Optimization and evaluation of 3AB3 indirect ELISA for detection of foot-and-mouth disease virus nonstructural protein antibodies in sheep.

Abstract

BACKGROUND: Foot-and-mouth disease (FMD), a highly infectious disease of cloven-hoofed animals is one of the major threats to small ruminant farming across the globe. The disease has been reported in sheep mostly co-habited with cattle in India. Implementation of effective control measures against FMD requires a multispecies approach unless a host species is proved to be epidemiologically insignificant with an appropriate diagnostic intervention. As the disease takes a mild course in sheep, clinical tissue materials from unapparent lesions are often not available. Confirmation through symptomatic diagnosis and laboratory testing of lesion tissue material is therefore hardly possible. Under such situation, serological detection of infection-specific FMD virus (FMDV) antibodies may help detecting the virus-exposed animal, subclinical or persistent infection in retrospect. METHODS: In order to demonstrate present or the scar of past infection with FMDV in animals, detection of antibody to nonstructural protein (NSP) 3AB in ELISA has been practiced in bovine population in India. The present study extended the earlier designed recombinant 3AB3 protein-based indirect ELISA originally validated on bovine serum samples to testing sheep serum samples. After optimization of the indirect ELISA parameters to test sheep serum samples, the performance was also compared with that of the internationally accredited PrioCHECK FMDV NS kit. RESULTS: The overall diagnostic sensitivity was estimated to be 92.11%, while the diagnostic specificity on naïve and vaccinated animals varied at 97.4% and 94.42%, respectively. CONCLUSION: In a country like India holding second rank in sheep population and being the largest exporter of sheep and goat meat, where FMD is prevalent and a WOAH-endorsed official FMD control programme is in place, this 'in-house' optimized r3AB3 indirect ELISA can be applied in large scale serosurveillance of FMD in sheep.