Additional Information on Mycoplasma Bovis

Posted by Dr. Brian Dorcey on July 13 2009 13:39

Mycoplasma bovis - 3 clinical syndromes:

• Feedlot pneumonia/arthritis
• Mastitis
• Calf pneumonia/arthritis/otitis media

An emerging cause of bacterial pneumonia in cattle

Mycoplasma bovis*

• M. bovirhinis
• M. arginini
• M. dispar
• M. californicum

*Most common/significant

Mycoplasma bovis -Feedlot pneumonia/arthritis

Clinical signs:

• Acute - chronic pneumonia
  
  • Nasal discharge
  • Depression
  • Rapid respiration
• Polyarthritis (may or may not be seen)
  
  • Affects lower joints: elbow, knee
  • Light and heavy cattle affected
  • Predominantly  fall/winter following cold exposure and stress
  • Morbidity < 80%, commonly 10-20%
  • Mortality 30-50% of affected cattle
• Post-mortem lesions
  
  • Bronchopneumonia with multiple small abscesses
  • Joint taps - clean serous fluid
  • Small abscess of joint capsules and tendon sheaths

Mycoplasma bovis - calf pneumonia/arthritis/otitis media

Clinical signs:

• Typical signs of pneumonia
• Head tilt
• Recumbency
• Post-mortem lesions:
  • Bronchopneumonia with abscessation
  • Middle ear
    • Partial - complete filling of tympanic bullae with caseous debris or serosanguinous fluid
    • Remodeling of the exterior surface of the tympanic bullae

Transmission

• Mycoplasma bovis is a natural inhabitant of the respiratory tract, vagina, and mucus membranes of healthy animals
• Most transfer of mycoplasma within herds occurs at milking time by milking machines, teat cups, and on the milker's hands
• It has been demonstrated that young calves fed M. bovis-infected milk have higher rates of respiratory infections and lateral transmission of respiratory infections may occur as long as 9 months after initial infection.
• Respiratory M. bovis infections on the farm have been linked to outbreaks of mastitis

Mycoplasma bovis - calf pneumonia/arthritis/otitis media

• Cause - feeding of discard milk from infected cows
• Colostrum provides very little protection - early nasal colonization

Mycoplasma bovis - mastitis

Clinical signs:

• Agalactia affecting all 4 quarters
• Udder swelling
• Gradual recovery
• Morbidity < 30%
• Mortality/cull rate < 80% of affected cows
• Frequently seen in herd expansions
• Heifers have greatest risk

Mycoplasma bovis diagnosis:

Diagnosis at Newport Labs or Dx Labs

• Isolation/Identification the Mycoplasma
• Immunohistochemistry (IHC)
  • Lung
• Further Identification as M. bovis
  • Polymerase Chain Reaction (PCR)
  • Indirect Fluorescent Antibody (IFA)
• Strain differentiation
  • PCR and AFLP fingerprint

AFLP (Amplified Fragment Length Polymorphism)

• If > 70% same bacterial species
• If < 70% a different bacterial classification except in M. bovis due to strain variation
• Takes a segment of DNA and amplifies this and then sequences this to determine strain

What turns Mycoplasma into a disease... it is everywhere?!?

• NO ONE KNOWS!!!
• The scientific community doesn't fully understand the mechanisms by which this bug goes from an organism of normal flora to one that produces such dramatic, contagious, and costly disease