Article after article appears in scientific journals and dairy magazines regarding the subject of mastitis and the many causes. Readers likely become somewhat immune to the standard advice which typically boils down to: milk clean, dry cows using proper milking procedures and functionally adequate milking systems, teat dip each teat after unit removal, dry treat each quarter at dry off and treat infected cows and cull chronically infected cows. The message makes it appear so simple that it may be difficult to believe that anyone would have a mastitis problem. There must be something more complicated or different that is involved and occasionally there may be.

Mastitis has been defined as an infection of the mammary gland and the cause is invariably bacteria of one type or another. Contagious bacteria such as Staph aureus and Strep ag are well known but still persist on many dairies. Other mastitis causing bacteria include the coliforms, which are commonly found in the environment of the cow, especially in the bedding. In addition to the coliforms there are several species of environmental Streptococci which may cause problems. These include Streptococci uberis and Streptococci dysgalactiae. While coliforms and the environmental Streptococci are common causes of mastitis, dairymen and veterinarians are familiar enough with these bacteria that they can implement control strategies.

Occasionally there appears in a herd a mastitis problem that is unusual and may result in a lot of problems and it may prove very costly. When this occurs it requires that everyone involved be aware that certain unusual mastitis causing organisms exist and if suspected, quick action must be taken to identify the problem and implement effective control procedures. Don't be surprised if these control procedures are rather drastic and in some cases quite costly. Following are some examples.

Mycoplasma Mastitis
Mycoplasma is a term for a group of organisms that are classified as neither bacteria nor viruses. Several species that have been reported as associated with mastitis, but two or three have been the predominant problem. At one time it was thought to be limited to only a few locations with California being the primary region. Based on better mastitis screening and reporting procedures it is likely that these organisms are present and associated with mastitis in most states. If you milk cows this organism can be an issue regardless of location. Documented cases of Mycoplasma mastitis often describe several typical observations that may be symptomatic of the problem.

Individual cows may have persistent, ongoing mastitis problems and various treatment products prove ineffective. This may suggest Mycoplasma. More than one quarter of a cow may be affected at the same time and occasionally, all four quarters may be impacted simultaneously. This again suggests Mycoplasma. Milk from affected quarters may take on characteristics that are not typical of mastitis caused by Staph or Strep organisms. It may have an orange or brown appearance and occasionally there appears sandy or flaky appearing material that settles to the bottom of milk samples. On occasion milk from infected cows may appear quite normal. Mycoplasma infections can lead to significant elevations of the somatic cell count and infected cows may shed large numbers of the organisms into the milk.

Culture work on milk samples, from individual cows or bulk tank samples, using standard growth media and procedures, normally fails to reveal the presence of these organisms. Many cows in a herd may show symptoms of infection before the diagnosis is finally made that this is the problem. The reason is that detection and identification of this organism requires a special growth media and the time frame for culture work is much longer than for standard bacteria determination. Unless the microbiology laboratory is specifically set up to do this work, and is asked to do so, it will not be detected. This can lead to an extended period of herd problems because the organism can rapidly spread from cow to cow by the milking clusters and the hands of people doing the milking.

There are no approved treatment products capable of eliminating this organism from infected glands. Approved antibiotics for treating lactating or dry cows are usually ineffective against this organism because it is not a true bacterium. Many of the available antibiotics tend to kill bacteria by disrupting certain vital functions of the cell wall. Mycoplasma does not have a true cell wall therefore traditional antibiotics are ineffective.

Control must aim at several areas. The organism is considered highly contagious and may be associated with other herd health problems including respiratory infections, swollen joints and middle ear infections that result in animals displaying a droopy ear and tilted head. Being aware that these symptoms and a difficult to control mastitis problem may be associated could allow earlier detection of a problem. Preventing the problem involves several common sense actions.

First, protect against introducing the problem into a clean herd by unknowingly purchasing infected cattle. This is a common way of contracting the problem. When the people involved are unfamiliar with Mycoplasma, which is often the case, the problem may create major damage before it is identified and control programs implemented. In unsuspecting herds, large or small, it may wipe out a large portion of the cows before it is identified and contained.

Bulk tank screening, when done properly, will reveal the presence of Mycoplasma in the herd. When identified, it is important to act promptly to identify infected animals and either cull them, which may pose an economic hardship, or segregate and handle them as an isolated and separate group. The key is to keep infected cows away from uninfected cows. This means totally separate equipment and facilities. Cows in the infected groups may eventually be culled.

The need to prevent cow to cow transfer of Mycoplasma organisms is sometimes credited with being the reason automated backflush systems were developed and that likely is the case. Sanitizing milking clusters between cows minimizes spread of the organisms from cow to cow and tends to lessen this means of spread. Typically an acidified iodine solution is run through the unit and after 30 seconds it is then flushed out. This will reduce the possibility of organism transfer. The key to Mycoplasma control however, primarily involves identifying and segregating infected cows.

Prototheca
Another organism that occasionally surfaces in mastitis problems is termed Prototheca. It also is not a bacteria and as a result, medicinal remedies that help control bacterial forms of mastitis will not control this problem. This organism is classed as an algae and tends to live in wet locations, such as mud puddles and other standing water sources. It will clearly show up on standard bacteriology growth media but may be incorrectly identified if the evaluator is unfamiliar with characteristics of the organism.

