Contact Transmission of Foot-and-Mouth Disease from Infected to Susceptible Cattle

Foot-and-mouth disease (FMD) was transmitted from a steer infected by intranasal inoculation of 10⁸ plaque-forming units of type O₁ FMD virus to susceptible contact steers for eight consecutive days after inoculation. The appearance of the first clinical signs of FMD in the contact steers varied from one to six days from the beginning of the 24-hr contact period with the donor. The growth of virus to the maximal infective titer was observed in the pharyngeal region of six of the eight contact steers before there was any evidence of clinical disease. Virus was found in samples of blood 1-3 days after the demonstration in the samples of pharyngeal fluid, and clinical signs of FMD always appeared within three days after the first appearance of virus in the blood.