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Mycoplasma bovis

obovis
Contributor(s):

Veronica Fowler

Al Manning

Synonym(s): M. bovis


Introduction

Classification

Taxonomy

  • Phylum: Tenericutes.
  • Class: Mollicutes.
  • Order: Mycoplasmatales.
  • Family: Mycoplasmataceae.
  • Genus: Mycoplasma.

Etymology

  • From the Greek 'Myco', meaning 'fungus' and 'Plasma' meaning 'formed'.
  • 'bovis' - of the ox.

Morphology

  • Atypical bacteria: mollicutes do not have a rigid cell wall but a three-layered flexible cell membrane.
  • Mycoplasma are characterized by their small cell size (typically 0.3-0.8 µm).
  • Under microscopy, Mycoplasma bovis forms fried-egg shaped colonies on mycoplasma culture agar.

Resting Forms

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Clinical Effects

Epidemiology

Lifecycle

  • Hematogenous spread within the animal. Intracellular pathogen.
  • Biofilm production contributes to bacterial survival in the environment and its persistence inside the host.
  • M. bovis is able to evade host defenses through variance in the cell surface proteins due to chromosomal recombination events during cell replication.
  • Animal immune response:
    • Initial clearance by macrophages.
    • Can invade erythrocytes and other blood cells and this is a useful mechanism for evading the host immune response.

Transmission

  • M. bovis is typically associated with contagious mastitis Mastitis: approach to the herd mastitis problem, ie spread during the milking process.
  • It is shed in respiratory surface secretions and can be transmitted by aerosols through coughing; there is initial colonization of the tonsils.
  • Infected cows shed M. bovis in their milk and can pass the bacteria onto their calves.
  • Bacteremia and hematogenous spread leads to the variety of clinical presentations.
  • There is a large variation in shedding between infected animals. Intermittent shedding has been reported in cows with mastitis. Shedding can occur for months/years.
  • Asymptomatic carrier animals and/or those with only mild clinical symptoms, which have not been detected by stock keepers, are hypothesized to be an important source of infection, but the evidence base to support this theory is currently lacking.

Pathological effects

  • M. bovis is typically associated with respiratory disease Adult respiratory disease, otitis media, mastitis Mastitis: unusual forms overview, and arthritis:
    • Respiratory disease: M. bovis can cause both acute and chronic respiratory disease, both as a sole pathogen, and also in association with other respiratory pathogens as part of the pneumonia complex Pneumonia. M. bovis pneumonia can affect calves and adult cattle. Histologically the pneumonia is seen as a peribronchiolar lymphoid hyperplasia (cuffing) or as a chronic caseonecrotic pneumonia (often in association with another organism), with multiple foci of dry caseous necrosis. Symptoms include:
      • Coughing.
      • Not typically associated with pyrexia, but a mild fever may be present.
      • Depression.
      • Poor growth rates.
      • Pneumonia that is unresponsive to treatment or relapses.
    • Otitis media:
      • Ear pain.
      • Head shaking.
      • Ear droop and ptosis, progressing to head tilt and circling.
      • Unilateral or bilateral.
      • Rare to see discharge from the ear.
    • Mastitis:
      • Clinical or subclinical in both lactating and dry cows.
      • Clinical cases tend to be sporadic in the UK, but more widespread outbreaks have been reported in the US.
      • Response to treatment is often poor.
      • Reduced yields.
      • Raised Somatic Cell Counts (SCC)
      • Purulent or serous udder exudate: a rice-like sediments has been reported, but this is not pathognomic.
    • Polyarthritis:
      • Multiple swollen joints, with heat and non-weight bearing lameness.
      • Typically affected joints are in the distal limb, eg the carpus and tarsus are the most affected joints.
    • Conjunctivitis and ocular disease have been reported as presenting signs. This may include exophthalmos.
  • M. bovis has also been identified in cattle with reproductive disease and anemia, although it may be incidental.
  • Other Mycoplasma spp have been identified in cattle and can be isolated from bulk milk, although the clinical significance of all species is not clear. Some strains have been reported to cause similar symptoms to M. bovis, eg M. alkalescens, M. boviculi, M. dispar, M. mycoides subsp mycoides (contagious bovine pleuropneumonia), M. wenyonii Mycoplasma wenyonii.

