Pathogenesis, pathology and aetiology of mastitis

Question 1

What are the different routes by which microorganisms can enter the mammary gland?

Answer 1

1. Galactogenic route (via teat canal)
2. Haematogenous
3. Percutaneos

Question 2

What is the main route of entry to the udder? And what defences prevent this?

Answer 2

Galactogenic route:

• Teat sphincter
• Keratinized epithelium (see lecture for more)
• Furstenberg’s Rosette

Question 3

What are some of the pathological features of peracute mastits?

Answer 3

Occurs around parturition.

Quater can rapidly progress to moist gangrene and oozes serum. Cow may rapidly die due to toxaemia.

Question 4

What does acute mastitis look like microscopically?

Answer 4

Interstitial oedema and neutrophil infiltration of interstitium and glandular acini.

Question 5

What happens in chronic mastitis?

Answer 5

Acini are obliterated by fibrosis, ducts may become obstructed by polyps. Abscesses may also form. This can result in involution and permanent fibrosis of the mammary gland.

Question 6

Why is there not much point in treating chronic SAU infection?

Answer 6

It leads to the formation of granulomatous structures so antibiotics would not easily get in.

Question 7

What is the progression of subclinical mastitis?

Answer 7

Successive flare ups and repair of tissue by fibrosis can occur. This can lead to involution of the tissue. It will have a similar appearance to a chronic clinical mastitis.

Question 8

What are the primary agents that cause mastitis in the lactation period?

Answer 8

Staph aureas
E. coli
Strep uberis

S. agalctiae
S. dysgalatiae
M. bovis
C. bovis

P. aeruginosa
K. pneumoniae
Yeasts

Question 9

Why is it difficult for the immune system to remove SAU?

Answer 9

I lives in the intracellular space

Question 10

HOw does M. bovis reach the udder?

Answer 10

Possible by haematogenous spread.

Question 11

What are the main agents involved in dry cow mastitis?

Answer 11

• Trueperella pyogenes
• S. dysgalactiae
• Peptostreptococcus indolicus

Question 12

Why is dry cow mastitis so important?

Answer 12

Many lactation infections are due to infection in the dry cow period, therefore DCT can be highly effective in preventing mastitis in subsequent lactation.

Question 13

What are the agents that cause mastitis in ewes?

Answer 13

M. haemolytica
S. aureus
E. coli
Streptococci
M. agalactiae