Dose-dependent responses of pigs infected with foot-and-mouth disease virus O/JPN/2010 by the intranasal and intraoral routes.

Foot-and-mouth disease virus (FMDV) infection was successfully initiated in pigs by intraoral inoculation of both 10(6) and 10(3) TCID50 of FMDV O/JPN/2010 isolated from the 2010 epidemic in Japan. By intranasal inoculation, infection was established in pigs with 10(6) TCID50 of the isolate, but not with 10(3) TCID50 of the isolate. In the pigs inoculated with 10(6) TCID50 of the isolate, viruses and viral RNAs were obtained earlier from the pigs inoculated by the intraoral route than from the pigs inoculated by the intranasal route. These results support the theory that primary infection of a pig herd is more likely to occur by ingestion than by inhalation and that the oral cavity is likely to be a major entry route for FMDV in naturally exposed pigs.