Experiments with a Modified Strain of the Virus of Foot-and-mouth Disease

Abstract

SUMMARY A cattle strain of the virus of foot-and-mouth disease of type S.A.T.2, modified by serial passage in mice and eggs, has been shown to be sufficiently reduced in pathogenicity to warrant its use as a live virus vaccine in cattle. Eighteen of 275 cattle developed lesions on one or more feet when inoculated by various routes with different samples of the modified strain. The protection afforded against challenge with unmodified virus was greatest when the cattle were vaccinated by the intradermal tongue route. Of 49 cattle in one series of experiments, 36 were completely protected and a further 5 partially protected against challenge. Vaccination by intra-muscular, subcutaneous and intracutaneous routes protected 19 out of 33 animals and partially protected a further 6. In an experiment in East Africa, 18 of 22 grade cattle were completely protected and a further 3 were partially protected.