Systematic Veterinary Virology

CULTIVATION

• The virus is easily cultivable in chickens, ECE and chicken embryo fibroblasts.
• Chickens
• This method is not recommended due to animal welfare concerns. The virus is inoculated as eyedrop.
• The virus kills the chickens 72–80 hours after inoculation. The bursae of chickens infected with virulent serotype 1 IBDV appear yellowish (sometimes haemorrhagic) and turgid, with prominent striations.
•  Peribursal oedema is sometimes present, and plugs of caseous material are occasionally found. The plicae are petechiated.
• The bursae of chickens infected with serotype 2 IBDV do not exhibit any gross lesions.
• Embryonated chicken eggs
• The virus is inoculated via yolk sac of five 6–8-day-old specific antibody negative (SAN) chicken embryos and on to the chorioallantoic membrane of five 9–11-day-old SAN chicken embryos.
• Serotype 1 IBD produces dwarfing of the embryo, subcutaneous oedema, congestion and subcutaneous or intracranial haemorrhages. The liver is usually swollen, with patchy congestion producing a mottled effect. In later deaths, the liver may be swollen and greenish, with areas of necrosis.
• The spleen is enlarged and the kidneys are swollen and congested, with a mottled effect. Serotype 2 IBDV does not induce subcutaneous oedema or haemorrhages in the infected embryos, but embryos are of a smaller size with a pale yellowish discolouration.
• Cell culture
• Chicken embryo fibroblasts are normally used for cultivation: The CPE is characterised by small round refractive cells.