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Agricultural Animals > Mastitis in Dairy Cattle > Flashcards

Mastitis in Dairy Cattle Flashcards

1
Q

What’s mastitis?

A

aka intrammamary infection (IMI)

caused by ascending bacterial infection

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2
Q

First line of defense against IMI?

A

teat canal
it’s closed by sphincter smooth muscle
open during milking, takes 30 minutes to close so keep it clean during this time

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3
Q

another physcial defense against IMI besides closed teat canal?

A

Keratin plug forms b/w milking
adsorbs bacteria
and antibacterial

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4
Q

Second line of defense against IMI?

A

Somatic cells:
Leukocytes
macrophages - normally found
neutrophils - found w/ infection

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5
Q

What SCC indicates infection?

A

> or equal to 200,000

if no signs: subclinical infection

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6
Q

Clinical IMI signs

A

abnormal milk (flakes, clots, watery)
+/- gland swelling
+/- abnormal cow

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7
Q

Sublinical IMI signs

A

None

SCC > or = 200,000

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8
Q

how to classify IMI severity?

A 
Grade 1 (mild) - abnormal milk
Grade 2 (mod) - abnormal milk & gland 
Grade 3 (sevre) - abnormal milk/gland/cow
90% are Grade 1 or 2
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9
Q

Gangrenous Mastitis
incidence?
pathophys?
etiology?

A

occurs sporadically
bacterial toxin causes vasoconstriction > ischemic necrosis
small ruminants: Staphylococcus aureus
cattle: E.coli

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10
Q

Common IMI pathogens?

A 
Gram neg/coliform/environmental
     E. coli
     Klebsiella
Gram positive
     Staphylococcus aureus
     Streptococcus agalactiae
     Environmental streps

Mycoplasma bovis (doesn’t stain)

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11
Q

How to treat IMI?

A

G positives: intramammary antibiotics

G negatives: neuts will take care of it

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12
Q

IMI disease severity?

A 
Gram positives
    cause chronic, subclinical infection
Gram negatives
     most not severe
     can cause severe IMI
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13
Q

IMI px?

A

Severity of gram negative disease reduced with “core-antigen” vaccine

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14
Q

IMI pathogen reservoirs?

A 
contagious (mammary gland)
spread during milking or cross suckling
     staph aureus
     strep. agalactiae
     M. bovis - most common contagious
environmental (housing/bedding)
      gram neg's - E.coli most common G-
      environmental streps
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15
Q

Milking parlor goals

A

efficiently milk clean, dry teats

prevent spread of milk from cow to cow

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16
Q

Milk parlor steps

A 
forestrip milk from each quarter
pre-milking teat dip
dry teats
attach milking unit
detach
post-milking teat dip
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17
Q

What’s forestripping?

A

take 2-3 strips of milk from each quarter to look for abnormalities (flakes, clots, watery)

stimulates milk letdown results in faster milking

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18
Q

pre-milking teat dip?

A

dip in 0.5% iodine (disinfectant)

controls environmental mastitis

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19
Q

drying teats step?

A

ONE TOWEL PER COW

to prevent spreading

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20
Q

post-milking teat dip?

A

dip in 1% iodine
to kill any transferred bacteria
and 10% glycerin (skin conditioner)
to prevent cracking

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21
Q

Key practices to control IMI?

A
  1. reduce milk spread during milking
  2. post-milking teat dip
  3. dry cow (not lactating) antibiotic Tx
  4. separate/cull infected animals
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22
Q

Steps to prevent environmental IMI?

A 
"core antigen" vaccine
CLEAN, DRY bedding
pre-milk teat dip
milk CLEAN, DRY teats
let cows stand 30 minutes after milking
      for teat canal to close
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23
Q

When does infection w/ environmental pathogens occur?

A

occurs 4-5 times more during dry period
before and after calving
not milking so intramammary pressure
builds and opens teat end. Bacteria
more likely to enter into favorable
conditions

dirty straw bedding

during milking: dirty teats

24
Q

What’s the “core antigen” vaccine?

A

used for IMI infections
mutant bacteria w/ exposed LPS core (endotoxin)
reduces severity of signs and clinical
cases

25
Q

Udder health Diagnostics?

A

SCC

Aerobic milk culture and susceptibility testing

26
Q

What do SCC’s tell you?

A

udder health
IMI status
milk quality

27
Q

How does the SCC test work?

A

Can be in lab test or cow side

in lab: machine
cow side: california mastitis test (CMT)

28
Q

what is composite SCC?

A

When milk’s collected from all glands and mixed into 1 sample for testing

29
Q

Factors affecting SCC and interpretation?

