Unapparent foot and mouth disease infection (sub-clinical infections and carriers): implications for control.

Unlike animals which are carriers of foot and mouth disease (FMD), sub-clinically infected animals may be highly contagious. The implications of sub-clinical infections for the control of FMD are serious because such animals are likely to disseminate the disease when in contact with susceptible livestock. Recent dissemination of FMD virus (FMDV) in Europe shows that sub-clinically infected animals render trade in animals or animal products a potential risk for importing countries.