Types of Mastitis

by Mark Callow - Norco Milk Supply Field Officer Northern & Dr Bill Fulkerson - Norco Milk Supply Research & Development Officer

Not all mastitis is the same, it occurs in different forms and the physical signs of mastitis can be different. The type of mastitis in your herd depends on the bacteria causing the infection and the immune response of the cow to the bacteria.

The Countdown 2020 Farm Guideline for Mastitis Control (Dairy A u s t r a l i a p u b l i c a t i o n
http://www.dairyaustralia.com.au/Animal‐management/Mastitis/Countdown‐resources‐and‐tools‐2/Farm‐guidelines.aspx) groups mastitis into 6 forms. The worst case of mastitis is ‘severe’, the cow is very sick and can die if not treated, her udder may become gangrenous. The least invasive mastitis is ‘sub‐clinical’,
sometime this can be the most challenging to identify. A cow with
subclinical mastitis will not show any behavioural change, the udder will not be swollen or hot, her milk has no clots, and the rapid mastitis test (paddle test) may not detect any change in the consistency of solution,
but her individual cell cow will be >250,000 cfu/mL.

Different types of bacteria may cause different individual cow cell count patterns. Subclinical cases
of Staph. aureus which is a cow associated or contagious bacteria may have cell counts that rise and
fall, showing an irregular pattern during lactation. Whereas individual cell counts of cows infected with
Strep. agalactiae which is also a cow associated bacteria may be extremely high.

Stress such as a flood event, very hot days or calving may increase individual cell count levels in cows,
but the highest increases are seen in infected cows. Increased individual cow cell counts which aren’t
associated with a bacteria may occur for up to 20 days after calving.

A cow’s individual cell count can also be higher in late lactation when milk yield is low, this increases the number of bacterial cells per unit of milk. Cows in late lactation (>250 days in milk) producing 5‐7 L per day
are therefore more likely to have a higher count.

We recommended attending a Dairy Australia Cups on Cups off course run in your region.

Forms of Mastitis  Cow Udder Milk
 Severe clinical Extremely ill and depressed,
may die
May become gangrenous
(black mastitis)
May initially look normal, but soon becomes abnormal.
Acute clinical May or may not be sick Hot, swollen and painful Abnormal, may contain clots and be discoloured
Clinical No observable changes Shows little change Abnormalities are seen
Mild Clinical No observable changes Shows no abnormalities A few clots
Chronic No observable changes Lumps may be felt Mild changes, watery
Subclinical No observable changes No observable changes No observable changes, but significant increase in cell count.