Dr. Andrew P. Johnson
W 8275 Cloverleaf Lake Road
Clintonville, Wisconsin 54929
Phone: 715-823-7933 Fax: 715-823-7880 Cell: 920-621-3604


Mycoplasma is a contagious organism that can cause mastitis in cattle. The animals DO NOT get sick, the mastitis is not responsive to medications, and the infection will usually spread from quarter to quarter. It is rare for animals to get sick and die unless they have the respiratory form of Mycoplasma.

On many first time herds, the source of Mycoplasma is purchased cattle especially springing heifers. These animals are usually trucked for a long distance. The Mycoplasma usually starts with respiratory disease. The respiratory disease puts animals at risk to mastitis if the teats are exposed to nasal discharge or aerosol contamination.

It is critical that fresh animals (unusable milk) and hospital cows are NEVER mixed in the same pen. If these animals are mixed together, the risk of Mycoplasma spread is greatly increased. Fresh animals are the most susceptible animals to new diseases and are greatly at risk to picking up contagious diseases if mixed with hospital cows. This is a common mistake of many dairies.

When first positive bulk culture is received, don't panic. The first thing to do is resample the bulk tank and make sure your herd is really positive. There is always a chance samples were mixed up or improperly labeled.

If the next bulk tank culture is positive, then you should take some action to determine which cows are infected. I would suggest doing string or pen samples first to see if you can find the group of cows to culture. It is important that no cows be moved from pen to pen until the string or pen cultures are back from the laboratory.

All cows in the positive pens or strings need to be cultured. These cows cannot be moved until the results are back from the laboratory. All positive animals need to be isolated and evaluated animal by animal. All culture positive animals DO NOT need to be sold. Because Mycoplasma sheds in extremely high numbers, it is not uncommon for cultures to be positive from negative cows. If the cows have abnormal milk or high CMT, they should be sold. If the animals have normal milk, no clinical mastitis and a normal CMT, they need to be cultured again. These questionable animals need to be leg banded and should be milked last. At the very least, after these animals are milked the inside and outside of the milking claw must be sanitized before another cow is milked. If the second culture is negative and the milk is still normal with a negative CMT, the cows can be considered normal.

When large numbers of animals are infected, you may need to develop a Mycoplasma group and cull these animals slowly over time. It is important to consider the economics of the dairy before culling all animals.

All dairies that have a positive Mycoplasma problem must culture all fresh animals after calving. Positive animals must be isolated and evaluated individually. No animal can leave the fresh group until the culture results are known or you run the risk of infecting a group of clean animals. All clinical cases MUST be cultured for Mycoplasma. If they culture positive, they must be culled. Never move cows out of hospital barn without a negative culture.

Another key to the prevention of Mycoplasma in a dairy herd is to set up an effective treatment protocol. In some situations, dairies are better off to stop all intramammary therapy in order to stop the spread of Mycoplasma in the hospital barn. If the dairy is going to treat infected quarters during an outbreak of Mycoplasma, they need to put on a new pair of gloves for each cow. Only single use treatment applications are allowed. A common way to spread Mycoplasma in a dairy is multiple use treatment containers such as home made treatments or extra label treatments. Multiple use containers of medication are absolutely forbidden in the intramammary treatment of mastitis. After milking each cow, the unit must be sanitized both on the inside and outside. Hands are a key source of spread when working with the infected cows. If the milkers are not following a very strict treatment protocol on all animals in the hospital barn, the hospital barn becomes Mycoplasma City.

With the right management practices and lots of hard work, Mycoplasma can be effectively controlled or even eradicated in less than 3 months. The secret is to stop new cases from occurring in the dairy. Once the new cases have stopped, the disease can be eliminated quickly. The herd will need to have monthly bulk tank cultures for at least one year and should continue to culture all clinical, all purchased animals and all fresh animals for at least six months after a negative bulk tank culture.

Remember with Mycoplasma in your herd, you don't have to panic. If you are using good effective mastitis control practices on your dairy when Mycoplasma enters the herd, the risk of spread is very minimal. Unfortunately, if you are not implementing good mastitis control practices, Mycoplasma can spread very rapidly. The level of infection in your herd is up to you. Your herd veterinarian should be a valuable resource for assisting you in the elimination of Mycoplasma from your dairy. Be sure to use them.

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