Control

Control via animal

  • Many farms do not need to employ any specific control measures beyond surveillance.
  • On farms with a diagnosed history of M. bovis or in a suspected outbreak the following control measures should be employed:
    • M. bovis mastitis is typically spread through milking equipment, so known affected cattle should be isolated in a different airspace and milked last. Ideally, they would be milked separately using a different cluster and milking line. Clusters should be disinfected after milking cows known to be infected. Where separate milking equipment cannot be used, then milking order should be: fresh cows, 1st lactation heifers, uninfected higher parity cows, high cell count cows, then confirmed cases.
    • M. bovis can also be spread through aerosols, so affected cows and calves should be isolated from healthy stock in a separate airspace CowSignals: air and group sizes should be minimized, ideally with fixed groups and “all in all out” policy. Affected animals should be segregated. Wear gloves when handling calves. Improve ventilation Ventilators. Control other causes of pneumonia.
    • Colostrum: avoid pooled colostrum or consider pasteurization Colostrum: overview or acidification Milk acidification. Ensure all feeding equipment is thoroughly disinfected between calves. Don’t feed affected cow’s milk to calves.
    • Milk feeding: pasteurized whole milk or consider powdered milk feeding. Avoid feeding waste milk. Acidified milk feeding may also reduce the spread of Mycoplasma bovis Feeding milk and milk replacers to calves Milk acidification.
    • Historically culling has been recommended as a control strategy, however this is not supported by recent published evidence.
    • Ideally avoid buying in any stock. Where replacements are needed, the next best option is to purchase non-lactating heifers from herds with no history of M. bovis. When buying older cattle, access to milk recording data is essential. Animals should not be brought in if they have any milk recordings >100,000 cells/ml. Bought in animals should be checked for signs of mastitis within 7 days, and be quarantined for 28 days before entering the milking herd.
    • Semen donor bulls should be antibody negative. Semen can be tested to ensure it is not contaminated, although few labs offer this service.

Control via chemotherapies

  • M. bovis has no cell wall and so is not susceptible to beta lactam antibiotics.
  • M. bovis does not synthesis folic acid and so sulphonamide antimicrobials are ineffective.
  • Based on in vitro susceptibility testing, M. bovis is sensitive to antimicrobials that interfere with protein or DNA synthesis, such as the tetracyclines Oxytetracyclines, macrolides Tulathromycin, lincosamides Lincomycin, florfenicol Florfenicol and fluoroquinolones Enrofloxacin.
  • At the time of publishing there is no standardized method for antimicrobial resistance testing for M. bovis. Ayling et al found increasing MIC values between 2004 and 2009 isolates for chloramphenicol, oxytetracycline and the fluroquinolones, which is suggestive that resistance may be developing.
  • Several antimicrobials are specifically licensed for treatment of Mycoplasma spp, including macrolides, tetracyclines and amphenicols:
    • Emphasis should be placed on diagnosing M. bovis and targeting treatment, rather than blanket treating, so as to promote responsible use of antimicrobials.
    • For treating M. bovis calf pneumonia, the treatment of choice is a long acting macrolide, eg tulathromycin Tulathromycin, gamithromycin. This class of antimicrobials are classified as ‘high priority critically important antimicrobials’ by the (World Health Organization and their use should therefore be avoided as a first line One health.
  • There are no evidence-based treatments licensed for mastitis caused by M. bovis. Veterinary advice should focus on diagnostics, controlling spread and preventing new cases.
  • There is limited research to demonstrate efficacy against M. bovis causing lameness. Oxytetracycline Oxytetracycline is often used empirically, however the prognosis is guarded. Joint flushing can be attempted in a hospital setting Joint lavage.
  • Non-steroidal anti-inflammatory drugs are recommended for all M. bovis infections on welfare grounds Anti-inflammatory drugs: overview.

Control via environment

  • M. bovis can enter the herd via cows milk/colostrum.
  • M. bovis can spread via direct contact, aerosols and fomites.
  • M. bovis has been reported to survive in the environment for many months.
  • When managing M. bovis respiratory disease on calf rearing units an ‘all-in-all-out’ system is recommended, with thorough disinfection between batches of calves.

Vaccination

  • Several companies produce autogenous vaccines based on farm specific strains of M. bovis, although there is limited evidence to support their use.
  • There is a bacterin vaccine licensed in the USA and available in Europe through an import license. It is licensed for protection against respiratory and joint disease, though published trial work is limited. 

