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Cattle > Mastitis in cattlw > Flashcards

Mastitis in cattlw Flashcards

1
Q

Which pathogens may cause mastitis via haematogenous spread

A

Brucella, TB

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2
Q

What are the most common pathogens causing mastitis

A

Staphs, streps, E coli

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3
Q

Which pathogens causing mastitis are most likely due to iatrogenic introduction

A

Cryptococcus and atypical mycobacterium

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4
Q

3 streps that most commonly cause mastitis

A

Strep dysgalactiae
Strep agalactiae
Strep uberis

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5
Q

Which bacteria is an OBLIGATE udder bacterium

A

Strep agalactiae
-> Means that infection usually permanent once acquired

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6
Q

Pathogenesis of strep agalactiae

A

Obligate bacteria of udder
- Not very invasive; get periods of flare ups with patchy penetration through epithelium then quiescence

Over time: repeated invasion/inflammation leads to fibrosis and involution
NB: mainly see this in older cows due to build up over time

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7
Q

Histology of strep agalactiae mastitis

A

Oedema and neutrophil infiltration
- Vacuolated epithelium with macrophages/fibroblasts

+ clinically udder is painful due to retained secretion

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8
Q

Key difference in histology between strep agalactiae and staph mastitis

A

Strep = mainly in duct space
Staph = mainly in tissue

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9
Q

Pathogenesis of staph mastitis

A

Usually catalase +ve and haemolytic staphs
> More damage to glandular tissue so MORE SEVERE

Common after parturition
> Get necrosis and gangrene of quarter; eventually sloughs

Can get toxaemia if peracute

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10
Q

More chronic form of staph mastitis pathogenesis

A

Organisms invade through epithelium and infect interstitium (go deeper than streps)
- Get foci of infection with granulamtous response and necrotic centre
–> These get walled off via fibrosis

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11
Q

Coliform mastitis pathogenesis

A

Infection relates to ENVIRONMENTAL EXPOSURE

> Often acute and can get septicaemia esp with E coli as more invasive

Inflammation centred on ducts

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12
Q

What type of mastitis do we see in farms that have eliminated classic forms

A

Coliform mastitis; more severe in these circumstances

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13
Q

Causative agent of summer mastitis

A

Trueperella pyogenes

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14
Q

Pathogenesis of summer mastitis

A

Affects non-lactating/immature glands
= Necrotising, suppurative condition in TEAT CANAL
Caused by T pyogenes; likely spread by flies

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15
Q

How does mycoplasma mastitis work

A

Sudden onset agalactiae
Udder is firm and hard but painless
Secretion looks normal BUT get separation when standing

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16
Q

What is different about infection route in mastitis from TB

A

Blood borne infection; haematogenous spread

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17
Q

Development of tuberculosis mastitis

A

= insidious
Progressive increase in size and firmness of gland
Milk appears normal for a long time

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18
Q

What does a cryptococcus mastitis gland look like

A

Firm, grey with haemorrhagic foci and shiny cut surface
Lots of liquefactive necrosis

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19
Q

What is the most common cause of mastitis

A

Streb uberis

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20
Q

Two broad classification of mastitis

A

Contagious: reservoir is on the animal
Environmental

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21
Q

5 point mastitis control plan

A

Regular milking machine maintenance
Post milking teat disinfection
Routine dry cow therapy
Prompt treatment of clinical cases
Culling cows with chronic mastitis

22
Q

Grading mastitis 1-3

A

1: changes to secretion only
2: changes to both secretion and udder
(A = acute; C = chronic)
3: systemically ill cow with changes to secretino and udder

23
Q

What does a water secretion vs clotted secretion suggest about nature of organism causing mastitis

A

Watery = coliform
Clots = gram +ve (streps and staphs)

24
Q

Treatment approach towards gram +ve vs -ve mastitis

A

Gram +ve: more likely to cause persistent infection so want extended Ab course

Gram -ve: more likely to self resolve

25
Q

How can we detect subclinical mastitis

A

Using somatic cell counts
California milk test: to work out which quarters are affected on a specific animal

26
Q

What SCC levels do we consider to be infected or uninfected for individual cow

A

<200,000/ml = uninfected
>200,000/ml = infected

27
Q

What is the legal SCC limit for bulk milk

A

400,000/ml

28
Q

Minor factors affecting SCC counts in milk

A

Age, stage of lactation (low in middle), season, breed, milking fraction (first part is higher)

29
Q

Why must we be careful about interpreting a single SCC reading as meaning subclinical mastitis

A

May be an already cleared TRANSIENT infection; SCC counts remain high for 1 month after clearance

30
Q

How does California mastitis test work

A

Mix milk and detergent
- If there are neutrophils present, get broken down by the detergent which causes jelly mixture
- Graded: negative, trace, 1, 2 and 3

31
Q

What is the legal limit on bactoscan detection of bacteria in milk

A

500,000

NB: often source of bacteria is from milking plant or teat contamination rather than from mastitis

32
Q

Hygeine scoring cattle scale

A

1-4 where 1 is clean

33
Q

How does milk letdown work in cows

A

Teats are stimulated –> oxytocin release –> stimulates letdown by myoepithelial cells contraction (NB: 80% milk is in alveoli and only 20% in milk cistern)

34
Q

At what flow rates is risk of mastitis highest

A

Low flow rates
i.e start and end; END most important because don’t get large flushing flow of milk afterwards

35
Q

Why do we need to do pre-stimulation of teats before milking

A

Because otherwise get biphasic milk flow
i.e flow from cisterna; then delay before let down

This causes LOW FLOW RATES

36
Q

How long does it take most cows to milk out

A

5-7 mins

37
Q

WHy is post milking disinfection important

A

Because streak canal stays open for an hour after milking

38
Q

When should we expect teat orifice to be closed after milking finishes

A

20-30 mins

39
Q

What causes hyperkeratosis of teat ends

A

Over milking or very slow milking
Increases mastitis risk because hard to clean
- Consider herd has issue if >20% teats rough or >10% are very rough

40
Q

Clinical vs bacteriological cure for mastitis

A

Clinical = not eliminated BUT can sell milk
Bacteriological cure= have gotten rid of causative agent

41
Q

In which mastitis type are we mainly targetting marenchyma (vs milk and ducts)

A

Staph aureus

42
Q

In which mastitis type are we mainly targeting the cow systemically

A

Coliform

43
Q

Which species are intramammary antibiotics useful for

A

Non-invasive ones
- Strep agalactiae and dysgalactiae
- coagulase -ve staphs (i.e NOT staph aureus)

44
Q

In which organism mastitis are we likely to need pulse therapy to cure

A

Strep uberis

45
Q

When do we want to use parenteral antibiotics as well as intramammary for mastitis

A

With grade 2 mastitis
> Deeper tissue of gland involved
> With invasive pathogens e.g staph aureus, strep uberis

46
Q

When do we want to avoid using ocytocin as an adjunct to mastitis treatment

A

With painful mastitis
Because contraction of myoepithelial cells in painful

47
Q

What should we reduce milk yields to before drying off

A

<15 litres

48
Q

How long does involution take; from drying off

A

2-3 weeks

49
Q

Why is there increased risk of infection at drying off

A

No flushing of bacteria teat with milk
Increased intramammary pressure can compromise the streak canl

50
Q

What causes horseshoe shaped lesions on cow teat

A

Pseudocowpox = parapox virus

51
Q

What is black spot

A

= necrotising infection of teat with fusobacterium necrophorum

Cattle (20 decks)

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