Mastitis

Question 1

What are three methods that can be used to detect subclinical mastitis in a herd - briefly discuss the pros and cons of each?

Answer 1

1. Somatic cell count (SCC) - threshold for infection > 200 cells/mL
2. California mastitis test (CMT) - 2-3 ml of milk added to a panel and the amount of agglutination that results indicates whether mastitis is present
3. Electrical conductivity - with mastitis there is an increase in sodium and potassium - these improve electrical conductivity through the milk

Question 2

What are the three different types of clinical mastitis that are seen and what are the changes associated with each?

Answer 2

1. Mild clinical mastitis - change in the viscosity, colour or consistency of milk
2. Moderate clinical mastitis - milk is abnormal but gland is swollen red and painful
3. Severe clinical mastitis - as above w/ cow being systemically ill

Question 3

What are the four major contagious pathogens causing mastitis?

Answer 3

• Streptococcus agalactiae and Staphylococcus aureus - major contagious pathogens
• Corynebacterium bovis - minor
• Mycoplasma carried in places other than mammary gland but once it get access it becomes highly contagious

Question 4

How are infectious causes of mastitis diagnosed?

Answer 4

Culture of milk samples

Question 5

Describe three control/prevention strategies that may be implemented for contagious mastitis (with respect to specific organisms):

Answer 5

1. Post dipping in iodide solution → prevent new infections
2. S. agalactiae and C. bovis - intramammary Ab’s are usually sufficient to control existing infections
3. Staphylococcus aureus and Mycoplasma - significantly harder to eradicate (animals are often culled)

Question 6

What are the main environmental mastitis pathogens?

Answer 6

coliforms and environmental streptococci (S. uberis, S. dysgalactiae

Question 7

What are the most frequent bacteria that are isolated from mastitis cows?

Answer 7

Coagulase-negative Staph (S. hyicus, epidermidis) - contagious or environmental pathogens - most commonly isolated from cows

Question 8

Provide two possible control strategies to prevent the incidence of environmental mastitis:

Answer 8

• Frequent manure removal
• Appropriate free stalls + manage the bedding
• Provide pastured cows with areas to lie down
• Predipping teats and dry udders