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3. Food Animal > Udder 2 > Flashcards

Udder 2 Flashcards

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1
Q

methods for detection of clinical mastitis

A
  • Fore stripping
  • Observation of udder
  • Electrical conductivity of milk (automated)
  • Bulk tank filter sock
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2
Q

methods for detection of subclinical mastitis

A
  • CMT
  • DHI individual cow monthly SCC
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3
Q

Mastitis bacteriology; how to collect sample

A
  • Aseptic technique
    > Prep teats as for milking
    > Scrub teat ends with alcohol
    > Careful handling of vials
  • Immediately chill samples
  • Submit fresh within 24 h chilled
  • Otherwise freeze
  • Label with permanent marker
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4
Q

Mastitis bacteriology; how to grow bacteria? what do Sn and Sp depend on?

A
  • Streaking of 0.01 ml (or 0.1 ml) on blood agar and/or selective media for 24 (to 48) h
  • Sensitivity and specificity depend
    on:
  • Sampling technique
  • Sample handling
  • Organism
  • Lab techniques (e.g. enrichment; re- plate)
  • Lab interpretation
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5
Q

mastitis treatment? technique?

A

generally, Intra-mammary (IMM) antibiotic
> “Partial insertion” method – less chance of trauma to teat

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6
Q

What is the objectives of mastitis treatment? pros and cons for different objectives?

A
  • Get the cow back in the tank? [“Clinical cure” – based on appearance of milk]
  • Maximize saleable milk
    > Long term vs. short term
  • Kill bacteria? [“Bacteriologic cure” – based on culture before and >= 1 time 1 to 4 weeks after treatment]
    > Hasten clinical cure?
    > Prevent relapses?
    > Prevent transmission to another cow?
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7
Q

mastitis cure depends on:

A

Microorganism
* Susceptibility to/access by antimicrobials

Cow
* Immune function
* Teat health; gland damage

  • Treatment
    > Duration
  • Environment / herd
    > Probability of re-infection
  • Diagnostic accuracy
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8
Q

cow factors that influence mastitis cure ability

A
  • Parity
  • SCC
  • Duration of infection
    > scar tissue formation
  • Colony count
  • Number of previous cases of clinical mastitis
  • Number of quarters affected
  • For all these variables, higher/more is associated with worse prognosis for bacteriologic cure
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9
Q

Treatment success factors – after cow and pathogen factors

A
  • *** Duration of treatment (8 vs 5 vs 3 vs 2 days)
    > Days or treatments?
  • ** Treatment routes (IMM vs IM)
    • Choice of antibiotics
  • ?? Antimicrobial susceptibility testing (AST)
    > Generally - poor association of AST with clinical or bacteriologic cure
    > With some exceptions (pirlimycin and penicillin/novobiocin for IMM (and newer drugs for BRD)), AST are based on human steady-state plasma [drug], not equal to bovine milk or udder tissue
    > Penicillin resistance (beta-lactamase) useful for Staph. aureus
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10
Q

general antimicrobial pharmacodynamics; what kinds do we have? what is more important for bovine mastitis?

A

time dependent and concentration dependent killers

For bovine mastitis, we want:
* Time-dependent killing
> Time above MIC, not peak concentration, enhances efficacy
> Macrolides, sulfonamides, tetracyclines, beta-lactams, lincosamides

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11
Q

compartment medel for bovine mastitis, and where some common bacteria can be found in thiis model

A

compartments: milk/ducts, tissue, cow/bloodstream

Strep ag: milk/ducts!!!
S. aureus: milk/ducts!, tissue!!!
coliforms: milk/ducts!, cow/bloodstream!!!
Strep sp: milk/ducts!!!, tissue!
Staph sp: milk/ducts!!!, tissue?

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12
Q

keep in mind what fact about quarters when treating mastitis?

A

they are separated by anatomical barriers

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13
Q

Treatment Protocols for Clinical Mastitis Therapy? what is ideal? what is common?

A
  • Options:
    1. No antimicrobial therapy
    2. Treat all cases with IMM antimicrobials
    3. Targeted therapy based on bacterial cause-Ideal
    > Herd historical data-based (educated guess)
    > Individual case culture-based (1 day delay)
  • NB – most cases of mild-moderate clinical mastitis are treated by producers or milkers
    > Protocols developed and monitored by vet > Or not
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14
Q

culture based treatment helps us change our antimicrobial use how?

