Mycoplasma Species and Mastitis

A group of organisms, Mycoplasma, are capable of causing a serious mastitis condition. Mycoplasma organisms are not true bacteria. They are much smaller in size compared to most bacteria but are larger than viruses.

Mastitis is caused by many different species of bacteria including Staph aureus, Streptococcus agalactiae and E. coli. In addition, other non-bacterial microscopic organisms occasionally cause similar problems. Species of yeast, Prototheca algae and Nocardia, a species of mold common in soil, occasionally cause serious mastitis problems, usually on an isolated basis. Often such forms of mastitis are difficult or impossible to treat because they do not respond to available antibiotic therapies.

Another group of organisms, Mycoplasma, are also capable of causing a serious mastitis condition. Mycoplasma organisms are not true bacteria. They are much smaller in size compared to most bacteria but are larger than viruses.

Mycoplasma lack true cell walls and many of the internal systems common to bacteria. They act as cellular parasites, gleaning basic molecular compounds from the host cells. They cannot make many of these compounds themselves, since they lack the chemical machinery. Despite these characteristics, Mycoplasma are capable of causing serious infection and a variety of illnesses in animals and humans.

Species of Mycoplasma

There are several species of Mycoplasma capable of causing cattle infections. They may cause pulmonary infections, middle ear infections, joint infections etc. Some, but not all species are also capable of causing mastitis. It is quite common for these other symptoms of Mycoplasma infectionj to be noted at the same time as mastitis problems are occurring.

When attempting to identify and resolve Mycoplasma problems, it is always beneficial to understand the organism involved. Other considerations include; how to spot problems, how to treat infections, risks to the overall herd, and how to minimize these risks.

Since Mycoplasma are unique organisms, it is especially important to determine if they are the cause of a mastitis problem. To date there is no effective tool for treating a Mycoplasma mastitis problem, so other control techniques have to be implemented.

Species of Mycoplasma-causing mastitis

There are several Mycoplasma species that may be involved with mastitis, but certain ones are more of an issue than others. The following list identifies potentially infectious species and their basic characteristics.

  1. Mycoplasma bovis - the most common cause of Mycoplasma mastitis. Estimated it is responsible for about 50% or more of the cases of mastitis caused by Mycoplasma.
  2. Mycoplasma bovigenitalium - found in reproductive tract of animals, may contaminate the teats when uterine discharges occur.
  3. Mycoplasma canadense - occasional cause of mastitis and quite resistant to heat treatment.
  4. Mycoplasma californicum - may cause mastitis
  5. Mycoplasma alkalescens - may cause mastitis
  6. There are several other species of Mycoplasma that may cause disease but they are not considered to be a significant cause of mastitis.

Other Diseases Associated with Mycoplasma Infection.

Calf middle ear infections

This condition may be caused by Mycoplasma infections. Affected calves tend to have characteristic droopy ears and/or head tilt. It can be fatal and treatment is not always successful. One way calves may contract this problem is through consumption of Mycoplasma contaminated waste milk. Calves, especially in group housing, may suck or chew each other and this may allow organisms on the mouth region to get to the ear and eventually cause new infections. There may also be other means of spreading and contracting the disease.

Joint swelling and lameness

Mycoplasma species can enter leg joints and infect the fluids therein causing swelling and lameness.

Respiratory infections (pneumonia)

Mycoplasma is known to be a common cause of respiratory tract infections. Infected animals that cough may actually expel the organisms into the air in tiny water droplets. These may float on air currents and possibly contaminate other animals. This may be more commonplace with confinement housing, especially if ventilation is inadequate.


Mycoplasma is unique in that it may be possible for organisms to move from an infection site in one part of the body (i.e. respiratory tract) to the mammary gland by internal relocation. This however is not the primary cause of herd outbreaks of Mycoplasma mastitis.

Quick Fact:

Mycoplasma is spread from udders of infected cows to non-infected cows primarily by contaminated milking clusters and hands during milking.

Minimizing these issues is critical in controlling Mycoplasma spread just as it is with other forms of contagious mastitis including Staph aureus and Strep ag.

