Comparative efficacy of an indigenous 'inactivated vaccine' using highly pathogenic field strain of Mycobacterium avium subspecies paratuberculosis 'Bison type' with a commercial vaccine for the control of Capri-paratuberculosis in India.

Johne's disease (JD) is endemic in goatherds located at Central Institute for Research on Goats, Makhdoom, since 1979 and lately it has been reported from farmer's herds in equal frequencies. Despite using test and slaughter method for the control of JD for more than 25 years in these herds, incidence of JD has not been reduced. Efficacy of 'indigenous vaccine' containing native 'Bison type' genotype of Mycobacterium avium subspecies paratuberculosis (MAP) was compared with commercial vaccine using challenge studies with homologous strain of MAP. Goat kids (85) were randomly divided in to three groups. Kids were vaccinated with 1 ml of vaccine subcutaneously and Sham-immunized with 1 ml of sterile PBS. All kids except 3 in each group were challenged twice at 75- and 275-day post-vaccination (DPV). Four goats each from three groups were sacrificed at 200-day post-challenge to evaluate carcass and histopathologically for vaccine and challenge response in kids of different groups. Samples (blood, serum and fecal) were screened for LTT, ELISA and shedding of bacilli and data on live animal traits, mortality and experimental sacrifice were compared. Average body weights gained by goats in three groups at different stages of trials (0, 1-75, 76-275, 276-425 DPV) showed marked improvements in performance of vaccinated groups over 'Sham-immunized' group. Effect of vaccines against challenge became visible in terms of body weights gained at 276-425 DPV ('Bison' group gained significantly higher body weights than 'Sham-immunized'). Mortality was significantly less in two vaccinated as compared to 'Sham-immunized'. Vaccinated groups also had significant stimulation and sero-conversion for cell mediated and humoral immune response, respectively as compared to 'Sham-immunized'. Results of post-challenged fecal culture showed significant reduction in shedding of MAP in both vaccinated groups than in 'Sham-immunized'. There was significant improvement in external and internal body traits and histological lesions in case of vaccinated than 'Sham-immunized' group.