interaction is facultative because the host is healthy without the virus and the virus can still survive without the host.

Infected bursa of Fabricius." [2]

Molecular Insights into the Symbiosis

IBDV is a very stable virus and and persists in poultry even after thorough cleaning and disinfecting. IBDV is also resistant to heat and ultraviolet radiation (6). There are two know serotypes of the virus. the first are more pathogenic to chicken whereas the serotype II viruses infect chicken and turkey with unknown clinical significance (3,6). IBDV RNA is consistent with a double-stranded structure and has a buoyant density of 1.62 g/ml in caesium sulphate gradients, a melting point of 95-5 °C in the presence of RNase, and a base composition reflecting the pairing of adenine and uracil as well as guanine and cytosine (6).

Ecological and Evolutionary Aspects

What is the evolutionary history of the interaction? Do particular environmental factors play a role in regulating the symbiosis?

Recent Discoveries

Describe two findings on the symbiosis published within the last two years.

References

(1)Hirai, K. and Shimakura, S. (1974). Structure of Infectious Bursal Disease Virus. Journal of Virology 14:957-964.

(2)Van den Berg, T.P. (2000). Acute infectious bursal disease in poultry: a review. Avian Pathology 29: 175–194.

(3)Wu, C.C., Rubinelli, P., Lin, T.L. (2007). Molecular detection and differentiation of infectious bursal disease virus. Avian Diseases 51: 515-526.

(4)Sharma, J.M., Kim, I., Rautenschlein, S., Yeh, H.Y. (2000). Infectious bursal disease virus of chickens: pathogenesis and immunosuppression. Development and Comparative Immunology 24: 223-235.

(5)Sharma, J.M. and Lee, L.F. (1983). Effect of infectious bursal disease on natural killer cell activity and mitogenic response of chicken lymphoid cells: role of adherent cells in cellular immune suppression. Infection and Immunity 42: 747-754.

(6)Kibenge, F.S.B., Dhillon, A.S., Russell, R.G. (1988). Biochemistry and immunology of infectious bursal disease virus. J. Gen. Virology 69:1757-1775.

Edited by Helena Shadid (Helenashadid), students of Grace Lim-Fong

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