Clean hands, clean clusters and post-milking teat dipping are critical control measures.

Mycoplasma mastitis has come to be a concern on many dairies. It has been recognized as a problem for many years in the larger dairies of California and Florida. In the 1970’s-80’s it produced serious difficulties for many large west-coast dairies and for a time was thought to be a large herd mastitis problem.

No longer. Most states have detected its presence and prevalence appears to be increasing in many areas. Herds buying cattle of unknown Mycoplasma status are vulnerable to the disease, especially if management is unfamiliar with the nature of this problem.

Herds that are built or expanded rapidly by purchasing and assembling cattle from various locations are the most vulnerable. Generally, there is no previous history on many of these animals. As a result, a significant amount of pre-purchase testing is required to screen out infected animals.

Relocation of large numbers of animals to new facilities results in stress which reduces disease resistance and increases susceptibility to disease producing agents, including Mycoplasma.

Once a cow develops a Mycoplasma clinical mastitis infection, most outcomes thereafter are negative. Cows often develop significant udder swelling as well as off-color and occasionally markedly different looking milk. They may actually develop infections in all quarters simultaneously, which is an unusual observation for mastitis. They may appear to recover spontaneously but generally remain carriers and will have occasional flare-ups and releases of large numbers of organisms.

Treatment with infusion tubes and/or systemic treatment produces no improvement for a simple reason. The antibiotics available, predominantly penicillin based products, tend to interfere with cell wall development. Since Mycoplasma have no cell wall,such antibiotics are ineffective.

Bacteriology of milk from infected cows

During clinical episodes, Mycoplasma infected quarters will shed huge quantities of organisms. Dr. Allen Britten, Udder Health Services, Inc., Bellngham, Washington has indicated that infected cows may shed billions of organisms into raw milk during clinical outbreaks. At other times they may shed very few. This pattern of shedding makes it difficult to always rely on bulk tank cultures as a way of determining if Mycoplasma is present. Nevertheless, routine bulk tank screening should be used as a monitoring tool to help determine if milk from Mycoplasma infected cows is entering the tank.

Mycoplasma impact on standard raw milk bacteria counts

Mycoplasma shedding will not impact the standard plate count (SPC), PI counts or the LPC, even if a lot of cows are shedding. These organisms require such unique conditions for growth that standard milk bacteria tests will not reveal them. Infected cows may have a significant somatic cell response, so the SCC will rise as a result of infections.


Minimize animal purchases. Untested new animals entering a herd may be the source of Mycoplasma infection.

Look at records from a herd being considered for purchase to determine if there has been a problem. If no such information exists, have a bulk tank milk sample taken and sent to a lab that has procedures in place to properly test for Mycoplasma. University veterinary diagnostic labs and certain private veterinary diagnostic labs are capable of doing this properly. The key is to work with a group familiar with testing and identifying Mycoplasma. Also, if Mycoplasma growth is found, ask for them to have it speciated to determine if the species is a likely cause of mastitis. Speciation requires specialized procedures that take additional time. Often the sample has to be sent to another facility equipped to do such [J3] work. Sequential bulk tank samples spanning several days would help increase the chances of detecting cows that may be shedding Mycoplasma organisms sporadically and at different concentrations.

Sick Pen Cows

There is always a concern about cattle in hospital facilities. It is a collecting point for all cows suffering a variety of ailments. Cows may go in with a sore foot, be exposed to mastitis while there, and emerge with a mastitis problem. When facilities allow, waste milk from the hospital string should be routinely sampled and evaluated for Mycoplasma and other, more standard, mastitis pathogens.

Any clinical mastitis case should be sampled prior to treatment and the sample frozen. If there is no response to treatment then the sample(s) should be tested to determine which organisms are present. Keep in mind that Mycoplasma is a very contagious organism, so if there is a Mycoplasma concern, get the sample tested promptly rather than accumulate several before testing.

Milking procedures and facilities are concerns in hospital facilities. If a separate milking facility exists, make certain that cows are milked in a manner that minimizes cow to cow transfer of potential pathogens. Milkers must wear surgical gloves and they need to sanitize hands and milking clusters between cows.