A

older animals more likely to have IMI

less specific in small ruminants
test SCC during peak milk production
SCC’s appear higher during early
and late lactation

30
Q

How to interpret SCC’s?

A

multiply reported value by 1,000/ml!

31
Q

How does CMT work?

A

California mastitis test

mix milk w/ detergent, cells lyse and release dna. DNA is viscous, so the more cells there are the more viscous the solution.

cow side test, tests each quarter
identifies subclinical IMI
don’t test abnormal milk b/c then there’s no point, u can already tell!

32
Q

What’s BTSCC?

A

Bulk Tank SCC
Milk from all cows into bulk tank
then measure SCC
gives you average SCC of herd

positively related with IMI prevalence!!!

33
Q

BTSCC legal limits?

A

US: 750,000
CA: 600,000
EU/Aus/NZ: 400,000

majority of our milk meets EU standards

34
Q

relationship b/w herd size and avg SCC?

A

higher in smaller herds

35
Q

When and why should you do milk cultures?

A 
BT cultures
    to MONITOR for pathogens in herd
    Finding S. agalactiae not tolerated
    find infected cows and treat
    M. bovis not tolerated here
     coliform count tells us dirt teats were 
     milked
Individual clinical cow
     to IDENTIFY IMI cause
individual subclinical cow w/ high SCC
    to IDENTIFY IMI cause
36
Q

Tests to ID milk pathogens?

A

Aerobic Milk Culture
Coagulase Test
CAMP Test
Special media for M. bovis

37
Q

Aerobic milk culture test?

A 
plate on Blood agar
    everything grows on this except M. bovis
Then on MacConkey agar
    Selective media, only grows gram neg
    growth means: 
           gram neg present
           and maybe gram pos too, it just
           doesn't grow on MacConkey
38
Q

How to ID:
M. bovis
S. aureus
S. agalactiae

A 
M. bovis - request special media
S. aureus - beta hemolysis on blood agar
        meaning, complete hemolysis
        Positive coagulase test to confirm
S. agalactiae - Positive CAMP test
        S. ag forms the arrow!
39
Q

Why do antibiotic susceptibility test?

A

to exclude antibiotics as possible treatments (when pathogen is resistant)

40
Q

S. aureus characteristics?

A

gram positivie
beta hemolysis
coagulase positive

41
Q

S. aureus infection characteristics?

A

Chronic, subclinical with intermittent clinical episodes

intermittently shed -> fals neg. cultures

42
Q

S. aureus virulence factors

A

Aid in colonization
* surface adhesins
adheres to epidermis
* resistant to keratin plug

Evasion of immune system

  • Protein A prevents phagocytosis
  • Survival in neuts
  • Microabscess formation
43
Q

S. aureus Tx?

A 
Poor Tx efficacy
    * 50% resistant to beta lactam Abx
    * poor microabscess penetration
    * protected w/in neuts from Abx
    * L-forms have no cell wall so beta 
      lactams not effective

bacteriologic cure (eliminating bacteria) less likely as infection duration increases.

44
Q

S. aureus Px?

A

Vaccine unsuccessful

not recommended

45
Q

S. agalactiae characteristics?

A

Gram positive

CAMP positive

46
Q

S. agalactiae infection characteristics?

A

chronic, subclinical

high numbers shed in milk

47
Q

S. agalactiae Tx?

A

Sensitive to beta lactam Ab

48
Q

M. bovis characteristics?

A

No cell wall

special culture required!

49
Q

M. bovis infection characteristics?

A 
uncurable clinical mastitis
disease in calves
affects multiple systems
     mam gland, respiratory, urogenital
spreads to multiple glands

signs in calves
pneumonia, otitis, arthritis

50
Q

M. bovis Tx?

A

No treatment
cull positive cows
if high prevalence, segregate into “Myco pen”

51
Q

Environmental strep characteristics

A

Gram positive

52
Q

Envir. strep. infection characteristics?

A

clinical mastitis

if not treated: chronic, subclinical

53
Q

Envir. strep. Tx?

A

Abx
Dry Tx (intramammary Abx infusion)
if untreated -> chronic, subclinical infection

54
Q

Coliform bacteria characteristics?

A

Gram negative

MacConkey positive

55
Q

Colifrom bacteria infection characteristics?

A

short duration clinical mastitis
resolves w/o Tx
Sometimes severe dz

56
Q

E. coli pathophys

A

rapidly multiplies in milk > e. coli death > endotoxin release > inflammation

signs:
udder firm and swollen, decreased milk production, fever, dec. rumen motility

57
Q

Coliform Tx?

A 
No Tx
not susceptible to Abx
Supportive care
      NSAIDs
      Fluids
Systemic disease Tx
     ceftiofur may help

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