Mastitis is an inflammation in the mammary gland caused by bacterial infection (most common) or physical trauma. In some cases, the cow's immune system (e.g. white blood cells or somatic cells) will combat and clear the mastitis much as the human body clears a common cold. Antibiotics are needed if the bacterial infection cannot be cleared by the cow. If the bacteria remain or are walled off in the mammary gland (drugs cannot reach it), it will reoccur. A good example of this is mastitis caused by Staphylococcus aureus where treatment is not very effective unless detected early. Do a keyword search in our papers section or go the the resource section and search.
Mike Hutjens, Extension Dairy Specialist, University of Illinois - Illini DairyNET
There are many factors that affect whether intramammary infections causing mastitis can be bacteriologically cured, where the bacteria are completely eliminated and most of the damage to the gland is gone. One of the most important is which bacteria are causing the infection. Many types of mastitis have high spontaneous cure rates between 70 and 94% with no treatment of any kind. Some types, however, are very difficult to truly cure no matter what antibiotic or other treatments are attempted (another example would be coliform infections). Visible mastitis such as clots or flakes may return many times from one chronic mastitis infection, but most of the time such visible signs, or even a hard quarter, go away even if the infection is not truly eliminated. Dry cow antibiotic treatment during the dry period increases the cure rate for some types of mastitis that are difficult to cure, but dry cow treatment is not always successful either. As stated above, a literature search is a good way to find out more specific information on particular causes of mastitis.
Dave Wilson, Utah State University Dairy Extension Veterinarian
