What types of bacteria cause mastitis?

We tend to think of there being two broad types of mastitis, based on what type of bacteria are causing the infections and where those bacteria are sourced from.

These two main types of mastitis are cow-associated (sometimes called "contagious") mastitis, and environmental mastitis.

The bacteria which cause cow-associated mastitis mostly live inside the cow's udder or on teat skin. The source of infection is other infected cows and spread of infection occurs almost exclusively in the dairy during the milking process.

The most common cow-associated bacteria found in cases of mastitis in Australia is Staph aureus.

The bacteria which cause environmental mastitis are found in many elements of the cow's environment - mud, faeces, water, etc.

Hence lanes, gateways, feed pads, leaking water troughs, etc are common sources for these bacteria to contaminate the teat surface and then enter the udder to create an infection.

Strep uberis is the most common environmental bacteria in Australian dairy herds, with E.coli being the second most common.

Whilst these are the most common mastitis causing bacteria in  Australian dairy herds, there are a number of other mastitis causing bacteria, both cow-associated & environmental which can be found in Australian dairy herds.

The importance of knowing which bacteria are causing mastitis infections in a herd is that it gives an understanding of where the bacteria are being sourced and how they are being spread; both are critical pieces of information when creating a plan to control mastitis in a herd.

Why should you get milk cultures?

Milk cultures are used to identify the bacteria associated with mastitis on a farm.

By identifying the bacteria, it provides informaton as to both the likely sources of infection, and the method by which those infections are being spread.

You could consider milk cultures to be providing a "road map" for understanding mastitis on any particular farm.

Attempting to navigate through mastitis control on a farm without an understanding of the bacteria causing mastitis on that farm is like trying to find your way somewhere without a map - there is a fair chance you will get lost!

Knowledgebase categories


General information about mastitis - what is it, what causes it, what does it cost?


How does the milking process influence the risk of mastitis?


What factors influence the risk of mastitis around calving?


How does the dry-off process influence the risk of mastitis in the dry period and at calving?


How can you minimise the effect of the environment?


When to cull, who to cull, how to choose?

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