Multiple-infected diagnostic specimens from foot and mouth disease endemic regions

The current routine diagnostic procedures for foot and mouth disease (FMD) virus antigen detection combine the use of an indirect sandwich enzyme-linked immunosorbent assay (ELISA) with virus isolation and amplification on cell culture. Several field samples recently received by the World Reference Laboratory for Foot and Mouth Disease which were initially diagnosed as containing a single virus type have subsequently been found to contain an additional virus type. Examples are given of the results of ELISAs performed on certain Saudia Arabian samples; these examples illustrate the problem which such multiple-infected samples present for laboratory diagnosis.