Just the tip of the iceberg…


There could be more mammary infections in your herd than meets the eye!

Early every year, there is always a terrific, “must attend” event that udder health professionals eagerly await: The National Mastitis Council’s Annual Meeting. This event never disappoints – presenting some of the highest quality, cutting edge mastitis research that the world has to offer!

One very interesting paper1 presented at the conference looked at intramammary infections over time in a Swedish dairy herd considered to have excellent udder health – a low incidence of clinical mastitis and bulk tank SCC. Specifically, the researchers wanted to study the incidence and duration of intramammary infection (IMI) of two very important mastitis pathogens – Staphylococcal and Streptococcal species in clinically healthy cows (normal milk, no inflammation, low SCC).

What they did …

Researchers visited the herd 10 times at 2-week intervals, taking quarter samples from all clinically normal animals in the herd. Samples were cultured and the duration and dynamics of infection were calculated. An average of 207 cows were sampled at each visit, resulting in over 8000 total quarter milk samples available for culture.

What they found…

Overall, 10.4% of samples were positive for either a Staphylococcal (7.5%) or Streptococcal (2.9%) species. The most prevalent pathogen isolated was Staphylococcus chromogenes, followed by Streptococcus uberis and Streptococcus dysgalactiae. Figure 1 shows the breakdown in bacterial species isolated.

The duration of each IMI also varied widely, depending on the bacteria causing the infection. Duration of infection was highest for S.uberis (56 days!) and lowest for non-chromogenes Staphylococcal species (all around 14 days) (Figure 2).

The overall rate of IMI seen in the study was ~24 infections per 100 cows per month! Previous research has estimated that an average Canadian dairy herd would see roughly 2 clinical mastitis cases (abnormal milk ± inflamed udder ± sick cow) per 100 cows per month2. That would mean that 90% or more of all infections acquired by cows are cleared by the immune system. When all is going well, that is incredible efficiency!

Pulling it all together

There are some key take-aways that this research brings to light.

Thoughts on Immunity

This study highlights a few important points on mastitis infections. There are a LOT of undetected intramammary infections that are efficiently dealt with by the cow’s immune system. These infections go unnoticed and only a few of them progress to subclinical (inflammation in the udder but no outward clinical signs) or clinical mastitis. A concerted effort should focus on preventing these infections in the first place through the 7-point plan for mastitis control. Given the ubiquity and high frequency that cows acquire IMI – even in well managed, low mastitis herds – it would seem prudent to focus on improving immune protection as another layer of defense to prevent these transient infections from becoming a problem.

Focusing on protection through optimal immunity is a necessary component of any udder health program.


As with any infectious disease, it is vital that cows are fed and consume a balanced ration to meet the needs of their physiological state (e.g. lactation, pregnancy) and support a robust and effective immune system3. Ensuring maximal dry matter intake, energy balance, as well as providing key immunomodulatory nutrients (e.g. vitamin E, selenium) will help cows fight off bacteria that gain access to the mammary gland.


There have been several technological advances in the past decade in vaccine technology and coverage. In Canada, it is possible to vaccinate cows against ~75% of the important causes of mastitis (Figure 5).

Figure 5. The top causes of clinical mastitis in Canada2. Note: Green circle denotes the pathogens that are covered by TOPVAC (S.aureus, CNS, and Coliforms) and TOP-UBAC (S.uberis).

Work with your veterinarian to design the vaccination protocol to best protect your herd. For more information on preventing mastitis, visit mastitisvaccination.com.


  1. Woudstra, S., Wente, N., Zhang, Y., Leimbach, S., & Gussmann, M. K. (2022). Incidence and Duration of Intramammary Infections with Staphylococci and Streptococci in a Dairy Cow Herd with Low Prevalence. National Mastitis Council Annual Meeting Proceedings, 204–205.
  2. Olde Riekerink, R., Barkema, H. W., Kelton, D. F., & Scholl, D. T. (2008). Incidence rate of clinical mastitis on Canadian dairy farms. J Dairy Sci, 91(4), 1366–1377. https://doi.org/10.3168/jds.2007-0757
  3. Ingvartsen, K. L., & Moyes, K. (2013). Nutrition, immune function and health of dairy cattle. Animal, 7(SUPPL.1), 112–122. https://doi.org/10.1017/S175173111200170X
  4. Bradley, A. J., Breen, J. E., Payne, B., White, V., & Green, M. J. (2015). An investigation of the efficacy of a polyvalent mastitis vaccine using different vaccination regimens under field conditions in the United Kingdom. Journal of Dairy Science, 98(3), 1706–1720. https://doi.org/10.3168/jds.2014-8332
  5. Schukken, Y. H., Bronzo, V., Locatelli, C., Pollera, C., Rota, N., Casula, A., Testa, F., Scaccabarozzi, L., March, R., Zalduendo, D., Guix, R., & Moroni, P. (2014). Efficacy of vaccination on Staphylococcus aureus and coagulase-negative staphylococci intramammary infection dynamics in 2 dairy herds. J Dairy Sci, 97(8), 5250–5264. https://doi.org/10.3168/jds.2014-8008
  6. Puig, A., Perozo, E., Roura, F., Armengol, R., Mallo, J., Echevarria, J. M., Arrieta, C., Herrera, D., Franquesa, O., Hurtado, L., Calm, I., Collado, R., Prenafeta, T., & March, R. (2018). Efficacy under field conditions of the new vaccine UBAC® in the reduction of streptococcus uberis clinical mastitis in dairy cows during a whole lactation period. National Mastitis Council Regional Meeting Milan, 318–319.
  7. Collado, R., Montbrau, C., Sitjà, M., & Prenafeta, A. (2018). Study of the efficacy of a Streptococcus uberis mastitis vaccine against an experimental intramammary infection with a heterologous strain in dairy cows. Journal of Dairy Science, 101(11), 10290–10302. https://doi.org/10.3168/jds.2018-14840