Systematic Veterinary Virology

VACCINATION

• Different vaccines have been used to control FMD for a long time.
• Frenkel method of vaccine production is a preferred method. Normal tongue epithelium was removed, minced, placed in a nutrient broth, and inoculated with FMDV. After replication of FMDV, the virus was inactivated with formalin, and aluminum hydroxide was added as an adjuvant.
• At present instead of tongue epithelium BHK21 cell line is used. These vaccines are prepared using binary-ethyleneimine (BEI) as  inactivating agent and aluminum hydroxide-saponin or oil as an adjuvant. According to prevalence of serotypes in a geographical area vaccine containing corresponding serotype(s) is used. Aluminum hydroxide vaccine offers immunity for a duration of 4-6 months after two initial vaccinations, 1-month apart and double oil emulsion vaccine offers protection for 1 year.
• Molecular-engineered vaccines are not as effective or as economical as the cell culture vaccines
• When vaccinating animals, it is important that the vaccine contain the same subtype of virus as is in the area. This necessitates frequent checking of the serotype and subtype during an outbreak because FMD virus frequently changes during natural passage through various species
• Further vaccinated animals that are not completely protected can be a source of infection. The virus may replicate and be shed, but the animals may not show any clinical sign of infection.