Use of PCR testing for Foot-and-Mouth Disease under emergency conditions

MALIRAT V.; BERGMANN, I.E.

Viña del Mar, Chile

Simposio; 10 Simposio Internacional de Epidemiología y Economía Veterinaria, ISVEE 10,; 2003

International Society for Veterinary Epidemiology and Economics

Identification of animals infected with foot-and-mouth disease virus (FMDV), either clinically or subclinically infected, during a sanitary emergency should be particularly sensitive in those areas with advanced eradication programs. In this regard, development and validation of rapid and precise methods for detection and viral characterization becomes essential within the Hemispheric Program for the Eradication of Foot-and-Mouth Disease (PHEFA) The Polymerase Chain Reaction method (PCR) was evaluated for its potential use for identification of the agent during emergencies, as well as for its fast `typing`. Four primer pairs were selected. One of them directed to a more conserved region of the viral genome, which corresponds to the polymerase 3D coding region, in order to identify the virus, regardless of the serotype. The other three pairs, flanked the region that codes for the VP1protein, thus corresponding to type-specific regions defined for each one of the three serotypes registered in South America (O, A and C). This selection would permit the discrimination of the serotype involved. During the validation process, the RNAs obtained from more than 100 viral strains representing outbreaks registered  between 1945 and 2002, encompassing the 3 serotypes and epidemiologically relevant for the region, were evaluated. Whenever possible, comparisons were done among amplifications obtained directly from epithelium samples, from esophageal-pharyngeal fluids, or after passages in cell cultures. The results obtained showed the effectiveness of the RT-PCR method not only to detect with high sensitivity and in few hours, FMD viral sequences, but also for the identification of the viral type involved, aiding in the diagnosis of foot-and-mouth disease, particularly for field situations where a rapid response is requested, like those in which effective eradication programs are in progress.