Foot-and-mouth disease: reaction of convalescente pigs to homologous virus exposure

Abstract

Pigs are more difficult to protect against foot-and-mouth disease (FMD) with inactivated virus vaccines than cattle or sheep (4, 6, 7). Also the results of exposure of convalescent pigs to homologous FMD virus have been variable. Cunliffe (2) studied the antibody level of FMD convalescent pigs and re-exposed them to the homologous virus 28 days or 128 days after the initial infection, respectively. Only one of 10 pigs of the last group became clinically ill at re=exposure. How-ever, McKercher and Giordano (8) reported that at re-exposure, from 12 convalescent pigs (90-180 days after infection), 6 showed lesions on the snout or on one or more feet. These authors used contact exposure with FMD-infected pigs as a mean of re-exposure, since this method was considered the one by which pigs would naturally be infected.