Equine influenza (EI) is a highly contagious self-limiting respiratory disease in horses that is caused by equine influenza virus (EIV) infection. EIV is presented by horses worldwide and has a huge financial impact on the horse industry in many countries. Although an outbreak of EI can be controlled by prior immunization by using vaccination, the efficacy of the vaccine is influenced by antigenic differences between epidemic strains and vaccine strains. Thus, to keep the vaccine effective, the vaccine strains should be reviewed periodically on the basis of global surveillance, such as the epidemiological report issued annually in the bulletin of the World Organization for Animal Health. Once an outbreak occurs, sanitary management, including the restriction of horse movement, should be conducted to eliminate the source of the causative virus and protect susceptible horses. The rapid identification of EIV in respiratory tract secretions enables the prompt administration of sanitary management. Although commercially available rapid antigen detection tests should be improved in terms of sensitivity, one of the tests (ESPLINE Flu A+B) worked as a convenient method for the rapid diagnosis and screening of a number of horses for EI during the 2007 outbreak in Japan, in addition to laboratory tests such as virus isolation. A more sensitive test must be developed that can be performed easily without special equipment or technical expertise.
