Data-driven, integrated control of Streptococcus suis substantially reduces mortality and antimicrobial use in a commercial swine herd

Abstract Streptococcus suis is a major cause of meningitis, septicemia, and arthritis in swine, and its control is complicated by antimicrobial resistance and the absence of broadly protective vaccines. We evaluated a data-driven, integrated control program in a 3-year prospective, single-site quality-improvement study using an interrupted time-series design in a PRRSV-free, 1,000-sow herd comprising approximately 126,000 liveborn piglets. The program combined clinical, pathological, and bacteriological surveillance, including capsular polysaccharide ( cps ) serotyping, antimicrobial susceptibility testing with performance and antimicrobial-use monitoring. Interventions included sow vaccination with a herd-specific autogenous bacterin (serotypes 2 and 1/2), strengthened internal biosecurity, structured colostrum management supported by Brix refractometry, and antimicrobial stewardship. Data were captured using an in-house animal-health monitoring and decision-support platform. Within 6 months of program implementation, S. suis -associated mortality had markedly declined, and pathological lesions detected at necropsy decreased by approximately 50%. Within 1 year, use of Category B antimicrobials, including ceftiofur and enrofloxacin, was eliminated. By the end of year 2, metaphylactic amoxicillin use had been discontinued, and florfenicol metaphylaxis had decreased by nearly 25%. Total antimicrobial use, expressed as active antimicrobial ingredient, in suckling and weaned piglets decreased by 98.2% (from 615.8 to 11.1 kg), S. suis -associated mortality declined by approximately 90%, post-weaning mortality decreased from 2% to < 1%, and mean weaning weight increased by 10% (from 6.8 to 7.5 kg). These findings demonstrate a strong temporal association between implementation of the integrated herd-health program and substantial reductions in S. suis -associated disease and antimicrobial use, including elimination of Category B antimicrobials. Because multiple interventions were implemented concurrently and no contemporaneous control herd was available, the observed improvements cannot be attributed to any single program component.