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Mastitis

Mastitis is one of the most significant diseases of dairy cattle.

Mastitis is an infectious disease condition resulting in an inflammatory reaction in the mammary gland of the cow. It is the most common disease in dairy cattle characterized by various degrees of severity - ranging from a mild disease with no gross changes in the secretion (milk) but an increase in inflammatory cells (somatic cells) in the milk, to a moderate disease with an increase in inflammatory cells and gross changes in the milk. It may be accompanied by signs of inflammation in the mammary gland including swelling, redness, and painfulness. Mastitis may progress to a severe disease with all of the above changes in the milk and systemic signs including fever, depression, and “off-feed” and occasionally even death in the most severe cases. Mastitis reduces milk production and milk quality.

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  • Etiology

    Mastitis causing pathogens include bacteria (mostly Staphylococcus aureus, coagulase-negative staphylococcus, Streptococcus uberis, Streptococcus dyslactiae, Streptococcus agalactiae, enterococci and coliform bacteria including Escherichia coli) and Mycoplasmas.
    Mastitis can be subdivided into two categories based on the source of infections: 1) Contagious mastitis infections acquired by transmission of contagious bacteria from cow to cow during the milking process; and, 2) Environmental infections acquired from bacteria in the environment of the cow.

  • Symptoms
    • Subclinical mastitis
      • Most commonly associated with S. aureus, Strep. Spp
      • Milk appears normal and there is no visible sign of inflammation of the mammary gland.
      • Diagnosis will be made on the basis on an increase in somatic cell counts in the milk.
    • Clinical mastitis
      • Depending on the type of pathogens involved, fever and depression could be associated with the disease.
      • Evidence of mammary gland inflammation (redness, heat, swelling, pain)
      • Physical changes in the milk (from a few milk clots to appearing like serum with clumps of fibrin).
    • Acute mastitis (organisms most commonly associated: coliform organisms including E. coli and Klebsiella, and Strep. Spp .and enterococci)
      • Most commonly associated with Coliform organisms such as E. coli and Klebsiella and with Strep Spp
      • Clinical signs (fever, depression, loss of appetite) are severe
      • The udder is swollen, hard and painful.
      • The milk may contain clots or flakes and can be watery, serous or purulent.
    • Acute gangrenous mastitis
      • Most commonly associated with S. aureus, Cl. Perfringens, and E. coli.
      • Anorexia, dehydration, depression, fever and signs of toxaemia, sometimes leading to death.
      • Early in the disease, the gland is red, swollen and warm
      • Within a few hours the teat becomes cold
      • The secretions become watery and bloody
      • The mammary gland becomes necrotic
    • Chronic mastitis (organisms most commonly associated: coagulase-negative staphylococci, S.aureus, S. uberis)
      • Most commonly associated with coagulase-negative staphylococci, S. aureus, and S. uberis.
      • Clinical signs of an acute infection from time to time with no clinical signs for prolonged intervals.
      • Milk periodically contain clots, flakes or shreds of fibrin.
      • The Somatic Cell Count is elevated.
  • Diagnosis

    Diagnosis is made on clinical signs of abnormal milk, swelling of the udder (tender to the touch) and general signs of illness (fever, depression, loss of appetite) and in many cases a reduction in milk production.


    For subclinical mastitis, the diagnosis will be made on the basis of an increase in somatic cells in the milk. Bacteriology provides useful information about the likely source of the bacteria and aids in developing a mastitis control plan.

  • Treatment
    • Dry cow intra-mammary antibiotic treatment consists of a dry tube in each quarter at dry off
    • Lactating mastitis therapy should be based upon the severity of the mastitis and knowledge of the bacteria causing the mastitis.
      • For mild to moderate cases of mastitis, the preferred route of treatment is with an intra-mammary mastitis tube
      • If cases are being treated without the results of a bacteriological culture, a tube with a broad spectrum of activity should be selected
      • If bacteriological results are known, the tube should be selected based on culture and sensitivity results
    • The antibiotics in mastitis tubes kill the bacteria that are exposed to adequate concentrations of antibiotic. Some mastitis tubes allow the use of extended therapy (up to 8 days).
    • Follow all label directions when using tubes.
    • For cows with severe clinical mastitis with systemic signs, an appropriate systemic antibiotic should be part of the therapy.
  • Prevention

    Control of mastitis is based on prevention of infections. A sound mastitis control program should implement the following practices:

    • Proper use of a functional milking machine with appropriate milking machine maintenance.
    • Teat dipping, pre- and post-milking with an effective, approved teat dip.
    • Early treatment of clinical cases.
    • Dry cow therapy at the end of lactation with one of a Dry cow mastitis products.
    • Use of an internal teat sealant.
    • Culling of cows with chronic mastitis.
    • Appropriate vaccination with a Gram-negative core antigen vaccine to prevent coliform infections.

  • Economic Impact

    Processors provide economic incentives to producers to produce and ship milk with low somatic cells. The amount of financial incentive varies from processor to processor but in many areas of the country, there are substantial economic rewards for producing high quality milk.
    An average clinical case of mastitis costs the dairy producer approximately $200. While the incidence of clinical mastitis varies greatly from herd to herd, Mastitis is one of the top three reasons producers cull dairy cows.
    In addition, Mastitis adversely affects reproductive performance of dairy cows and on average, it takes 40 days longer to get cows pregnant that have had a case of mastitis compared to herd mates that have not had a case of mastitis.
    Treatment of clinical cases of mastitis not only cost the producer in increased labor and treatment costs, and in milk discard, it also increases the risk of antibiotic residue in the bulk tank.

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