Staph. Aureus Mastitis


Source: Ontario Ministry of Food and Rural Affairs

Where Do They Live?

In the quarters and on the teat skin of infected cows or heifers.

How Is Infection Spread?

During milking via hands, equipment and towels used for milking preparation.


Mainly subclinical (no changes in milk or signs in cow). A few cows repeatedly have clinical flare-ups.


Culture of milk samples. California mastitis test (CMT). Somatic cell counts (SCC) on individual cows.


Reduced production.


Resistant to penicillin-type antibiotics. Most antibiotics fail to reach infected tissue and bacteria.

Estimated Cure Rates – Low

  • Antibiotic treatment during lactation – < 10%
  • Antibiotic treatment at dry-off time – < 20%

Note: Even lower cure rates can be expected for long-standing infections.

Preventative Measures:

  • Use separate paper towels for prepping each cow.
  • Dip the teats of all cows post-milking with a licensed teat dip.
  • Milk infected cows last or with a separate unit.
  • Dry treat all cows.
  • Purchase uninfected cows or heifers.