Appendix 75 Diagnostic Tools for Epidemiological Surveillance in South America Ingrid Bergmann*, Viviana Malirat, Erika Neitzert Pan American Foot-and-Mouth Disease Center (PAFMDC) Reappearance of FMDV in the FMD-free regions of the Southern-Cone of South-America 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. The 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 subregion. No evident link could be established among these isolates and lineages including viruses from the Andean subregion, reflecting two independent production systems and livestock trade circuits. Further studies were oriented to identify the source of infection. Potentially the episodes could have originated from “hot spots” within the subregion or from persistent infection in areas already declared FMD-free. In this context, serosurveillance of viral circulation through an immunoenzymatic system (screening 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 the 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 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 viral circulation shortly after the episodes, again reinforcing the observation that if carriers exist they do not play a significant role for maintenance of FMD, at least under the epidemiological circumstances of the areas studied. Based on these observations, reintroductions of FMD most probably occurred from trade activities involving “hot spots”, within the subregion.
454
