Clinical aspects of mammary gland disease

Question 1

WHat are the clinical signs of mastitis?

Answer 1

• clots in milk
• chalky
• milk drop
• watery milk
• hungry calf
• hard/swollen udder
• endotoxic shock
• systemic signs
• pus

Question 2

Sub clinical signs?

Answer 2

• milk cell count

Question 3

Grades of mastitis?

Answer 3

1. change in milk
2. udder hard
3. systemic signs
4. toxic shock

Question 4

How do all infections occur?

Answer 4

• entrance via the teat end
• bacterial - sometimes fungal

Question 5

Describe the skin of the teat/udder

Answer 5

• keratin
• thick squamous ep

Question 6

Describe the teat end and teat canal anatomy

Answer 6

• keratin layer
• interlocking folds
• muscular sphincter
• lymphoid tissue

Question 7

Describe the pathogenesis of mastitis

Answer 7

1. bacterial contamination of teat end
2. bacterial invasion through teat orifice
3. ascending infection
4. adherence of bacteria
5. colonisation of bacteria
6. liberation of endotoxin - only if G-ve bacteria
7. inflammation and immune response
8. milk/ udder changes
9. systemic signs

Question 8

What are the udder defence mechanisms?

Answer 8

• reg milk flow - flushing
• teat canal - keratin lined/ physical barrier
• lactoferrin - bacteriostatic, iron-chelating
• keratin plug - dry period
• commensals - antibiotics, over teating dipping interfers
• sphincter - occludes teat orifice

Question 9

What damage occurs at the end of the teat?

Answer 9

• hyperkeratosis

Question 10

What are the immunological mechanisms of udder defence?

Answer 10

• SCC
  
  • neutrophils
  • leukocytes
  • macrophages
  • CMT

Question 11

Milk and udder changes?

Answer 11

• duct and teat cistern fill with secretions
• casein clots
• serum leakage
• alveoli obliterated
• local involution

Question 12

What are the udder changes?

Answer 12

• haemorrhage
• well demarcated zone of necrosis
• oedema
• abscess

Question 13

What are the major mastitis pathogens (contagious and environmental)?

Answer 13

• contagious (mostly g+ve)
  
  • S.aureus
  • streptococcus agalactiae
  • strep. dysgalactiae
  • mycoplasma (-ve)
  • CNS
• environmental (-ve)
  
  • mainly E.coli
  • strept
  • CNS
• Strepuberis - cow - parlour - cow / enviro - cow

Question 14

WHich type of mastitis is more serious?

Answer 14

• G-ve - so environmental
• have lipopolysacchardes
• grades 3+4

Question 15

Describe the pathogenicity of S.aureus

Answer 15

• contagious
• G+ve
• catalase +ve
• chronic infections
• hides in phagolysosomes
• strong inflam response
• high SCC
• can have gangrenous mastitis as well

Question 16

WHat are the other contagious pathogens?

Answer 16

• S.agalactiae
  
  • +ve
  • highly proliferative
  • major problem
  • very contagious
• S.dysgalactiae
  
  • +ve
  • teat end damage
  • tonsillar carriage
  • part of summer mastitis complex
  • cause in dry cow
• Mycoplasma bovis
  
  • -ve
  • causes arthritis, pneumonia, otitis
  • special culture media, PCR
  • poor response to antibiotics
• CNS
  
  • +ve
  • commensal on teat end
  • minor pathogens
  • high SCC
    ​

Question 17

WHat about Steptococcus uberis?

Answer 17

• +ve
• resistant to phagocyctosis
• summer outbreaks
• cow reservoirs
• grazin/ straw bedding

Question 18

What kind of infection does E.coli produce?

Answer 18

• G-ve
• environmental contamination
• housing associated
• common
• hygiene related
• grades 1-4
• high SCC rare
• more acute and severe infections

Question 19

What are the causes of dry gland mastitis?

Answer 19

• T.pyogenes
• Peptococcus indolicus
• S.dysagalactidae
  
  • summer mastitis matrix
  • purulent discharge
  • spread by flies
  • quartre loss in maiden heifers

Question 20

What about masitis in sheep?

Answer 20

• 80% organisms:
  
  • S.aureus - commensual
  • Manheimia haemolytica
• acute/ gangrenous
• chronic post weaning
• blind teat at lambing