Systematic Veterinary Virology

CULTIVATION

• IBV are cultivated in embryoated eggs and tracheal organ culture (TOC) system. Cell cultures are not used cultivation as it is usually necessary to adapt IBV isolates to grow in chicken embryos before cytopathic effects (CPE) of virus infection are seen in cell culture. The virus is inoculated into the allantoic cavity of 9–11-day-old embryos.
• The allantoic fluids of all eggs are pooled after harvesting 3–7 days after infection; this pool is diluted 1/5 or 1/10 in antibiotic broth and further passaged into another set of eggs. This is repeated as desired.
• A field strain will induce teratological changes in the embryo at the second or third passage consisting of stunted and curled embryos with feather dystrophy and urate deposits in the embryonic mesonephros. The allantoic fluid should not agglutinate red blood cells.
• TOCs prepared from 20-day-old embryos can be used to isolate IBV directly from field material. Tracheal rings of 0.5–1.0 mm thick are prepared using automatic tissue chopper. Infection of tracheal organ cultures produce ciliostasis within 24–48 hours.