Antigenic variation in Foot and Mouth Disease Virus type Asia 1 isolates circulated during 1993-95 in India.

The antigenic variation in Foot and Mouth Disease Virus (FMDV) is very high. The effective strategy to control the Foot and Mouth Disease (FMD) in India which is a habitat of four serotypes O, A, C and Asia 1, is by regular vaccination, using the vaccine strain most suitable for the local situation. India is an endemic country with the disease being widely distributed. Selection of vaccine strain should therefore need the information on the circulating viruses. Asia 1 causes the second largest number of disease outbreaks in India. As there is no information available with respect to the extent of antigenic variation in FMDV type Asia 1, we have studied FMDV isolates from vaccinated and unvaccinated animals from different parts of the country and compared their relationship with Asia 1 vaccine virus. The immunogenic, hypervariable region of viral protein 1 (VP1) gene was amplified by RT-PCR and sequenced. Analysis of sequence data showed that the viruses from two field outbreaks of Southern India were closely related to each other when compared to the isolate from the North and all the three isolates are away from the vaccine virus.