Mycoplasma Mastitis in Dairy Cattle Tim Brandes Iowa State University

Volume 61 | Issue 2 Article 4 1999 Mycoplasma Mastitis in Dairy Cattle Tim Brandes Iowa State University K. W. Kersting Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/iowastate_veterinarian Part of the Bacterial Infections and Mycoses Commons, Large or Food Animal and Equine Medicine Commons, and the Veterinary Pathology and Pathobiology Commons Recommended Citation Brandes, Tim and Kersting, K. W. (1999) "Mycoplasma Mastitis in Dairy Cattle," Iowa State University Veterinarian: Vol. 61 : Iss. 2 , Article 4. Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol61/iss2/4 This Article is brought to you for free and open access by the Journals at Iowa State University Digital Repository. It has been accepted for inclusion in Iowa State University Veterinarian by an authorized editor of Iowa State University Digital Repository. For more information, please contact [email protected]. Mycoplasma Mastitis in Dairy Cattle TIM BRANDES, DVMt AND K.W. KERSTING, DVM, MStt Introduction a characteristic "fried egg" microcolony. These bacteria are considered Gram nega Mastitis is defined as inflammation of tive but stain better with Giemsa rather the mammary gland, usually due to mi than Gram stain.3 crobial infection. Many organisms have Over 100 Mycoplasma species have been known to cause mastitis including been identified to date, with more yet to bacteria, fungi, and yeast. Mastitis is the be named.2 Of the Mycoplasma species dis most economically important disease of covered, eight have been isolated from the the dairy industry, the condition has been bovine udder. By far the most frequent iso~ estimated to cause as much as two billion late recovered is M. bovis, but others such dollars in lost income for United States as M canadense, M. bovigentalium, and M. dairy producers at a cost of $181 per cow californicum have also been cultured. 4 per year. 1 The biggest losses are due to Mycoplasma require special medium lowered production, but discarded milk, on which to grow. Beef infusion is the ba drugs, veterinary costs, and premature sic medium with 20% serum, yeast extract, culling also contribute to the losses. DNA, and other growth factors added. More than 130 different microorgan Along with the special medium, penicillin isms have been isolated from the mam and other antibiotics are added to aid in mary gland of the bovine with the major selection of Mycoplasma versus other bac ity of infections due to staphylococci, teria.3 Because these organisms lack a cell streptococci, and coliforms. However, my wall, beta-lactam antibiotics can be added coplasmas have begun to cause significant to the culture media and the growth of problems in some dairies. The first re mycoplasma is not affected. ported cases of mycoplasma mastitis were In vitro, mycoplasma species are sus in Europe in 1960. Since that time it has ceptible to antibiotics which act in other been found all around the world, includ ways besides inhibiting cell wall synthe ing the United States. Traditionally, Cali sis. However, the organism in vivo must fornia was most affected, but the disease function as a parasite in close contact with has now become a problem across the en host cells. Because of this close contact, tire country. 2 these microorganisms can obtain precur sor molecules from the host and thus be The Organism fairly resistant to the antibiotics that act by inhibiting bacterial protein synthesis.5 Mycoplasma are the smallest prokaryotic cells that can self-replicate. Their genomes Clinical Signs are simple and one-fifth the size of the av erage bacteria. These organisms do not As stated, the species most often impli have the genetic capability to produce a cated in mastitis is Mycoplasma bovis. cell wall, and are enclosed in a plasma This microorganism is a common inhabit membrane. Mycoplasmas can take many ant of the bovine upper respiratory tract, individual forms, including cocci, spirals, and is often involved in Bovine Respira filaments, and rings, but they all grow in tory Disease Complex and Enzootic Pneu monia of calves.6 Some other less common diseases 'Dr. Tim Brandes is a 1998 graduate of the Iowa State which have been linked to Mycoplasma University College of Veterinary Medicine. bovis are arthritis/synovitis, genital tract ttDr. K. W. Kersting is Associate Professor in the Depart 7 ment of Veterinary Diagnostic and Production Animal infections, abortion, and otitis media. Medicine at the ISU College of Veterinary Medicine. However, this discussion will be limited to 76 IOWA STATE UNIVERSITY VETERINARIAN mastitis. duce direct damage. Metabolic end prod Cows should be suspected of having a ucts and toxins can damage host cell mem Mycoplasma species infection if they have branes, and cause tissue damage.5 The severe purulent mastitis and no other sys host's own immune response causes tissue temic signs. Cows typically have mastitis destruction by a large inflammatory reac in more than one quarter, with a sharp tion of neutrophils, macrophages, plasma