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The most recent prospective national survey was carried out across England and Wales in 2004-05 and quantified the UK situation with regard to the pathogens involved in both clinical and sub-clinical disease (Bradley et al 2007). This work was published in the Veterinary Record, and a copy of the full paper can be requested here.

Bacteriology results obtained from 480 clinical mastitis samples submitted for culture revealed Streptococcus uberis and Escherichia coli to be the most commonly isolated organisms, accounting for 23.5% and 19.8% of cases respectively. Bacteriology results from 464 sub-clinical mastitis samples (i.e. samples from high somatic cell count cows) collected during this survey, showed 13.8% cultured S. uberis and 5.2% cultured Staphylococcus aureus although almost 40% returned a diagnosis of no growth, indicating how difficult isolation of major mastitis pathogens can be from persistently infected cases. In conclusion, the survey carried out by Bradley et al showed that environmental pathogens (pathogens predominating in the environment) tended to predominate but contagious pathogens (pathogens spreading from cow to cow) remained an important issue in some herds; a clear shift away from the UK situation 50 years ago.


More recent data published at the British Mastitis Conference in 2013 presented information regarding the aetiology (causes) of mastitis from 6,005 samples from 991 submissions to the QMMS laboratory (, coming from over 500 farms throughout the UK of which 43.8% were from clinical cases. Environmental pathogens predominated, with E. coli diagnosed in more than 19% of clinical, and 9% of subclinical submissions. Streptococcus uberis was diagnosed in 17% of clinical, and 14% of subclinical samples, whilst Staphylococcus aureus was isolated from 6% of clinical, and just over 9% of subclinical submissions. Importantly, more than 100 different bacterial species were isolated, including more unusual isolates such as Salmonella spp. and Listeria spp., making the point that the causes of bovine mastitis in the UK are extremely diverse and encompass a huge range of opportunistic environmental pathogens. Interestingly, the proportion of samples with apparent 'no growth' after 72 hours incubation was just 12% (clinical) and 10% (subclinical submissions), highlighting that well-collected samples with a detailed diagnostic approach can yield very useful information.