Staphylococcus aureus Mastitis: Cause, Detection, and Control

Control measures aimed at preventing S. aureus from entering the teat canal, namely milking time hygiene, has reduced the prevalence of this disease on many modern farms, yet the disease is still prevalent .

Staphylococcus aureus causes one of the most common types of chronic mastitis. Though some cows may flare up with clinical mastitis (especially after calving), the infection is usually subclinical, causing elevated somatic cell counts (SCC) but no detectable changes in milk or the udder

S. aureus bacteria produce toxins that destroy cell membranes and can directly damage milk-producing tissue. White blood cells (leukocytes) are attracted to the area of inflammation where they attempt to fight the infection.

The major reservoirs of S. aureus are infected udders, teat canals, and teat lesions, but these bacteria also have been found on teat skin, muzzles, and nostrils. The bacteria are spread to uninfected quarters by teat cup liners, milkers’ hands, washcloths, and flies

1. Milkers should always wear gloves and change them frequently, especially when dirty or after stripping an infected animal. It is recommended to fore strip five squirts of milk from each quarter and check for abnormal milk or flakes.
2. Dirt should be brushed off teats with the use of a dry, single-use towel. Water should not be used as part of any milking procedures, even if a sanitizing solution is added. Sanitizers do not maintain activity throughout a milking, and water can introduce pathogens that are very difficult to cure.
A commercially available pre-dip should be applied with a dipper or cup and given 30 seconds of contact time. Sprayers can be used, but proper coverage is difficult to attain, especially on the teats farthest from the milker. Foamers are also commonly used, but caution must be taken to ensure that adequate parts per million of the active ingredient reach the teat end and teat skin.
3. A separate paper or cloth towel should be used to dry teats and scrub teats five times or for 20 seconds (Rasmussen et al., 1992). Towels must not be used on more than one cow.
4. Milking units should be attached 90 seconds after first tactile stimulation (stripping or wiping, whichever comes first).
5. Teat ends should be examined for evidence of chapping, cracks, or lesions, which may harbour mastitis-causing bacteria.
6. An effective post-milking teat dip should be applied after milking, ensuring that the entire barrel of each teat is covered. At the end of each milking, any teat dip left in the dip cup should be discarded, and cups should be rinsed with water and allowed to dry.
It is important to educate your employees.

Antibiotic treatment will not control this disease, but it may, in certain cases, shorten the duration of the infection. Treatment effectiveness decreases as the cow becomes older and even as the first lactation progresses

Dry cow therapy is more effective in eliminating infections than lactating treatment.

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