Detection of anti Non-Structural protein 3A (NSP-3A) antibodies in sera of cattle and buffaloes vaccinated with FMD vaccine in Haryana
Abstract
Foot-and-mouth disease (FMD) is a highly infectious and contagious vesicular disease affecting cloven-hoofed animals. FMD virus (FMDV) belongs to the genus Aphthovirus in the Picornaviridae family and includes seven serotypes, O, A, Asia1, C, and SAT1, -2, and -3. The circulation of FMDV in an animal population imposes severe restrictions on the movement of animal products and consequently on international trade. FMD is endemic in many parts of Asia, Africa, and South America.
In India, mass vaccination with trivalent vaccine (O, A, and Asia1) has been adopted for control and eradication for FMD. Due to endemicity of the disease, FMD control programme has been launched in selected states including Haryana to create FMD free zones. The major constrain to attain the FMD free status is the carrier animals. A carrier of FMDV is defined as an animal from which live-virus can be recovered from scrapings of the oropharynx after 28 days following infection (Sutmoller and Gaggero, 1965).
FMD vaccines do not provide sterile immunity and animals can become clinically or sub clinically infected and ultimately become carriers of the virus, which is considered a threat for spread of the disease to other susceptible animals (Cox et al., 2005, 2006; Doel et al., 1994; Hargreaves et al., 2004; Kitching, 2002; Moonen and Schrijver, 2000). Therefore, to regain FMD-free status and re-enable international trade, post vaccination surveillance is required to demonstrate the absence of persistent infection in a vaccinated population (Anon. 2004).
In the present study, a total of 2000 serum samples were used in Liquid phase blocking ELISA (LPBE) for vaccinal antibody response and 3A-NSP ELISA for carrier/persistent infection of the FMDV. On analyzing those serum samples for vaccinal immune response using LPBE, it was observed that there was no significant difference in FMD-CP (FMD-control programme) districts and ASCAD (Assistance to States for Control of Animal Diseases programme) districts of Haryana irrespective of biannual and annual vaccinations respectively. Also same serum samples were used for detection of antibodies to 3A-NSP where it was
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observed that there was no significant difference in prevalence of anti-3A NSP antibodies in serum samples of cattle and buffaloes taken together from FMD-CP and ASCAD districts of Haryana. It was found that anti-3A NSP antibodies positive cattle were significantly higher than buffaloes (p<0.001) in both the FMD-CP and ASCAD districts. Further isotyping of 3A-NSP specific antibodies to know which isotype of immunoglobulin IgG predominated during the FMDV infection revealed that both isotypes i.e. IgG1 and IgG2 were prevalent in both the FMD-CP and ASCAD districts.