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Mastitis Testing

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Mastitis PCR

Mastitis in dairy cows is an inflammation of the mammary gland, usually caused by bacterial infection. It’s a common and costly disease in the dairy industry, impacting milk production, cow health, and farm profitability. Mastitis can be clinical, with visible signs like swelling and abnormal milk, or subclinical, with no visible symptoms but reduced milk quality and quantity.

  • Causes:
    • Bacterial Infection: The primary cause is bacteria entering the udder through the teat canal.
    • Contagious Mastitis: Pathogens like Staphylococcus aureus and Streptococcus agalactiae can spread from cow to cow during milking.
    • Environmental Mastitis: Bacteria like Streptococcus uberis and coliforms can be found in the cow’s environment (bedding, manure) and cause infection.
    • Trauma: Physical injury to the udder can also lead to mastitis.
  • Clinical Mastitis:
    • Swelling, redness, heat, and pain in the affected quarter of the udder.
    • Abnormal milk with clots, flakes, or a watery appearance.
    • Fever, loss of appetite, and lethargy in severe cases.
  • Subclinical Mastitis:
    • No visible signs, but milk production and quality are reduced.
    • Elevated somatic cell count (SCC) in the milk.
  • Detection:
    • California Mastitis Test (CMT): A quick and easy cow side test to detect subclinical mastitis on the farm.
    • Visual and Palpation Examination: Examining the udder for swelling, redness, and heat. Examining the first few strips of milk for abnormal color, consistency, or flakes.
    • Milk Sample Analysis: Checking for abnormal milk consistency and elevated SCC.

PCR Test Options:

  • Individual Organism PCR
    • Streptococcus agalactiae, Streptococcus uberis, Prototheca, Staphyloccous aureus or Mycoplasma bovis
    • Staphylococcus aureus is one of the most common pathogens to cause chronic mastitis. It is highly contagious and usually not treatable. Infection with Staph aureus often leads to abscesses and an abundance of scar tissue in the mammary gland.
    • Mycoplasma bovis is a very small, highly contagious bacteria that can cause mastitis as well as respiratory and reproductive issues. Infection with Mycoplasma bovis is not treatable; infected cows must be identified, segregated, and culled.
  • Antelbio® STRATA-G™ Contagious 3 PCR
    • Mycoplasma bovis, Streptococcus agalactiae, Staphylococcus aureus
  • Complete 16 PCR
    • Staphylococcus aureus, Staphylococcus species, Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis, Escherichia coli, Corynebacterium bovis, Enterococcus species, Klebsiella species, Trueperella pyogenes, Serratia marcescens, Staphylococcal beta-lactamase gene, Mycoplasma bovis, Mycoplasma species, Yeast and Prototheca species.

Sample Type

  • Milk (fresh, frozen or preserved)
  • PCR detection is effective on DHI or hand-stripped milk samples from treated, fresh or late lactation cows
  • Pool samples for cost-effective screening. Split positive pools to test individual samples. Minimum of 3 samples required for pooling strategy.

When to use

  • Can be used as early as 4 days post freshening all the way to dry off

Testing Strategies

  • Convenient testing options include:
    • High SCC samples
    • Fresh cows
    • Monitor causes of infection and verify clearance before introduction
    • Bulk tank or groups to provide ongoing surveillance
  • Use the Complete 16 panel for monthly bulk tank screening. Tracking pathogens over time can help establish what is “normal” for your herd and help you quickly identify when something is “abnormal.” Further testing will be necessary when problems arise, but routine bulk tank testing can help you find those problems sooner.
  • Use the Complete 16 panel for cows with clinical or subclinical mastitis to identify the causative pathogen(s). This can be done at any time during lactation when mastitis has been detected.
  • Use the Contagious 3 panel to find cows with one of the contagious mastitis pathogens. This is ideally performed at freshening or dry off, or on newly purchased cows.
  • Use the Individual Organism assay when you only want to look for one specific pathogen – typically as verification of its previous detection.

