Question

Summer mastitis in dairy animals is caused by
A. Streptococcus agalactiae
B. Staphylococcus aureus
C. Corynebacterium pyogenes
D. Hydroteae irritans
Choose the correct answer from the options given below:

• A. A, and B only
• B. B and C only
• C. C and D only
• D. A and D only

Hint:

Summer mastitis is historically known as "dry cow mastitis," with Trueperella (Corynebacterium) pyogenes as the primary culprit and the fly Hydrotaea irritans as the key vector.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Summer mastitis is a specific form of acute, suppurative mastitis occurring in dry cows and heifers, typically during the warm summer months.
It has a distinct etiology involving specific synergistic pathogens and insect vectors.

Step 2: Detailed Explanation:
Let us examine the causative agents associated with summer mastitis:
- C. Corynebacterium pyogenes (now reclassified as Trueperella pyogenes): This bacterium is the primary pathogen responsible for summer mastitis, producing a thick, purulent, and foul-smelling secretion in the affected quarter. (True)
- D. Hydrotaea irritans (spelled Hydroteae in the question): This is the sheep headfly, which acts as the major insect vector.
It feeds on teat secretions, especially during summer, and transmits the bacteria from animal to animal. (True)
- A. Streptococcus agalactiae and B. Staphylococcus aureus are major causes of chronic and acute contagious mastitis in lactating herds, but they are not the specific primary agents associated with the "summer mastitis" complex.
Therefore, summer mastitis is caused by the synergistic infection of Corynebacterium pyogenes, transmitted by Hydrotaea irritans, represented by C and D only.

Step 3: Final Answer
The correct option is (C).