Contribution of molecular epidemiology to improving control of Streptococcus uberis bovine mastitis

Streptococcus uberis increasingly causes intramammary infections in dairy cows through both environmental and contagious routes. In this CASDAR project, aseptic milk samples were taken every six weeks for six months from 19 herds in western France. MLVA genotyping of 703 isolates identified 203 unique strain types (5–30 per herd), allowing clear distinction between environmental and contagious epidemiological patterns. Despite its precision, routine MLVA is too expensive. Analysis of sequence variability in a single virulence gene demonstrated a lower-cost alternative that can classify mastitis schemes at the herd level (environmental, contagious, or mixed) and support targeted control measures.