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What is FMD? |
Agent responsible |
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Antigenic characteristics of FMD |
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FMD virus is antigenically heterogeneous. Seven serotypes are recognised, O, A, C, SAT1, SAT2, SAT3, ASIA1 (SAT = Southern African Territories). The serotypes of FMD virus were originally identified by cross-immunity experiments in animals. An animal recovered from infection with one serotype being resistant to challenge by the same serotype but remaining susceptible to infection by any other serotype. Each serotype of FMD is antigenically distinct from the other six serotypes. Furthermore, within each serotype, there is considerable antigenic diversity. For this reason, antisera raised to one strain of a serotype may not recognise other strains of the same serotype. This is particularly true for type A. Historically, isolates were classified into antigenically related 'sub-types' within a serotype, e.g., 01, A22, A24, C1. This classification has now largely been superseded and strains are classified according to their antigenic similarity to well-known vaccine strains. |
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