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Y3 Infectious diseases > Mastitis pathogens > Flashcards

Mastitis pathogens Flashcards

1
Q

What is mastitis?

A

Inflammation of the udder

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2
Q

The level of what is measured to show infection levels?

A

Somatic cell counts

- Increase in SCC reflects the raise in neutrophils which indicates the presence of infection

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3
Q

What are the two types of mastitis?

A

Clinical and sub-clinical

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4
Q

Describe subclinical mastitis

A

Infection present but no visible clinical signs

Changes in somatic cell counts, milk quality and milk yield

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5
Q

What are the different grades of clinical mastitis, describe them

A

Grade 1 - mild milk changes
Grade 2A - acute, changes in milk, udder hot, painful
Grade 2C - Chronic, changes in milk, udder hard and lumpy
Grade 3 - Changes in milk and udder, cow is sick

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6
Q

How do contagious pathogens spread and cause mastitis?

A

From other infected cows

- during milking via fomites (clusters, milker’s hands, communal teat cloths, teat brushes)

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7
Q

When is the key risk period for environmental pathogens to infect cows?

A

Just as cows are coming in to be milked when the canal opens (in response to the tangible signals the cow picks up …time of day, sound of the parlour, being rounded up), and after milking for around half an hour (the time taken for the sphincter to close after being milked)

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8
Q

Name the two main environmental pathogenic causes of mastitis

A

Streptococcus uberis

Coliforms e.g. Escherichia coli

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9
Q

Give 4 examples of contagious pathogens that cause mastitis

A
  • Staphylococcus aureus
  • Streptococcus dysgalactaie
  • Streptococcus agalactiae
  • Mycoplasma spp
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10
Q

Describe how you culture bacteria for identification

A
  • Grow the bacteria
  • Bacteria must be alive
  • No antibiotics for at least 7 days prior to culture
  • Must be shedding on the day of sampling (luck!).
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11
Q

How do you use a PCR to detect pathogens causing mastitis?

A
  • Detects bacterial DNA
  • Dead/alive
  • Before/during/after antibiotics
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12
Q

What are some reasons a sample to identify bacteria might fail?

A
  • Contamination
  • Testing panel
  • Not shedding
  • Poor storage/handling
  • Unknown pathogen
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13
Q

Name the most common contagious mastitis pathogen

A

Staphylococcus aureus

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14
Q

How would Staphylococcus aureus appear on blood agar?

A

White colonies with rings of haemolysis

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15
Q

What are the sources of infection of Staphylococcus aureus?

A

Cows and fomites
Fly spread
Spread among heifers pre-calving by teat sucking

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16
Q

Which features of Staphylococcus aureus make it difficult to treat?

A
  • Intracellular
  • Survives in biofilms
  • Damages the duct system which leads to abscesses
  • Antibiotics are poorly accessible
  • Often responsible for recurrent/chronic infections
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17
Q

Describe the main features of clinical grade 3 mastitis

A
  • Usually newly calved cow (periparurient immunosuppression)
  • Peracute toxaemic sick cow (massive release of a toxin)
  • Gangrene of udder tissue, udder cold, blue, then necrotic and finally sloughs
  • Milk often dark red and bloody
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18
Q

Why is the shedding pattern of Staph.aureus important?

A

Every 5-6 days the levels of bacteria rise are are detectable, between these periods the animal will appear negative as the animal is not shedding

19
Q

Give some control methods for Staph.aureus

A
  • Prevent introduction of infection, check any new cows cell count and examine udder
  • Reduce existing infection in the herd by treating cases and culling chronic cases
  • Dry cow therapy
  • Prevent spread within the herd, most importantly the milking parlor
20
Q

How can spread within the milking parlour be controlled?

A
  • Wear Gloves
  • No common udder cloths/ wipes
  • Early detection and treatment
  • Post milking teat disinfection
  • Milking order
21
Q

How does Streptococcus agalactiae appear on blood agar?

