DETECTION OF FOOT-AND-MOUTH-DISEASE VIRUS-INFECTED CATTLE BY ASSESSMENT OF ANTIBODY-RESPONSE IN OROPHARYNGEAL FLUIDS

The detection of foot-and-mouth disease virus (FMDV)-persistent carrie rs among convalescent ruminants is of paramount importance in the afte rmath of a field outbreak To this purpose, FMDV-specific antibody shou ld be investigated first, since virus isolation procedures from such c arriers are seriously constrained. The complexity of the overall pictu re may be compounded by possible emergency vaccinations in the affecte d areas at the beginning of the outbreak. In this case, it is suggeste d that mucosal rather than serum antibody be investigated. In fact, we showed that FMDV-infected cattle regularly mount an antibody response in oropharyngeal fluids, in contrast to vaccinated cattle. Antibody c ould be revealed by neutralization assays and/or an immunoglobulin A ( IgA)-specific kinetic enzyme-linked immunosorbent assay (ELISA). Cattl e vaccinated once seldom showed a mucosal antibody response, which cou ld be only detected by a total immunoglobulin-specific kinetic ELISA. Very few, if any, cattle showed a mucosal IgA response after repeated vaccinations. Our kinetic, IgA-specific ELISA generally allowed an ear ly detection of FMDV-infected cattle; in particular, it proved to be m ore sensitive than the usual indirect, antigen-trapping ELISA in exper iments on saliva samples.