Method for determining a degree of infection

A method for determining a degree of infection comprising the steps of

• i) preparing an un-isolated sample by adding a reagent comprising a differentiating marker in an amount sufficient to provide a differentiation between cell types to mammalian milk in a dilution ration of less than 1:200, preferably leas than 1:50 and most preferably less than 1:5;
• ii) measuring a cell count for each of one or more types of somatic cell differentiated by the marker on the sample by means of a flow cytometer having a detection system sensitive to differences in the differentiating marker resulting from the marker becoming differently associated with different cell types in the sample;
• and
• iii) determining an indication of a degree of infection dependent on the measured cell count.