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7. Contagious Mastitis

 

Staphylococcus aureus (4)

  1. Can survive inside white blood cells (intracellular).
  2. Intermittently shed from the mammary gland, so milk must be cultured repeatedly to be sure a cow is truly negative.
  3. There is a 75% chance of detection with one culture from an infected cow.
  4. There is a 95% chance of detection with three cultures collected on consecutive days from an infected cow.
  5. In chronic cases, fibrosis and micro-abscess formation in the udder decrease the probability of adequate drug distribution to the site of infection.

 

 

Streptococcus agalactiae (4)

 

  1. Colonizes the epithelial surface of teat ducts.
  2. The udder is the reservoir of infection.
  3. Toxin elaboration results in inflammation.
  4. Organisms are shed in the milk in high numbers.
  5. Antibiotic therapy for lactating cows is highly successful provided the bacteria are not resistant to the antibiotic used.

 

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