Antibiotics are ineffective since it is much different organism than typical mastitis causing bacteria. A difficult decision confronts the manager where this is a problem. It appears that the organism will survive the dry period and it appears it may also be spread from cow to cow by milking units and the hands of the milkers.

Minimizing opportunities for cattle to be in wet areas is suggested but there are obviously times when this is not easily accomplished. Culling infected cows is typically recommended in order to reduce the likelihood of infected cows infecting non-infected cows but this is an expensive proposition. Why it becomes a problem on one dairy and not on others is unknown, but that appears to be the case. Once a dairy develops a problem, it may be a persistent issue for an extended period. Infected cows are reported as going dry and then developing the problem after calving. Likely the organism survives in the dry udder because dry cow treatment antibiotics do not kill it.

Water Associated Bacteria
Water is one of the necessities for bacterial survival. Bacteria need the same things humans to survive; food, water and warmth. These basics are readily available on dairies and occasionally they lead to problems. Serratia is a bacteria strain that has been found in association with contaminated water supplies, bedding, and on occasion it has been reported to survive in quaternary ammonia and chlorhexidine digluconate teat dips. It is considered an environmental bacterium, meaning that environment to cow spread or transfer is the predominant cause of new infections rather than cow to cow transfer. Serratia marcescens is the most common species associated with mastitis but there are others species as well. This particular species has the ability to produce a pink colored pigment and, if present, may be a clue when evaluating a problem.

Serratia species are Gram negative bacteria indicating they have certain similarities to coliform bacteria, which are also Gram negative. They can produce new infections capable of causing elevated somatic cell counts and Serratia infections appear to cause longer term infections than is typical of other Gram negative, environmental bacteria such as E. coli or Klebsiella.

There is evidence to suggest that the dry period is a time of susceptibility to Serratia infections. Also, older, multiple lactation cows appear to have a tendency to be more susceptible to such infections.

Antibiotic therapy may be of limited value due to the Gram negative characteristics, much like a coliform problem. Available antibiotics are generally ineffective against these type bacteria so it is unlikely this approach will rid the herd of a problem. Managing the dry cow areas, free-stalls and milking clean dry cows are critical in controlling this problem and certain cows may have to be culled. Herds experiencing elevated somatic cell counts and no apparent problems with Staph auerus or Strep ag need to check for the presence of this organism.

Pseudomonas Bacteria
These bacteria are specifically associated with water and wet conditions. They are not typically a major cause of mastitis but in certain herds under certain conditions they may create a troubling mastitis problem. They can also be involved with milk quality concerns. Pseudomonas bacteria have some unique characteristics. They are Gram negative bacteria and typically are found in the environment. As Gram negatives they share certain characteristics with coliforms and other Gram negatives, one of which is resistance to many of the commonly used antibiotics. This means treatment with antibiotics is not likely to be a viable solution in helping eliminate the problem.

Pseudomonas bacteria have a somewhat unique ability to adhere strongly to surfaces such as plastic tubing, rubber hoses and even stainless steel. They may then coat themselves with a protective coating of material that is very resistant to all commonly used sanitizers including chlorine, iodine, quats etc. Once deposits of this material develop it is virtually impossible to kill them by routine short-term exposure to sanitizers. If some of the material is loosened from the surfaces and moved elsewhere, it may colonize the new area. When that location is the mammary gland it produces mastitis.

The actively growing and reproducing bacteria, not encased in the tough protective coating, are not resistant to exposure to quality germicides. It is the protected bacteria that develop the resistance and they are the source of the problems. Pseudomonas aeruginosa is one of the species that has been associated with significant mastitis problems in certain herds. Stagnant water, especially at a warm temperature, can be a major contributor. The bacteria are considered to transfer from the environment to the cow rather than cow to cow. Milking a clean, dry udder is critical in terms of reducing the possibility of this water borne bacteria gaining entry to the udder.

Antibiotic treatment with standard remedies is not likely to produce cures. Pseudomonas mastitis may reveal itself as cows with mastitis that is non-responsive to treatments and have prolonged clinical symptoms. If culture work positively identifies the organism as Pseudomonas the attending veterinarian may be able to offer treatment assistance but the key at that point is to identify the source and typically it will be water related. Wet lots and muddy conditions, milking wet teats, udders with long hair that harbor dirt and bacteria, old hoses that are used to apply water or udder washes to the teats and udder. Eliminating these issues will improve the situation and lessen this type of mastitis.

Other Pseudomonas species may be found in water. When such water is used in rinsing milk contact surfaces or somehow enters the system they may enter the milk that is added to the tank. They proceed to grow quite well under refrigerated conditions and can lead to elevated preliminary incubation (PI) counts since they tend to be cold tolerant.

Mastitis control should always focus on the common contagious and environmental mastitis causing bacteria. If an occasion arises however, when all these issues appear under control and yet a significant problem exists, consider these organisms as possible culprits in the endless battle to control mastitis.

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