A Field Trial in South Africa of an Attenuated Vaccine Against Foot-and-Mouth Disease

Abstract

SUMMARY In a field trial, mouse adapted foot-and-mouth disease virus of type SAT 2 was relatively non-pathogenic for cattle when given intramuscularly. Mild lesions were seen in only 0·35% of over 3,400 animals vaccinated. No abortions or deaths attributable to the vaccine were noted, although all ages and sexes were vaccinated. The virus did not appear to spread to unvaccinated control cattle. When challenged by the intramuscular injection of a heterologous strain of the same type of virus, about 70% of the vaccinated adult cattle were found to be completely protected, whereas almost 97% of controls developed lesions. The immune response in calves was difficult to assess because a high percentage of the control calves did not develop lesions after the challenge infection.