Mastitis in Dairy Cattle Flashcards
What’s mastitis?
aka intrammamary infection (IMI)
caused by ascending bacterial infection
First line of defense against IMI?
teat canal
it’s closed by sphincter smooth muscle
open during milking, takes 30 minutes to close so keep it clean during this time
another physcial defense against IMI besides closed teat canal?
Keratin plug forms b/w milking
adsorbs bacteria
and antibacterial
Second line of defense against IMI?
Somatic cells:
Leukocytes
macrophages - normally found
neutrophils - found w/ infection
What SCC indicates infection?
> or equal to 200,000
if no signs: subclinical infection
Clinical IMI signs
abnormal milk (flakes, clots, watery)
+/- gland swelling
+/- abnormal cow
Sublinical IMI signs
None
SCC > or = 200,000
how to classify IMI severity?
Grade 1 (mild) - abnormal milk Grade 2 (mod) - abnormal milk & gland Grade 3 (sevre) - abnormal milk/gland/cow 90% are Grade 1 or 2
Gangrenous Mastitis
incidence?
pathophys?
etiology?
occurs sporadically
bacterial toxin causes vasoconstriction > ischemic necrosis
small ruminants: Staphylococcus aureus
cattle: E.coli
Common IMI pathogens?
Gram neg/coliform/environmental
E. coli
Klebsiella
Gram positive
Staphylococcus aureus
Streptococcus agalactiae
Environmental streps
Mycoplasma bovis (doesn’t stain)
How to treat IMI?
G positives: intramammary antibiotics
G negatives: neuts will take care of it
IMI disease severity?
Gram positives
cause chronic, subclinical infection
Gram negatives
most not severe
can cause severe IMIIMI px?
Severity of gram negative disease reduced with “core-antigen” vaccine
IMI pathogen reservoirs?
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 strepsMilking parlor goals
efficiently milk clean, dry teats
prevent spread of milk from cow to cow
Milk parlor steps
forestrip milk from each quarter pre-milking teat dip dry teats attach milking unit detach post-milking teat dip
What’s forestripping?
take 2-3 strips of milk from each quarter to look for abnormalities (flakes, clots, watery)
stimulates milk letdown results in faster milking
pre-milking teat dip?
dip in 0.5% iodine (disinfectant)
controls environmental mastitis
drying teats step?
ONE TOWEL PER COW
to prevent spreading
post-milking teat dip?
dip in 1% iodine
to kill any transferred bacteria
and 10% glycerin (skin conditioner)
to prevent cracking
Key practices to control IMI?
- reduce milk spread during milking
- post-milking teat dip
- dry cow (not lactating) antibiotic Tx
- separate/cull infected animals
Steps to prevent environmental IMI?
"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 closeWhen does infection w/ environmental pathogens occur?
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
What’s the “core antigen” vaccine?
used for IMI infections
mutant bacteria w/ exposed LPS core (endotoxin)
reduces severity of signs and clinical
cases
Udder health Diagnostics?
SCC
Aerobic milk culture and susceptibility testing
What do SCC’s tell you?
udder health
IMI status
milk quality
How does the SCC test work?
Can be in lab test or cow side
in lab: machine
cow side: california mastitis test (CMT)
what is composite SCC?
When milk’s collected from all glands and mixed into 1 sample for testing
Factors affecting SCC and interpretation?
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
How to interpret SCC’s?
multiply reported value by 1,000/ml!
How does CMT work?
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!
What’s BTSCC?
Bulk Tank SCC
Milk from all cows into bulk tank
then measure SCC
gives you average SCC of herd
positively related with IMI prevalence!!!
BTSCC legal limits?
US: 750,000
CA: 600,000
EU/Aus/NZ: 400,000
majority of our milk meets EU standards
relationship b/w herd size and avg SCC?
higher in smaller herds
When and why should you do milk cultures?
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 causeTests to ID milk pathogens?
Aerobic Milk Culture
Coagulase Test
CAMP Test
Special media for M. bovis
Aerobic milk culture test?
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 MacConkeyHow to ID:
M. bovis
S. aureus
S. agalactiae
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!Why do antibiotic susceptibility test?
to exclude antibiotics as possible treatments (when pathogen is resistant)
S. aureus characteristics?
gram positivie
beta hemolysis
coagulase positive
S. aureus infection characteristics?
Chronic, subclinical with intermittent clinical episodes
intermittently shed -> fals neg. cultures
S. aureus virulence factors
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
S. aureus Tx?
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.
S. aureus Px?
Vaccine unsuccessful
not recommended
S. agalactiae characteristics?
Gram positive
CAMP positive
S. agalactiae infection characteristics?
chronic, subclinical
high numbers shed in milk
S. agalactiae Tx?
Sensitive to beta lactam Ab
M. bovis characteristics?
No cell wall
special culture required!
M. bovis infection characteristics?
uncurable clinical mastitis
disease in calves
affects multiple systems
mam gland, respiratory, urogenital
spreads to multiple glands
signs in calves
pneumonia, otitis, arthritis
M. bovis Tx?
No treatment
cull positive cows
if high prevalence, segregate into “Myco pen”
Environmental strep characteristics
Gram positive
Envir. strep. infection characteristics?
clinical mastitis
if not treated: chronic, subclinical
Envir. strep. Tx?
Abx
Dry Tx (intramammary Abx infusion)
if untreated -> chronic, subclinical infection
Coliform bacteria characteristics?
Gram negative
MacConkey positive
Colifrom bacteria infection characteristics?
short duration clinical mastitis
resolves w/o Tx
Sometimes severe dz
E. coli pathophys
rapidly multiplies in milk > e. coli death > endotoxin release > inflammation
signs:
udder firm and swollen, decreased milk production, fever, dec. rumen motility
Coliform Tx?
No Tx
not susceptible to Abx
Supportive care
NSAIDs
Fluids
Systemic disease Tx
ceftiofur may help
