Background: Brucella abortus S19 vaccination forms the cornerstone of the national brucellosis control program. Monitoring post-vaccination immune responses is crucial to assess vaccine performance across diverse regions and species. Methods: Two-phase nationwide seromonitoring study was conducted during 2021–2022 (Phase I) and 2022–2023 (Phase II) across seven geographical regions. A total of 51,759 serum samples were collected from S19-vaccinated cattle and buffalo calves of 4–8 months at four-days post-vaccination (DPV) intervals. Samples were analyzed using an in-house developed protein G-based indirect ELISA, and seroconversion rates were calculated. Statistical comparisons were performed, and spatial heterogeneity was mapped. Results: The overall seroconversion rate was 70.96%, with Phase I showing a higher seropositivity (76.05%) than Phase II (65.66%). Regionally, the Western (81.8%) and Southern (80.77%) regions showed the highest efficacy, while the Central region had the lowest (65.89%). Antibody kinetics peaked at 21–45 DPV (73.14%) and declined gradually to 43.27% by 91–120 DPV. A clear species effect was observed, with cattle calves showing higher seroconversion rates (77.12%) than buffalo calves (67.34%). Conclusions: This large-scale systematic evaluation highlights that S19 vaccine induces substantial seroconversion with regional, temporal, and species-specific differences. These insights provide crucial evidence for refining and strengthening India’s national brucellosis control program.

A comparative cross-sectional study was undertaken in organized and unorganized dairy sectors to evaluate the prevalence of bovine mastitis and the antibiotic resistance in Staphylococcus spp. of dairy animals and their associated personnel. A total of 391 households (HH) consisting of 211 and 180 HHs from organized and unorganized sectors, respectively, were selected based on 30-cluster sampling methodology in southern and northeastern regions of India. From 391 HHs, a total of 1920 milking cows (organized dairy—533; unorganized dairy—1387) were screened for subclinical and clinical mastitis by the California Mastitis Test (CMT). Out of 1920 milk samples, 1002 milk samples, 362 associated personnel hand and nasal swabs, and 27 milking machine swabs were sourced. The samples were subjected to Staphylococcus spp. by isolation and identification by multiplex polymerase chain reactions (mPCRs) and antibiotic sensitivity testing (ABST) to determine antimicrobial resistance (AMR) profiles. CMT results showed high mastitis prevalence (54.65%) in unorganized farms compared to organized ones (45.78%), with a significant association of mastitis to dairy sectors (p = 0.0004). On speciation, S. aureus isolates were comparatively less than those of coagulase-negative staphylococci (CoNS) (3.5% and 7.7%, respectively) in the organized dairy sector, and the same was recorded for the unorganized dairy sector (0.85% and 13.19%, respectively). In both the dairy sectors, the highest antibiotic resistance for Staphylococcus spp. was observed against the β-lactams (penicillins and cephalosporins) group (71.36% and 76.59%) and the lowest for nitrofurans (3.5% and 3%), oxazolidines (0.7% and 5.1%), and rifamycin (0.7% and 5.1%), respectively. In both the sectors, human isolates had comparatively high mecA positives (15.70% and 15.96%) compared to the animal isolates (8.36% and 12.94%). Based on mPCR, a smaller number of methicillin-resistant S. aureus (MRSA) isolates (3.95%) than methicillin-resistant coagulase-negative Staphylococci (MRCoNS) was detected in milk samples (6.05%), and the same was observed for associated personnel samples (MRCoNS (14.63%) compared to MRSA (1.05%)). In four HHs, mecA positives were detected in both animal and human samples, and this highlights the transmission dynamics of mecA between animals and humans in households. The resistance of Staphylococcus spp. to β-lactams highlights the need for cautious antibiotic use to prevent AMR.

Background: Human brucellosis is a major occupational hazard in India, especially among veterinary healthcare workers due to frequent contact with livestock. This study evaluated in-house standardized IgM and IgG-based lateral flow assays (LFAs) against a Rose Bengal Plate Test (RBPT) and a Serum Agglutination Test (SAT). Methods: A total of 1356 serum samples (392 veterinary doctors and 964 paraveterinary staff) were sourced for evaluation of the tests across Karnataka, India. The results were analyzed for performance metrics {DSe (Diagnostic Sensitivity), DSp (Diagnostic Specificity), PPV (Positive Predictive Value), NPV (Negative Predictive Value), accuracy, and kappa with 95% CI} through chi-square and regression analyses. Results: Overall seropositivity was 7.67% (104/1356; 95% CI: 6.31–9.22) by RBPT, 3.47% (47/1356; 95% CI: 2.56–4.58) by SAT, 2.95% (40/1356; 95% CI: 2.12–4.00) by IgM_LFA, and 6.34% (86/1356; 95% CI: 5.10–7.77) by IgG_LFA. The RBPT vs. IgM and IgG_LFA showed a DSe of 85.3% (74.6–92.7) and 82.69% (74.03–89.41), respectively. Compared with SAT, IgM_LFA and IgG_LFA demonstrated high DSe values of 95.35% (84.2–99.4) and 96.55% (88.1–99.6), respectively. Seroprevalence was higher among paraveterinary staff (8.71%, CI 95%: 7.20–10.90) than veterinary doctors (5.10%, CI 95%: 3.14–7.77), higher in males (8.30%, CI 95%: 6.77–10.04) than females (4.02%, CI 95%: 2.44–9.05) and higher in individuals aged >55 years (9.09%, CI 95%: 5.64–13.69) compared to other age groups. Regression analysis yielded coefficients of 62.90% (p = 0.0107) for veterinarians and 87.89% (p = 0.0001) for paraveterinarians. Conclusions: This integrated field evaluation confirms improvement in brucellosis detection and emphasizes the need for field-applicable diagnostic tools.