Dealing With Staph. aureus Mastitis

Dr. Allen Young
USU Extension Dairy Specialist

In the past two months I have worked with or been aware of at least 6 dairies that have been struggling with the effects of mastitis caused by the Staph. aureus organism. This is a very common organism on dairies, but probably causes greater losses than any other. Some basic facts about this organism are:

1. It is considered a contagious bacterium. This means it is spread from cow to cow or human to cow through contact. This usually occurs during milking.

2. It can be found not only in the mammary gland, but also on the teats, udder and mouth of a cow.

3. Once the infection has been established in a cow, it is EXTREMELY difficult, if not impossible, to eradicate. Therefore, it is imperative that you not let this go unattended.

4. Because of the chronic nature of this organism resulting in repeated mastitis flare-ups and the very low success rate of antibiotic treatment, the control strategy should focus on prevention.

How do you know if you have this organism in your herd and what should you do if you determine that this is the cause of your problems?

1. Identify that this is the organism causing the problem. There are a couple of ways to do this. The first is to use your DHIA records. Chronically high somatic cell counts (SCC) are usually a dead give away that this organism is at least part of the problem. I suggest taking a bulk tank sample and having it analyzed for the types of organisms in the milk. You can do this by collecting a sample and sending it to any number of laboratories that can do this type of work.

2. Identify the animals that are infected. The next step is to determine which animals in the herd are infected. I would start with cows that have a chronically high SCC. Again, you can easily do this from your DHIA test or collect a composite sample from each cow and have it analyzed at a testing lab. Rocky Mountain DHIA will analyze samples even if you aren�t on DHIA. Once these high SCC cows have been identified, we have suggested taking a milk sample, or DHIA sample, and have the sample analyzed for antibodies against Staph. This is a relatively quick and simple test. Historically, Rocky Mountain has sent the samples to a laboratory in Washington that will do the test. However, this may not be an option because the lab is no longer able to get assay plates for this test. Rocky Mountain is in the process of looking for another source.

3. Determine how you are going to treat the problem. Now that you have identified the infected animals, you need to determine whether or not to treat them. Antibiotic treatment has a VERY low cure rate and you should not rely on this method to overcome the problem. However, if only one quarter is infected, you can try using antibiotics. Moderate success rates are possible. If more than one quarter is infected, the chances of antibiotic therapy working are extremely low.

4. So what can I do? The only realistic solution is to segregate infected cows from uninfected cows and milk infected cows last. This may be a real hardship on many dairies, but is necessary to break the cycle. Eventually, these infected animals should be culled from the herd when they are no longer profitable. The other major component of breaking the cycle is to have proper milking procedures. You have to have a good milking routine with proper pre- and post- dipping that is followed religiously. All milkers should wear gloves. The milking equipment should be checked to make sure it is working properly. Dry cow therapy should be used on ALL cows.

This is a problem that starts off slow and then escalates quickly. Therefore, DO NOT wait to fix the problem. Immediately work to fix it before it gets out of hand. This problem can and will cost you a lot of money if neglected. If you aren�t sure where to begin, please get some help.

For more information contact Allen Young at or (435) 797-3763. ©