Latent viral infection in transmission of foot-ana-mouth disease by contact between infected and susceptible cattle.

Abstract

An experiment on the transmission of foot-and-mouth disease (FMD) from infected to susceptible cattle showed that the disease may occur in a form that has not been previously described. A steer inoculated intranasally with FMD virus remained clinically normal but transmitted the disease to a series of susceptible contact steers for at least eight days. The incubation period in the contact steers varied from 40 to 120 days, even though FMD virus was isolated from the blood of several steers shortly after contact with the donor steer. The prolonged absence of disease or development of antibody, and the frequent isolation of bovine enterovirus from samples of serum and esophageal-pharyngeal fluid led to the postulation of phenotypic encapsidation of FMD virus RNA by the coat protein of bovine enterovirus in the donor and contact steers. The procedures required for isolation in tissue cultures of FMD virus from samples of serum supported this hypothesis.