Quick Fact:

Cows infected with Mycoplasma mastitis should be identified, totally segregated from the main herd and culled immediately if they show clinical problems.

If they appear normal, they need to remain segregated until they are no longer productive or experience a clinical flare-up. Then they should be culled.

Cows can never be returned to the main herd even if they appear to have recovered because they may become chronic, occasional shedders.

Mastitis Treatment Products

Treatment of mastitis cases should only involve products labeled for intramammary infusion. They should be factory produced, unopened products.

Occasionally cows are treated with bottled medicines as additional supportive therapy. These materials often become contaminated, due to sloppy procedures, with Mycoplasma and become a source of new infections. This is also a problem with certain other organisms that can survive in medications including yeast, molds and Nocardia.

Infusion procedures

Proper infusion technique is critical when treating udder infections. Thoroughly clean the teat ends per the product label recommendations. Frequently a sterile gauze pad soaked with alcohol is used to effectively clean and sanitize the teat end. Infuse tube products using the partial cannula insertion method. Research has demonstrated that using a very short cannula to infuse product reduces steak canal keratin ream out and possible relocation of pathogens from the streak canal into the udder.

What sanitizers are effective?

Mycoplasma organisms contain no special characteristics that make them resistant to sanitizers. Iodine, especially with an acid base, is highly effective against Mycoplasma organisms when used as a hard surface sanitizer.

Automated backflush systems are available. When linked to an acid based iodine solution, clusters can be sanitized between cows to limit cow to cow transmission of Mycoplasma organisms by the milking cluster. It is advisable to put maximum effort into identifying infected cows and eliminating them, rather than relying exclusively on a backflush system as a means of limiting Mycoplasma transfer.

Iodine teat dips, especially products providing high levels of free iodine, will effectively kill Mycoplasma organisms on contact. They need to be used pre- and post-milking to sanitize teats. Teat dipping is a vital part of all mastitis control programs, including Mycoplasma mastitis.

Waste milk handling

Milk from cows being held out of the tank for various reasons is often used as calf feed. However, it frequently carries significant health risks due to pathogens. It may be contaminated with various mastitis pathogens including Staph aureus and Mycoplasma species. Heat treating waste milk to kill pathogens is advisable using pasteurization units available today.

Mycoplasma species are susceptible to heat treatment, but they differ in terms of time and temperature requirements for lethality. The following table provides the needed time and temperature exposure for killing three of the more common species.

Time needed to kill Mycoplasma pathogens (minutes)*

  140 F 149 F 153.5 F 158 F
M. bovis 5 2 1 1
M. californicum 10 2 2 2
M. canadense 30 10 5 3

*Butler et al. Journal of Dairy Science. October, 2000.

It is clear if M. canadense is involved, then more time will always be needed to kill it. At the highest temperature, 158 F, the time required is reduced to 3 minutes.


  1. Several species of Mycoplasma are capable of causing bovine mastitis. Mycoplasma bovis is the most commonly identified species.
  2. Purchased cows with unknown infection status are a common source of problems.
  3. Mycoplasma species may cause ear, respiratory tract and joint infections.
  4. Medications contaminated on-farm by improper handling procedures are a common source of problems.
  5. Mycoplasma udder infections are unresponsive to mastitis treatment products.
  6. Infected cows may shed huge numbers into raw milk during clinical periods.
  7. Mycoplasma organisms in raw milk will not be picked up by normal standard plate count (SPC) or preliminary incubation (PI) procedures, even when present in large numbers.
  8. Special growth procedures must be used to determine the presence of Mycoplasma in milk. Use labs familiar with these special requirements.
  9. Routine bulk tank screening is helpful to determine if infected cows are present and shedding.
  10. Infected cows must be identified and either segregated or culled to protect the rest of the herd. Segregated cows can never be allowed to re-enter the main herd.
  11. Primary means of Mycoplasma spread is cow to cow by contaminated milking clusters and hands. Milking time hygiene is critical in limiting spread of Mycoplasma.
  12. Iodine teat dips and sanitizers effectively kill Mycoplasma organisms.


Winston Ingalls

Winston Ingalls
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