Volume 61 | Issue 2 Article 4

1999 Mycoplasma in Cattle Tim Brandes Iowa State University

K. W. Kersting Iowa State University

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Recommended Citation Brandes, Tim and Kersting, K. W. (1999) "Mycoplasma Mastitis in ," 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 are considered Gram nega­ Mastitis is defined as of tive but stain better with Giemsa rather the mammary gland, usually due to mi­ than Gram stain.3 crobial . 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 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 , 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 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 . 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 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 '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. 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. 2 mastitis can be linked to the arrival of new animals, putting expansion herds at a Control greater risk. Culturing milk from newly arrived animals will help to identify car­ Because no effective treatment exists, the riers and assist farmers in making deci­ most important aspects of a mycoplasma sions before the infection is widespread. mastitis outbreak have to do with control­ Because one animal can shed large ling its spread. Fomites such as the milk­ amounts of the microorganism, screening ing unit, milkers' hands, and wash clothes of all new animals is important. Once an are capable of transmitting the organism animal has cultured positive, she should from cow to cow, so milking hygiene is an be segregated and milked last or culled important factor in reducing its spread. immediately. In addition, some research­ Cleanliness techniques such as single use ers believe respiratory shedding of towels, pre- and post-milk teat dipping, Mycoplsma bovis may infect the mammary wearing of rubber gloves, and disinfection gland of naIve animals, so some experts of the unit between cows have reduced the recommend culturing nasal secretions spread within a herd.5 from any new animals.2 In addition to the sanitary practices Because mycoplasma organisms are during milking, other steps may be neces­ shed in very high numbers from infected sary to reduce transmission between in­ animals, bulk tank cultures can be a very fected cows and clean cows. Culturing milk sensitive test of farm infection. A single from all mastitis cases and any fresh cows cow shedding the pathogen can be detected for Mycoplasma sp. and then separating from the bulk tank culture on a farm of and milking the positive cows last will help 400 head.14 This sensitivity gives veteri­ control spread. Also, using single use mas­ narians and farmers an early warning of titis treatment tubes for clinical cases of a possible outbreak. If the bulk tank is mastitis is beneficia1.5 positive, further culturing of individual treatment at dry-offfor the cows is necessary and the control mea­ other common mastitis pathogens is a re­ sures discussed earlier need to be imple­ warding and encouraged practice. How­ mented to prevent widespread infection on ever, this same procedure can be a source that farm. Also, it should be noted that a of spread of Mycoplasma bovis and care­ cow that cultures positive is considered ful measures should be followed not to use positive for life.s contaminated intramammary mastitis Milk from cows infected with Myco­ tubes. Because mycoplasma are resistant plasma bovis should be considered a pos­ in vivo to most commonly used drugs, an­ sible source of infection to calves consum­ tibiotic treatment on clinical cases is of- ing the milk. Mycoplasma bovis was

80 IOWA STATE UNIVERSITY VETERINARIAN recently isolated from a group of Holstein nal animals will be of great benefit in pre­ calves in Michigan diagnosed with otitis venting introduction to a naIve herd. Fi­ media. Investigators believe the calves nally, due to its ability to resist antibiot­ consumed milk from infected cows on this ics in vivo and its high degree of infectivity, known positive herd and this led to colo­ culling of any cows testing positive for my­ nization of the nasopharynx with exten­ coplasma should be considered.• sion into the auditory tubes and tympanic bullae. The same group of calves also had an increased incidence of respiratory in­ References fections due to Mycoplasma bovis. 15 The common practice of feeding calves dis­ 1. Owen WE, Watts JL. Laboratory procedures on bo­ carded milk from cows that have been vine mastitis. American Society for Microbiology Work­ shop 1993. treated for mastitis should be discouraged 2. Thomas CB. Mycoplasma mastitis:An emerging dis­ on farms known to be infected with this ease of midwest dairies? Solving Quality Milk Produc­ pathogen. tion Problems 1997; 39-48. 3. Quinn PJ, Carter ME, Markey B, et a1. Clinical Vet­ erinary Microbiology 1994; 320-321. Conclusion 4. Watts JL. Etiological agents of bovine mastitis. Vet­ erinary Microbiology 1988; 16:41-66. Mycoplasma mastitis is an emerging dis­ 5. Fox KL, Gay JM. Contagious mastitis. Vet Clin North ease in the dairy industry. Once thought Am 1993; 9:475-486. 6. Jasper DE. Bovine mycoplasma mastitis. Adv Vet to be primarily confined to California's Sci Comp Med 1984; 25:121-159. dairies, it is being diagnosed with increas­ 7. Gourlay RN, Howard CJ. Bovine mycoplasmas. The ing frequency across the country. Existing Mycoplasmas 1979; 2:49-102. herds buying outside replacements and ex­ 8. Boughton E. Mycoplasma bovis mastitis. Vet Bull 1979; 49:377-387. panding herds are at increased risk of in­ 9. Jasper DE. Mycoplasmas and bovine mastitis. troducing the problem. Although the tra­ Mycoplasmosis in Animals: Laboratory Diagnosis 1994; ditional mastitis bacteria are still the most 62-67. economically important problems to the 10. Bennett RH, Jasper DE. Bovine mycoplasma mas­ titis from intramammory inoculation of small num­ dairy industry, mycoplasma mastitis has bers of Mycoplasma bovis. Vet Microbiology 1978; devastated some farms undergoing expan­ 2:341-355. sion. Cows with multiple quarter mastitis 11. Fernald GW. Immunologic interactions between and no systemic signs of illness should be host cells and mycoplasmas. Rev Infect Dis 1982; 4:201- 204. considered possible cases and milk culture 12. Ball HJ, Campbell IN. Antibiotic treatment of ex­ should be used to confirm the diagnosis. perimental Mycoplasma californicum mastitis. Vet Rec Once a herd is diagnosed as Mycoplasma 1989; 125:377-378. bovis positive, steps should be taken to 13. Tyler JW, Culler JS, Ruffin DC. Immunization and immunotherapy for mastitis. Vet Clin North Am 1993; control its spread. Because the organism 9:537-549. is shed in such high numbers in the milk, 14. Gonzalez RN, Jasper DE, Bushnell RB, et a1. Re­ separating and milking the positives last lationship between mastitis pathogen numbers in bulk along with strict milking time hygiene are tank milk and bovine udder infections in California dairy herds. JAm Vet MedAssoc 1986; 189:442-445. beneficial in controlling spread within a 15. Walz PH, Mullaney TP, Render JA, et a!. Otitis herd. Culturing any new additions to a media in preweaned Holstein calves due to Myco­ herd before they are mixed with the origi- plasma bovis. J Vet Diagn Invest 1997; 9:250-254.

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