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Virginia Cooperative Extension - Knowledge for the CommonWealth

The Truth About Staph. Aureus

Dairy Pipeline: December 2007

Christina Petersson-Wolfe, Extension Dairy Scientist,
Milk Quality & Milking Management
(540) 231-4767;

Staphylococcus aureus is a contagious type of bacteria that can spread from cow to cow at the time of milking. Infected cows will have a chronically high somatic cell count many of which will be ‘millionaires’. To make matters worse, it is very difficult to get rid of these bacteria with antibiotic treatment. Therefore, we have to turn our attention to prevention.

Some basic principles of milking hygiene need to be emphasized. Gloves are crucial, and that means clean ones! Staph. aureus can colonize on our hands and wearing gloves will help stop the transmission from humans to cows. If you have a known Staph. aureus cow, change your gloves or spray them off with iodine after you prep her. This will help in preventing the spread of the bacteria from one cow to the next. Another key factor to remember is the importance of single-use towels. If we use a towel on a Staph. aureus infected cow and then use that same towel on the next cow in the parlor, we have exposed the second cow to the bacteria that is present on the cloth.

After milking, there is a residue of milk left in the unit. The next cow to be milked with that unit may be exposed to bacteria present in that residue. We do not recommend washing the units out because that can cause more harm than good. However, we do suggest the use of an approved post-milking teat dip to help prevent new infections.

Aside from milking-time hygiene, we must also remember calf management. Baby calves fed milk containing Staph. aureus can harbor those bacteria until they calve as two year olds, at which point it can show up as mastitis. Therefore, if you have identified a Staph. aureus infected cow, do not feed her colostrum to any calf. This also goes for waste milk as it can harbor all kinds of bacteria and feeding it can infect baby calves with Staph. aureus.

Our heifers are our future, so we want to ensure their health. The milk lost from an increase in somatic cell count due to Staph. aureus is tremendous. Therefore, focusing our attention on the prevention of these infections is crucial.

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