Vaccination: foot-and-mouth disease experience in South America

Abstract

Vaccination against foot-and-mouth disease (FMD) constitutes an important component of the policy for its control and eradication in South America. Considering that immunization may not impair subclinical infection, it became advisable to ally to vaccination campaigns a surveillance instrument to monitor silent viral circulation. Novel approaches for the evaluation of antibodies to FMD non-capsid proteins (NCPs), developed and validated at PANAFTOSA proved valuable for assessing viral circulation in immunized populations. The extensive and coordinated application in South America of vaccination together with this serosurvey tool indicated the effectiveness of systematic vaccination to prevent FMD spread and to restrain silent viral circulation intra- and inter- herds, and gave input to an old controversy related to the real epidemiological significance, if any, of carrier animals under the vaccination conditions in South America. The fitness of NCP tests to assess viral circulation in a population supported the incorporation into the OIE code of the "free of FMD with vaccination" category as a step prior to the recognition of the "free of FMD without vaccination" category. Likewise it released the path to allow animals, vaccinated for protective purposes during emergencies, to live for the term of their productive lives.