Result Interpretation

  • Available within 48 hours of sample processing
    • Only organisms detected are indicated. If no organisms are detected, result is reported as Undetected with a Negative final result.
  • Positive results are reported as High, Moderate, or Low based on CT values. These categories indicate the concentration of mastitis pathogen that was detected.
Target Organism CentralStar PCR Test Available Ct Value Ranges Infection source, control, and keys to prevention
HIGH MODERATE LOW Undetected
Mycoplasma bovis Complete 16, Contagious 3, Single <22 22-32 32-37 >37
  • Highly contagious; spreads quickly during milking
  • Source: infected udder, respiratory tract, or urogenital tract
  • Challenges: infected cows may be asymptomatic; no effective treatment
  • Control: identification, segregation, and removal of infected animals; routine screening, especially incoming purchased animals
Mycoplasma species Complete 16 <20 20-30 30-37 >37
Staphylococcus aureus Complete 16, Contagious 3, Single <24 24-30 30-37 >37
  • Staph aureus is highly contagious and spreads easily during milking
  • Source: skin of animals and humans (all species of Staph; milk from infected cows (specifically Staph aureus)
  • Challenges: abscesses in the udder reduce antibiotic effectiveness; Beta-lactamase gene detection indicates resistance to beta-lactam antibiotics
  • Control of non-aureus Staph: broad-spectrum antibiotics
  • Control of Staph aureus: identification, sgregation, and removal of infected animals; routine screening, especially incoming purchased animals
Staphylococcus species Complete 16 <24 24-31 31-37 >37
Staphylococcal beta-lactamase gene Complete 16 <25 25-30 30-37 >37
Streptococcus agalactiae Complete 16, Contagious 3, Single <24 24-32 32-37 >37
  • Highly contagious; spreads quickly during milking
  • Source: infected udders
  • Challenges: infected cows may be asymptomatic
  • Control: identify and treat infected animals; routine screening, especially incoming purchased animals
Streptococcus uberis Complete 16, Single <21 21-31 31-37 >37
  • Environmental mastitis organisms
  • Source: manure and contaminated bedding
  • Control: maintain a clean, dry environment; follow proper milking procedures, including use of adequate pre- and post-dip products; use blanket dry cow therapy and teat sealants to cure existing infections and prevent new ones
Streptococcus dysgalactiae Complete 16 <22 22-30 30-37 >37
Enterococcus species Complete 16 <24 24-28 28-37 >37
Escherichia coli Complete 16 <24 24-34 34-37 >37
  • Environmental mastitis organisms
  • Source: contaminated bedding, manure, and improperly prepared recycled sand
  • Challenges: intramammary antibiotics are generally not recommended
  • Control: maintain clean, dry bedding; follow proper milking procedures
Klebsiella oxytoca and/or pneumoniae Complete 16 <24 24-32 32-37 >37
Prototheca species Complete 16, Single <21 21-31 31-37 >37
  • Environmental mastitis organism; can also spread from infected cows
  • Source: contaminated water sources and damp environments; infected cows
  • Challenges: no effective treatment, infections typically become chronic
  • Control: prevent cattle from accessing wet areas; maintain proper teat sanitation during intramammary teat infusions; identify and remove infected cows
Serratia marcescens Complete 16 <31 31-34 34-37 >37
  • Environmental mastitis organisms
  • Source: soil and plant matter (including feed)
  • Challenges: resistant to most antibiotics; Chlorhexidine-gluconate tea disinfectants are not effective
  • Control: implement proper milking procedures and maintain a clean and dry housing environment containing appropriate beddingmaterials
Yeast Complete 16 <22 22-32 32-37 >37
  • Environmental mastitis organisms
  • Source: contaminated intramammary infusion or damaged teat ends (e.g. hyperkeratosis)
  • Challenges: antibiotic therapy is not recommended; spontaneous cure is slow (2 months), but possible
  • Control: use clean intramammary infusion techniques; follow proper milking procedures; maintain teat health and milking equipment; remove chronically infected animals
Trueperella pyogenes and/or Peptoniphilus indolicus Complete 16 <24 24-30 30-37 >37
  • Environmental mastitis organism
  • Source: injured or damaged teats and fly contact
  • Challenges: prognosis after infection is established is poor
  • Control: implement an effective fly control program; remove infected cows
Corynebacterium bovis Complete 16 <22 22-28 28-37 >37
  • Contagious mastitis pathogen that colonizes in the teat canal; spreads easily during milking
  • Source: infected cows
  • Challenges: antibiotic therapy during lactation is not recommended
  • Control: effective post-milking disinfectants; dry cow therapy is very effective in eliminating infections

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FAQs

What is Mastitis PCR testing and why is it important for dairy herds?
Mastitis PCR testing is a fast, highly accurate method to identify the specific bacteria or pathogens causing mastitis in dairy cows. Unlike traditional cultures, PCR detects the DNA of mastitis-causing organisms, even in treated, fresh, or late-lactation cows. Early identification allows producers to target management decisions, prevent spread, and protect milk quality and production.
What types of samples are used for Mastitis PCR testing?

Fresh, frozen, or preserved milk samples can be submitted for Mastitis PCR testing.

When should Mastitis PCR testing be used?

You can use Mastitis PCR testing as early as 4 days post-freshening through dry-off. Recommended testing strategies include:

  • Monthly monitoring of bulk tank
  • Complete 16 PCR panel on high SCC or chronically infected cows to identify environmental and contagious pathogens
  • Contagious 3 panel for identifying major contagious bacteria (Mycoplasma bovis, Staphylococcus aureus, Streptococcus agalactiae) in recently fresh or purchased cows
  • Individual Organism PCR to confirm a specific pathogen previously detected
How are Mastitis PCR results interpreted?

Mastitis PCR results are available within 48 hours of sample processing. Only detected organisms are reported, providing clear, actionable data to guide herd management decisions. High Ct value = low concentration of bacteria; low Ct value = higher concentration and infection risk. Results are reported as:

  • Positive: Pathogen detected (reported as High, Moderate, or Low based on Ct values)
  • Negative/Undetected: No pathogen DNA found
What are the benefits of using CentralStar’s Mastitis PCR testing?
  • Rapid 48-hour turnaround time for actionable herd health insights
  • Accurate identification of over 16 major mastitis pathogens including Staph aureus, Strep agalactiae, Mycoplasma bovis, E. coli, and Klebsiella.
  • Cost-effective pooling options for herd-level screening
  • Supports prevention and biosecurity by identifying contagious cows before they spread infection
  • Enables data-driven mastitis control programs to improve milk quality and profitability
CentralStar’s laboratories provide sample analyses on milk, blood, fecal, and tissue samples for a variety of production, disease and health-related traits. More than 6 million samples are processed annually using state-of-the-art equipment and techniques including infrared spectroscopy, flow cytometry, ELISA, PCR, and more.

CentralStar laboratory services are intended solely for the detection of specific microorganisms or viruses in approved sample types. These services do not evaluate, certify, or guarantee the safety of milk for human consumption. It is recommended that interpretation of the results provided, and management decisions based on these results be done under the advisement of a veterinarian.