Non-structural protein 3A for differentiation of foot-and-mouth disease infected and vaccinated animals in Haryana (India).

There are severe international trade restrictions on foot-and-mouth disease (FMD) affected areas. Because of endemic nature of FMD, India started FMD control programme (FMD-CP) using mass vaccination in selected states including Haryana (year 2003). Although no significant incidence of the disease was reported after launching FMD-CP in the state but in order to participate in international trade of animal and animal products, veterinary authorities have to prove that there is no FMD virus (FMDV) circulation in the animal population, for which it is necessary to differentiate the FMD infected and vaccinated animals. For this purpose, an in-house indirect ELISA utilizing baculovirus-expressed FMDV non-structural protein (NSP) 3A was used to find evidence for virus circulation (prevalence of anti-NSP 3A-specific antibodies) by examining serum samples that were collected either before start of FMD-CP or after completion of third phase (Pre-4th) of vaccination in Haryana (India). A significant reduction (P < 0.01) in prevalence of anti-NSP 3A-specific antibodies (possibly carriers) was observed 2 years after launching FMD-CP in Haryana. However, in cattle the percentage of animals with anti-NSP 3A-specific antibodies was found to be significantly higher (P < 0.01) than buffalo, both before (P < 0.01) and after (P < 0.01) launching FMD-CP in the state. The findings of this study suggest that use of FMDV vaccine in cattle and buffaloes in endemic areas reduces virus circulation (carriers) in the vaccinated herds and that the current 3ANSP-ELISA can be successfully used to monitor the FMDV circulation in endemic areas.