drop in milk production, sometimes ap cells, eosinophils, and fibroblasts. Initially proaching agalactia. Milk appearance can the alveoli and milk ducts fill with neu be tannish to brown with flaky sediment.6 trophils and the epithelium of the ducts However, milk appearance is not a sensi begin to divide, eventually filling the duct. tive indicator for early infection and re Meanwhile, alveolar epithelium undergoes searchers have discovered that 106 to 108 the opposite reaction: cells involute, milk colony forming units of Mycoplasma bovis production drops, and the cistern fills with per milliliter of milk can be shed for two exudate. Where the reaction is severe, the to three days preceding any changes in alveoli and ducts are replaced by fibrous milk appearance. The California Mastitis scar tissue and are permanently lost; the Test will be negative the first two to three areas less severely affected may begin pro days of infection but from three to seven ducing milk again but at a lower level. days post infection both CMT and milk ap Cows typically have numerous abscess in pearance will indicate mastitis. At some their mammory glands, ranging in size point during the initial week of infection from microscopic to ten centimeters in di the cow's milk production will drop dra ameter.5 Generally, the host's immune re matically and not rebound for months.2 sponse to Mycoplasma bovis is considered Despite the involvement of more than one reactive versus protective. The reactive quarter and severe inflammation the in response leads to necrosis of mammary fected cows rarely go offfeed or elicit a fe tissue and established foci of infection, ver.8 causing reduced milk secretion. In addi Mycoplasma bovis can occasionly in tion, the abscesses are known to harbor fect quarters where other pathogens al viable Mycoplasma bovis, which may be ready occur, allowing for variation in clini responsible for long-term intermittent cal signs depending on the other bacteria shedding by infected cOWS. 5,11 involved. Also on occasion cows can shed this organism and never show clinical Diagnosis signs, complicating control and outcome of an outbreak. It should be noted that be If cows are showing the clinical signs dis cause of a cow's ability to shed Myco cussed earlier, quarter and composite milk plasma bovis for variable amounts of time, samples from cows suspected of infection she should be considered positive for life.9 should be submitted for culture. Enriched media is used to isolate this organism, and Pathogenesis a special request is often required by the veterinarian in order for the laboratory to Along with the common mastitis bacteria conduct the culture for Mycoplasma sp. Staphylococcus aureus and Streptococcus Samples should be kept cold or may be fro agalactiae, Mycoplasma bovis is consid zen for up to two weeks before arrival at ered a contagious pathogen, thus infection the laboratory. The milk is then plated is spread during the milking procedure. directly on to the mycoplasma media and Because as few as 70 colony forming units incubated at 37°C in a five to ten percent per milliliter can cause infection, M. bovis C02 atmosphere. Usually growth can be can be spread easily from cow to cow with seen in two to three days, but some myco poor milking hygiene, contaminated equip plasma require up to six or seven days of ment, and via milkers' hands.10 incubation before growth is seen. Another Although the majority of tissue dam helpful diagnostic step is routine cultur age is due to the cow's own immune re ing of the bulk tank; this can help moni- sponse, mycoplasma themselves can pro- continued on page 80 VOL 61, No 2; FALL 1999 77 tor a herd for early infection. If culture is ten futile and not recommended.12 positive, individual cows can be cultured Experimental vaccines for prevention in order to identify individuals with mas of m:ycoplasma arthritis have given re titis. searchers hope in prevention of mastitis Culturing is the test of choice for con through vaccination. The few cows that are firming a suspected case. However, in or able to clear the infection on their own are der to identify the species of mycoplasma, less inclined to become reinfected. How different tests are required. ever, attempts at protection through Imunofluorescence and immunoblotting parenteral and intramammary immuniza on colonies transferred to a nitrocellulose tion have been disappointing. Both modi membrane are the common methods used fied live and killed Mycoplasma bovis vac to differentiate species. Because Myco cines have been used and neither was plasma bovis is considered the most patho proven to be effective. These experimen genic mycoplasma that causes mastitis, it tal trials have elicited a humoral response, is important to identify isolates down to but this has not been proven to be protec- the species in order to take the appropri tive against mastitis.13 ate control measures and reduce spread Many herd outbreaks of mycoplasma to naIve cows.

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