Demonstration of antibodies against foot and mouth disease virus (FMDV) type O and Asia-1 in non-descriptive crossbred calves.

: Sera from non-descriptive crossbred calves were screened for the presence of neutralizing antibodies against FMDV type O and Asia-1 for a period up to 215 days. The antibody titer of 16 remained constant up to 215 days against type O and up to 190 days against type Asia-1 virus in some animals. In majority of the animals the antibody titers remained constant up to three months. The possible reason for a frequent breakdown of immunity in the vaccinated animals even 3-4 months after vaccination could be the fact that the calves were vaccinated repeatedly at their very early age with an ill effect of immunization in the presence of persisting antibodies.