Many different factors offer partial explanations and all have to be considered in the management and control of mastitis. Unfortunately, only doing some of the essentials correctly is not good enough because a single failure in the control program may result in problems.

The traditional view of mastitis suggests that the cow, bacteria and the environment all play a role in determining whether or not mastitis occurs. Occasionally, when these factors all come into play at the same time, the risk of new infection is greater than when only one or two factors is involved. For example; a stressed, newly fresh cow, placed in a warm, wet and dirty environment is more vulnerable to new infections due to the interaction of all the factors.

Issues and Practical Considerations
Mastitis is caused almost exclusively by various bacterial species. Occasionally a case may be due to yeast or some other unusual organism but these are not the major concern. Many different bacteria species may cause mastitis but only a few species cause most of the mastitis problems.

The introduction of antibiotics to mastitis control, years ago, was initially considered a way to eliminate mastitis but it didn't take long for the appearance of bacteria strains that were resistant to the most common antibiotic, penicillin. This is not the case with all bacteria but certain species have this ability. As a consequence, newer penicillin derivatives as well as non-penicillin antibiotics have been developed in an attempt to maintain efficacy.

Some bacteria can resist or survive in the presence of certain antibiotics while others simply may not be susceptible to certain antibiotics.

Strep ag for example still responds well to penicillin treatments but in many instances Staph aureus will not. There may be several reasons for this. Certain Staph aureus strains may develop mechanisms that allow them to inactivate penicillin products, making them worthless. On other occasions Staph aureus may wall themselves inside of scar tissue infection pockets and the antibiotics cannot reach them. This is common in older Staph infected cows.

Antibiotic resistant strains of bacteria are also a significant human health issue. There is a growing public concern that bacteria are gaining increased resistance to commonly used antibiotics and on occasion no effective product is available to treat certain types of bacterial infection.

A viewpoint has developed that excessive antibiotic usage in animal agriculture is contributing somehow to increased bacterial resistance in humans. There are strong opinions on both sides but no absolute answer has emerged to date. It is prudent however for dairymen to use antibiotics as judiciously as possible and reduce the concern that we are contributing to the possible contamination of foodstuffs and creating bacteria that are antibiotic resistant.

The final piece of this puzzle is variation associated with different bacterial species. Mastitis caused by coliform type bacteria generally respond poorly to traditional antibiotics. They have an ability to resist many antibiotics so infusing or injecting animals, suffering coliform infections, with such materials is ineffective. This is why a case of coliform mastitis often does not respond to antibiotic treatment.

The point here is that management of a dairy should not rely too heavily on antibiotics to resolve mastitis problems They are helpful tools against a limited number of bacterial species and should only be used when necessary. Excessive use, use of the wrong antibiotic, or failure to follow label directions may result in treatment failure and increased risk of antibiotic contaminated milk which can be a very costly mistake. Be careful! 

Researchers have instead approached categories of bacteria, one at a time, in an attempt to develop a vaccine against select bacteria families. Vaccines equip the body with an improved defense mechanism against invading bacteria based on certain unique properties of the bacteria. It may be some component of the cell wall that triggers the response or an attachment mechanism that is the basis of the vaccine.

The problem is that within a species of bacteria there may be many variations and so it may require a separate vaccine against each variant. Ideally, if each variant contained some common feature, that feature may form the basis of a vaccine. That is what has been done in the case of the coliform mastitis vaccines available today. These vaccines cause the body to identify a common component of the many coliform strains and they react accordingly to develop resistance and offer protection.

What works against coliforms does not work against Staph aureus or Strep ag because these organisms have a completely different set of characteristics. Staph aureus have well developed tissue attachment mechanisms and that may be the basis of a vaccine whereas Strep ag have different features yet. It is likely each of these different species will require a different vaccine aimed at some unique characteristic that makes it vulnerable. It will take time to develop such products and when available they may have a limited spectrum. Users will have to assess the economics of using such products.

Prevention Techniques
The remainder of the mastitis control program is similar to controlling bacteria counts in raw milk. Objective one is to keep bacteria out of the tank by keeping things clean. The same applies to mastitis. Keep cows as clean as possible and minimize their exposure to mastitis causing bacteria. Clean, dry conditions, proper milking procedures and teat dipping with effective products are key components of an effective mastitis control program. There are no shortcuts and those who opt to try some, typically end up with a bigger problem at some later point.

Teat Dip Function
How do teat dips work to limit mastitis problems? Teat dips are topical antiseptics that are capable of killing bacteria on contact. They do not slow down bacteria growth or help the body mount a defense against bacteria. They kill bacteria on contact by one means or another depending on the active ingredient. Since they are used strictly externally they cannot eliminate existing infections. If they can contact bacteria for a brief period, they will kill them. This is the basis for their use in teat dips. The objective is to kill all the bacteria on the teat and teat end immediately after milking so that there are no bacteria to enter the gland.

This is why advisors focus so heavily on being certain teat dip is applied at every milking and that the method of application allows complete and total coverage of each teat. If the teat is not well coated with germicide there will be bacteria that go untouched and they will potentially cause mastitis.

In the overall effort to manage mastitis, antibiotics have a place, especially in dry cow programs. Their use in treating infections during lactation is considered to be somewhat limited, with the exception of treatment of Strep ag infections. Antibiotics are not the answer to many mastitis problems but on a select basis, with professional advice from a veterinarian, trained in mastitis work, they are valuable tools.

Vaccines are now appearing that have demonstrated effectiveness but they are narrowly focused at certain bacterial species. Vaccines that have demonstrated effectiveness against the coliform type bacteria are presently available and should be considered in a mastitis control program.

To date there are no effective, commercially available vaccines against environmental Streptococci such as Strep uberis and Strep dysgalactia. No effective vaccines or antibiotics are available to prevent or even effectively treat new infections caused by Pseudomonas, Serratia, Prototheca and the many other bacteria that occasionally cause mastitis. Immunizing dairy cows to prevent mastitis still has a ways to go.

1. Housing cattle so that they are clean, dry and comfortable.
2. Preparing the teats so that at the time of unit attachment each teat has been forestripped, sanitized and wiped dry.
3. Attaching teat cups with a minimum of air being admitted and adjusting units to properly hang on the teats.
4. Cluster removal at the end of milking after vacuum in the claw has been released. Minimize overmilking to eliminate teat end problems
5. Immediately after unit removal thoroughly coat each teat with a proven effective teat dip.
6. Infusing at dry off each teat with a dry cow antibiotic and sealing the teat by dipping it in a teat sealant.

Investment in preventing mastitis is always going to be more cost effective than post infection treatments and the associated losses in production etc. In this way mastitis is no different than most other industrial processes. The further the problem invades the process the more costly the eventual fix.