Staph. aureus
A worldwide emerging contagious mastitis pathogen. Staph. aureus is of high interest as it is mainly subclinical and without control may result in long term persistent infections, high bulk tank SCC, lost quarters or culls.
UnderstandingStaph. aureus mastitis
A common cause of mastitis. Often silent—but not harmless. Staphylococcus aureus is one of the most persistent and contagious mastitis pathogens in dairy herds. It hides in plain sight, spreads easily during milking, and is notoriously difficult to cure once established. But with the right approach, it can be managed
Staph. aureus is a bacterium found on the skin, in nasal passages, and on the hands of both cows and people. It spreads mainly during milking—through liners, hands, and milk droplets—and cows may be exposed or infected at any point during lactation or the dry period.
Once inside the udder, it can settle deep in the tissue and cause chronic, low-grade infections. These cows may appear healthy, but they continue to shed bacteria and infect others.
“Most herds will have some cows with Staph. aureus infections. With good management, these bacteria have minimal impact. But if not well managed, infections may spread from cow to cow.” — DairyNZ, 2022
Staph. aureus bacteria as seen under a microscope at 100× magnification
Via teat cups, liners, and milk droplets.
From cross-suckling or shared equipment.
When infected animals are purchased.
Around 30% of people are carriers; bare hands are a known risk; gloves matter.
What it means for your herd
Key consequences for herd performance and health
What you can do
Controlling Staph. aureus requires more than treating clinical cases or testing high SCC cows. Effective prevention relies on stopping bacteria from spreading between cows.
Here are essential strategies for control that work:
Monitor Staph. aureus in your bulk tank using a diagnostic test like Snapshot®
Milk high-SCC or infected cows last to prevent spread
Use teat spray with full coverage after every milking
Avoid overmilking and check machine settings to reduce teat end damage
Test suspect cows. Use inline conductivity testing or herd testing and follow up with culture diagnostic testing like Fresh Cow Dry Cow® for pathogen identification
Wear gloves during all milking and cow handling
Test new cows before introducing them to the herd
Why it’s often missed
Subclinical infections dominate – up to 95% of infected cows may show no visible signs.
SCC alone isn’t reliable – infected cows can have low SCC and still spread the pathogen.
Misidentification is common – especially when using low sensitivity technologies or non-aseptic sampling.
Herdscreen® identifies Staph. aureus down to 165 cfu/mL and distinguishes it from other pathogens, allowing you to act with confidence.
Managing infected cows
Treatment should be guided by vet consultation and herd priorities. A single positive result isn’t always a reason to cull—but chronic carriers must be managed carefully.
Effective control measures-
Always segregate infected cows and milk them last.
Never feed waste milk from infected cows to calves.
- Dry cow antibiotic therapy (DCAT) at dry off. (Consult your Veterinarian)
- Early dry-off or drying off an infected quarter.
- Selective culling after repeated infections.
We’ve put together the most common questions dairy farmers have about Staph. aureus
Staph. aureus mastitis is a contagious udder infection caused by the bacterium Staphylococcus aureus. It spreads mainly during milking and often becomes chronic. Infected cows may produce lower-quality milk and show increased somatic cell counts (SCC).
Yes. Typical cure rates range from 25–50%, and they drop even further for chronic infections. Once the bacteria settle deep in the udder tissue, they are difficult to eliminate—even with dry cow therapy.
Yes. Many infections are subclinical. These cows may have low SCC but still carry and spread the pathogen, so diagnostic testing is essential.
Tools & next steps
Herdscreen®
Use Herdscreen® to detect all infected animals in case of high impact of staph. aureus in the herd to reset. —even cows with low SCC
Fresh Cow Dry Cow®
Use Fresh Cow Dry Cow (FCDC) on-farm testing early for all suspect cows – High SCC and cows new to the herd
Bovine Mastitis Cure Calculator
Shows which mastitis cases are likely to respond to treatment.
Best hygiene practices
Review your milking routine and team hygiene practices.
Manage Staph. aureus with confidence
Because early action and the right support make all the difference.
