Efficacy of antisepsis measures during manual milking on the prevalence of bacterial Mastitis at the Sahelian experimental station of Toukounous, Niger

Hygiene conditions during milking are essential in dairy cattle to ensure the highest level of milk production. The aim of this work was to assess the efficacy of hygiene measures during the manual milking process with no pre- or post-milking antisepsis measure at the Sahelian experimental station of Toukounous (Niger), on the prevalence of California Mastitis Test (CMT)-positive cows, on the identity of bacterial pathogens recovered from positive milk samples and on the clonality of the Staphylococcus aureus isolated. The application of mammary gland washing prior to milking, of teat dipping with chlorhexidine after milking and of milkers’ hand washing and disinfection with sodium hypochlorite significantly decreased the number of CMT-positive cows. However, the percentages of bacteriologically positive milk samples and the relative isolation rates of S. aureus and coagulase-negative staphylococci did not significantly differ according to the presence/absence of antisepsis measure. As for the clonality of the S. aureus isolates, the 53 S. aureus isolated in the absence of hygiene measures belonged to 10 pulsed field gel electrophoresis (PFGE) fingerprints, while, in comparison, only five PFGE fingerprints were identified amongst the 11 S. aureus isolated in the presence of hygiene measures. As a conclusion, the strict application of hygiene and disinfection during hand milking at Toukounous is a major contributor to the decrease of the percentage of CMT-positive cows and, therefore, of mastitis prevalence and incidence. The reasons for the persistence of the remaining S. aureus after application of hygiene measures may be numerous; one of them could be that they belong to more resistant clones.