Diagnosis

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Manning A (2020) Mycoplasma spp. mastitis - approach to diagnosis. Livestock 25 (4), 170-172 MAGOnline.
  • Haapala V, Pohjanvirta T, Vähänikkilä N et al (2018) Semen as a source of Mycoplasma bovis mastitis in dairy herds. Vet Microbiol 216, 60–66 PubMed.
  • Gille L, Boyen F, Van Driessche L, Valgaeren B et al (2018) Short communication: Effect of freezer storage time and thawing method on the recovery of Mycoplasma bovis from bovine colostrum. J Dairy Sci 101 (1), 609-613 JDairySci.
  • Parker A M, Sheehy P A, Hazelton M S, Bosward K L & House J K (2018) A review of mycoplasma diagnostics in cattle. J Vet Int Med 32 (3), 1241-1252 WileyOnline.
  • Timonen A A E, Katholm J, Petersen A, Orro T et al (2018) Elimination of selected mastitis pathogens during the dry period. J Dairy Sci 101 (10), 9332-9338 JDairySci.
  • Parker A M, House J K, Hazelton M S, Bosward K L et al (2017) Bulk tank milk antibody ELISA as a biosecurity tool for detecting dairy herds with past exposure to Mycoplasma bovis. J Dairy Sci 100 (10), 8296-8309 JDairySci.
  • Lysnyansky I & Ayling R D (2016) Mycoplasma bovis: mechanisms of resistance and trends in antimicrobial susceptibility. Front Microbiol 27 (7), 595 PubMed.
  • Barberio A, Flaminio B, De Vliegher S, Supré K et al (2016) Short communication: In vitro antimicrobial susceptibility of Mycoplasma bovis isolates identified in milk from dairy cattle in Belgium, Germany, and Italy. J Dairy Sci 99 (8), 6578-6584 JDairySci.
  • Nicholas R A J, Fox L K & Lysnyansky I (2016) Mycoplasma mastitis in cattle: To cull or not to cull. Vet J 216, 142-147 SciDirect.
  • Parker A M, House J K, Hazelton M S, Bosward K L et al (2016) Milk acidification to control the growth of Mycoplasma bovis and Salmonella dublin in contaminated milk. J Dairy Sci 99 (12), 9875-9884 JDairySci.
  • Nielsen P K, Petersen M B, Nielsen L R, Halasa T & Toft N (2015) Latent class analysis of bulk tank milk PCR and ELISA testing for herd level diagnosis of Mycoplasma bovis. Prevent Vet Med 121 (3-4), 338-342 SciDirect.
  • Piccinini R, Gosney F, Snel G G M, Luini M V & Nicholas R A J (2015) Environmental survival of Mycoplasma bovis on a white veal farm. Vet Rec Case Reports (1), e000207 BMJ.
  • Britten A M (2012) The role of diagnostic microbiology in mastitis control programs. Vet Clin North Am Food Anim Pract 28 (2), 187-202 SciDirect.
  • Justice-Allen A, Trujillo J, Corbett R, Harding R et al (2010) Survival and replication of Mycoplasma species in recycled bedding sand and association with mastitis on dairy farms in Utah. J Dairy Sci 93, 192-202 JDairySci.
  • Caswell J L & Archambault M (2007) Mycoplasma bovis pneumonia in cattle. Anim Health Res Rev (2), 161-186 PubMed.
  • Godden S, Mcmartin S, Feirtag J, Stabel J et al (2006) Heat-Treatment of bovine colostrum. II: Effects of heating duration on pathogen viability and Immunoglobulin G. J Dairy Sci 89, 3476-3483 JDairySci.
  • Biddle M K, Fox L K & Hancock D D (2003) Patterns of mycoplasma shedding in the milk of dairy cows with intramammary mycoplasma infection. JAVMA 223 (8), 1163-1166 JAVMA.
  • McAuliffe L, Ellis R J, Ayling R D & Nicholas R A J (2003) Differentiation of Mycoplasma species by 16S ribosomal DNA PCR and denaturing gradient gel electrophoresis fingerprinting. J Clin Microbiol 41 (10), 4844-4847 PMC.

Other sources of information

  • Animal & Plant Health Agency (2020) GB Cattle Disease Surveillance Dashboard. Website: https://public.tableau.com
  • UK-Vet Livestock Healthy Herd digital conference (2020) Mason C. The Clinical Syndromes Associated with Mycoplasma Bovis Infection in Cattle.
  • Animal & Plant Health Agency (2020) GB Cattle Disease Surveillance Dashboard. Website: www.public.tableau.com.
  • Animal & Plant Health Agency (2018) Mycoplasma Bovis: Current Knowledge, Industry Challenges and Knowledge Gaps for other UK Cattle Industry. UK Cattle Expert Group 2018. Website: apha.defra.gov.uk (pdf download).
  • Smith B P (2009) Large Animal Internal Medicine. 4th edn Mosby Elsevier, USA.
  • Guard C (2007) Musculoskeletal Disorders. In: Rebhun’s Diseases of Dairy Cattle. 2nd edn. Eds: Divers T J & Peek S F. Saunders Elsevier, USA. pp 467-503.
  • Hillman R & Gilbert R O (2007) Reproductive Diseases. In: Rebhun’s Diseases of Dairy Cattle. 2nd edn. Eds: Divers T J & Peek S F. Saunders Elsevier, USA. pp 395-446.

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