Mastitis in cattlw

Question 1

Which pathogens may cause mastitis via haematogenous spread

Answer 1

Brucella, TB

Question 2

What are the most common pathogens causing mastitis

Answer 2

Staphs, streps, E coli

Question 3

Which pathogens causing mastitis are most likely due to iatrogenic introduction

Answer 3

Cryptococcus and atypical mycobacterium

Question 4

3 streps that most commonly cause mastitis

Answer 4

Strep dysgalactiae
Strep agalactiae
Strep uberis

Question 5

Which bacteria is an OBLIGATE udder bacterium

Answer 5

Strep agalactiae
-> Means that infection usually permanent once acquired

Question 6

Pathogenesis of strep agalactiae

Answer 6

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

Question 7

Histology of strep agalactiae mastitis

Answer 7

Oedema and neutrophil infiltration
- Vacuolated epithelium with macrophages/fibroblasts

+ clinically udder is painful due to retained secretion

Question 8

Key difference in histology between strep agalactiae and staph mastitis

Answer 8

Strep = mainly in duct space
Staph = mainly in tissue

Question 9

Pathogenesis of staph mastitis

Answer 9

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

Question 10

More chronic form of staph mastitis pathogenesis

Answer 10

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

Question 11

Coliform mastitis pathogenesis

Answer 11

Infection relates to ENVIRONMENTAL EXPOSURE

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

Inflammation centred on ducts

Question 12

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

Answer 12

Coliform mastitis; more severe in these circumstances

Question 13

Causative agent of summer mastitis

Answer 13

Trueperella pyogenes

Question 14

Pathogenesis of summer mastitis

Answer 14

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

Question 15

How does mycoplasma mastitis work

Answer 15

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

Question 16

What is different about infection route in mastitis from TB

Answer 16

Blood borne infection; haematogenous spread

Question 17

Development of tuberculosis mastitis

Answer 17

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

Question 18

What does a cryptococcus mastitis gland look like

Answer 18

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

Question 19

What is the most common cause of mastitis

Answer 19

Streb uberis

Question 20

Two broad classification of mastitis

Answer 20

Contagious: reservoir is on the animal
Environmental

Question 21

5 point mastitis control plan

Answer 21

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

Question 22

Grading mastitis 1-3

Answer 22

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

Question 23

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

Answer 23

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

Question 24

Treatment approach towards gram +ve vs -ve mastitis

Answer 24

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

Gram -ve: more likely to self resolve

Question 25

How can we detect subclinical mastitis

Answer 25

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

Question 26

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

Answer 26

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

Question 27

What is the legal SCC limit for bulk milk

Answer 27

400,000/ml

Question 28

Minor factors affecting SCC counts in milk

Answer 28

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

Question 29

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

Answer 29

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

Question 30

How does California mastitis test work

Answer 30

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

Question 31

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

Answer 31

500,000 NB: often source of bacteria is from milking plant or teat contamination rather than from mastitis

Question 32

Hygeine scoring cattle scale

Answer 32

1-4 where 1 is clean

Question 33

How does milk letdown work in cows

Answer 33

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

Question 34

At what flow rates is risk of mastitis highest

Answer 34

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

Question 35

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

Answer 35

Because otherwise get biphasic milk flow i.e flow from cisterna; then delay before let down This causes LOW FLOW RATES

Question 36

How long does it take most cows to milk out

Answer 36

5-7 mins

Question 37

WHy is post milking disinfection important

Answer 37

Because streak canal stays open for an hour after milking

Question 38

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

Answer 38

20-30 mins

Question 39

What causes hyperkeratosis of teat ends

Answer 39

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

Question 40

Clinical vs bacteriological cure for mastitis

Answer 40

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

Question 41

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

Answer 41

Staph aureus

Question 42

In which mastitis type are we mainly targeting the cow systemically

Answer 42

Coliform

Question 43

Which species are intramammary antibiotics useful for

Answer 43

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

Question 44

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

Answer 44

Strep uberis

Question 45

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

Answer 45

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

Question 46

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

Answer 46

With painful mastitis Because contraction of myoepithelial cells in painful

Question 47

What should we reduce milk yields to before drying off

Answer 47

<15 litres

Question 48

How long does involution take; from drying off

Answer 48

2-3 weeks

Question 49

Why is there increased risk of infection at drying off

Answer 49

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

Question 50

What causes horseshoe shaped lesions on cow teat

Answer 50

Pseudocowpox = parapox virus

Question 51

What is black spot

Answer 51

= necrotising infection of teat with fusobacterium necrophorum