Diagnostic tools for epidemiological surveillance in South America

BERGMANN, I.E.; MALIRAT V.; NEITZERT E.

Chania, Creta, Grecia

Otro; Session of the Research Group of the Standing Technical Committee of the European Commission for the Control of Foot-and-Mouth Disease (EUFMD),; 2004

European Commission for the Control of Foot-and-Mouth Disease (EUFMD)/FAO

Reappearence of FMDV in the FMD-free regions of the Southern Cone of SouthAmerica in 2000-2001 prompted the need to understand the putative origin of these emergencies. Thus efforts were oriented to identify genetic links among strains through the constitution of a genetic database by the PAFMDC, including viruses recorded in endemic regions and during the emergencies. Thew phylogenetic analysis placed all emergency isolates in a single lineage together with viruses previously circulating in the  Southern Cone, or currently appearing in high-risk zones with sporadic disease (“hot-spots”) of this sub-region. No evident link could be established among these isolates and lineages including viruses from the Andean subregion, reflecting two independent production systems and livestock circuits. Further studies were oriented to identify the source of infection. Potentially the episodes could have originated from “hot-spots” within the sub-region or from persistent infection in areas already declared FMD-free. In this context serosurveillance of viral circulation through an immunoenzymatic system (screening I-ELISA 3ABC and confirmatory EITB) developed and validated at PAFMDC constituted an important adjunct , particularly using the criteria for assessing risk of viral circulation in a population (age stratification, graphic displays, multifactorial analysis, etc), identified after its extensive use in SouthAmerica. Follow-up of serosurveys in the Southern Cone during advanced stages of eradication programs strongly indicated clearance of viral circulation shortly after last episodes. This was reinforced by the lack of outbreaks in these areas even for many years after suspension of vaccination, indicating that reappearance of the disease was not due to a carrier capable of causing an episode. Moreover, the use of this system in longitudinal studies to follow up viral activity after emergencies demonstrated clearance of  of viral circulation shortly after the episodes, again reinforcing the observation that if carriers exist they do not play a significant role fort maintenance of FMD, at least under the epidemiological circumstances of the areas studied. Based on these observations reintroduction of FMD most probably occurred from trade activities involving “hot-spots”, within the subregion