Exposure of sheep to natural aerosols of foot-and-mouth disease virus.

Sheep taken individually and allowed to inhale air being drawn along a duct from a cabinet containing pigs acutely infected with foot-and-mouth disease virus for 10 or 15 minute periods were infected by doses as low as 10 TCID50 of virus. The most consistent and reliable indicators of infection were viraemia and seroconversion. The mean times from exposure to onset of viraemia, pyrexia and the appearance of vesicular lesions were 2.5, 3.8 and 4.7 days, respectively. Neither the time from exposure to first detectable viraemia nor vesication correlated with dose. Around 27 per cent of sheep which were known to have been infected did not develop vesicles.