Contagious mastitis part 1: herd diagnosis

Historically much emphasis has been placed on the control of ‘contagious’ mastitis in dairy herds and the importance of preventing spread of infection between and one or more infected cows to uninfected cows in the herd, typically during the milking process. The pathogens implicated in contagious mastitis include Staphylococcus aureus, Streptococcus agalactiae and Mycoplasma spp. but ultimately all pathogens responsible for intra-mammary infection have the potential to be transmitted from one cow to another. The ability to transmit will depend on characteristics that allow them to do so (e.g. persistence in the mammary gland) and this will vary between pathogens and importantly between strains of pathogens, a good example of the latter is Streptococcus uberis. As discussed in the previous article, the analysis of somatic cell count and clinical mastitis data is essential to understand the ‘pattern’ of mastitis in a herd — and this includes patterns which would indicate that significant contagious spread may be occurring.