Systematic Veterinary Virology

CULTIVATION

• Newborn mouse, chicken embryos and cell lines like African green monkey kidney (Vero), rabbit kidney (RK-13) and baby hamster kidney (BHK-21) cell lines are used for cultivation of viruses.
• In newborn mice the virus are injected intracranially. The inoculation site is just lateral to the midline into the midportion of one lateral hemisphere. Mice are observed for 10 days; dead mice are collected daily and frozen at –70°C. Mouse brains are harvested for virus identification.
• The chicken embryo is less sensitive than newborn mice. Tissue suspensions are inoculated by the yolk-sac route into 6–8-day-old embryonated chicken eggs. There are no diagnostic signs or lesions in the embryos infected with these viruses. Inoculated embryos are incubated for 7 days, but deaths usually occur between 2 and 4 days post-inoculation.
• The most commonly used cell cultures are primary chicken or duck embryo fibroblasts, continuous cell lines of African green monkey kidney (Vero), rabbit kidney (RK-13), or baby hamster kidney (BHK-21). Cultures are incubated for 7 days. EEE and WEE viruses produce a cytopathic change in cell culture. The fluid from the thawed cultures is used for virus identification.