A

Very small, pin prick colonies

Non-haemolytic

22
Q

Describe some of the features of Streptococcus agalactiae and its spread

A

Gram +ve cocci
Contagious
Not associated with persistent infections
Controlled by good parlour hygiene

23
Q

Small pin prick colonies form on which type of agar medium for Streptococcus dysgalactiae?

A

Edwards medium

24
Q

What are the two species of Mycoplasma that cause mastitis?

A

Mycoplasma bovis

Mycoplasma californicum

25
Q

Describe the features of an M.bovis infection

A

Infertility, metritis, otitis media, arthritis, keratoconjunctivitis, pneumonia

26
Q

What is the treatment of cows with Mycoplasma infections?

A

Must be culled

27
Q

Why can you not treat mycoplasma spp with antibiotics?

A

Lack a cell wall therefore non-responsive to beta-lactam antibiotics (penicillins and cephalosporins)

28
Q

Describe the aetiology of mastitis caused by Mycoplasma spp

A

Lipoprotein on outer surface -> stimulates host immunity -> alveolar epithelium degenerates -> massive leucocyte outpouring -> abscesses, alveolar hypertrophy, fibroplasias around ducts -> destroyed quarter

29
Q

How does Escherichia coli appear on blood agar?

A

Creamy white colonies

30
Q

Describe the main features of the E.coli pathogen

A

Gram -ve rods

Source = bovine faeces

31
Q

Which cows are most at risk of an E.coli infection?

A

Those that are housed

32
Q

Describe the pathogenesis of mastitis caused by E.coli

A
  • Contamination of teat end is followed by invasion of teat canal
  • Proliferates rapidly producing LPS endotoxin damages vascular and secretory tissue
  • Clinical outcome of the infection will depend on the quantity and speed of neutrophil influx
33
Q

Describe grade 1 and 2A of E.coli mastitis clinical disease

A

Grade 1 = clots in milk, should self-cure

Grade 2 = Clots in milk, hard hot painful quarter

34
Q

Describe grade 3 of clinical mastitis caused by E.coli

A
  • Very sick cow, endotoxemia shock (usually post calving peri-parturient immunosuppression) udder variable can be cold or hot, hard or soft
  • Milk varies from clots to blood
  • Common
35
Q

How can E.coli infections be controlled?

A
  • Infection particularly common in dry period and early lactation
  • Pre-milking teat preparation: remove the muck
  • Dry cow therapy
  • Vaccination
36
Q

Describe the vaccination of cows against E.coli

A

“Startvac”

  • Give to each cow every few months
  • Will not eliminate disease
  • Reduced severity of clinical disease if having problems with Grade 3 per-acute toxic mastitis
37
Q

Which pathogen has both environmental and contagious strains?

A

Staphylococcus uberis

38
Q

What is the source of Staphylococcus uberis ?

A

Bovine faeces
• Straw yard housing
• Straw bedded cubicles
• Muddy fields at end of summer / crowded shade

39
Q

Describe the pathogenesis of Staphylococcus uberis

A
  • Intracellular in mammary epithelial cells so avoid detection by the immune system
  • Hyaluronic acid capsule : protective shell prevents attachment of antibodies or the neutrophils
  • After phagocytosis some strains can resist killing by neutrophils
40
Q

How can Staphylococcus uberis be controlled?

A
  • Pre-milking teat preparation
  • Milking order
  • Cull chronic cases
  • Dry Cow Therapy
41
Q

Which cows are affected by summer mastitis?

A

• Typically affects DRY cows and HEIFERS OUTDOORS IN SUMMER in fields but is also seen occasionally in steers and bulls and can occur in housed cows in winter

42
Q

What is the vector of summer mastitis?

A

Hydrotea irritans the sheep head fly

43
Q

What are the clinical signs of summer mastitis?

A

Classically hot hard swollen very painful udder with a thick purulent secretion. The cow may also be lame and systemically ill

44
Q

Describe the milking order to minimise transmission

A
  • 1st parity heifers first
  • Healthy cows next (SCC low)
  • High SCC cows
  • Cows with clinical mastitis

Y3 Infectious diseases (19 decks)

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