A

we can reduce antimicrobial use if we identify a gram negative
> coliforms are easily cleared by cow alone, high success

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15
Q

Culture-based treatment decisions; what happens if we delay treatment for culture?

A
  • For mild-moderate clinical mastitis, field study data indicate that delay of start of IMM therapy for 24 h for on-farm culture, with subsequent treatment of only Gram + infections leads to
    > similar herd-level outcomes
    > (e.g. days-out-of-tank; relapse; culling; longer term production)
    as immediate blanket treatment of all cases
  • Typically, gram – and no-growth cases are not treated with antibiotics > 30 to 60% fewer treated cases
  • If cultures are sent out to clinic or lab, delay = 1 to 5 days. No field study data on this
  • Can we write an “educated guess-based protocol”?
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16
Q

IMM mastitis treatments for lactating cow:

A

Lactating cow (therapy)
* Ceftiofur (Spectramast LC; 2 d)
* Cephapirin (Cefa-Lak; 1 d) *Labelled duration of treatment

17
Q

IMM mastitis treatments for dry cow

A

Dry cow (prevention and therapy)
* Ceftiofur (Spectramast DC)
* Cephapirin (Cefa Dri)
* Cloxacillin (Dry Clox)

18
Q

How much do we gain by treating mastitis with intra-mammary antibiotics? how often is there spontaneous bacteriological cure without our help?

A

Spontaneous cure withL
Sta. aureus: 0-11%
Env. strep spp.: 28-30%
CNS: 44-66%
E. coli: 80-95%
Klebsiella spp: 25-60%
no growth: 75-85%

19
Q

How much do we gain by treating mastitis with intra-mammary antibiotics?
- Proportion of treated cases receiving no benefit from antibiotics

A

~67-78%, depending on calculation method

20
Q

Mild-moderate clinical mastitis treatment summary

A
  • Almost all will be dealt with by the producer
  • Should be selective treatment based on cow factors that
    influence the probability of success of treatment
  • Ideally based on culture on-farm or with 1 day turn-around
    > Not practical in many cases
  • Selective use of extended (5 to 8 d) IMM therapy might be more effective than on-label treatment for some pathogens
    > Conflicting data on this
21
Q

what happens to a cows teats in the dry period? what can go wrong, relevant to mastitis?

A
  • Within ~ 2 weeks after dry-off a keratin plug forms in the streak canal to seal the teat
    > ~ 25% of teats fail to close
    > Most new infections occur in these quarters
  • Once involuted, the gland is very resistant to new infection
    > But existing infections, or new IMI acquired in the early dry period frequently become clinical in early lactation
    > 30 to 50% of clinical mastitis in early lactation due to Streptococci and coliforms comes from IMI in the dry period
22
Q

Dry Cow Recommendations for mastitis

A

Objectives:
1. Treat existing infections
2. Prevent new infections in the dry period
3. Prevent clinical mastitis in early lactation

23
Q

not all teats properly close when a cow dries off - what proportion of of new IMI occurs in ‘open’ teats?

A

97% of new IMI occurs in ‘open’ teats

24
Q

incidence of new infections during lactation and the dry period, over time
>when do clinical mastitis cases peak? when are these infections acquired?

A

-vast majority of new infections acquired right after drying off
-2nd peak at the beginning of lactation

> Clinical mastitis peak incidence is typically in early lactation, but many of these cases may be from IMI that occurred in the dry period

25
Q

Expected cure from antibiotic dry cow therapy

A
  • S. aureus: 40-60%
  • S. agalactiae: >95%
  • Env. Streptococci: 70%
  • Coagulase Negative Staph: 70%
  • Coliforms: almost all resolve spontaneously
26
Q

what is dry cow therapy? how do we give it and what is the purpose?

A

Antibiotic
* Long-acting formations (~ 2 weeks)
* Objectives:
> Eliminate existing infections
> Prevent new IMI during involution

Teat sealant
* Inert physical barrier in the teat end
* Objective: prevent new IMI throughout the dry period

27
Q

traditional reccomendation for antibiotic dry cow therapy? which cows, which quarters? what about selective? when would we use this approach and why?

A
  • Traditional recommendation: all quarters, all cows
  • Many quarters/cows don’t have IMI at dry-off
  • Selective dry cow therapy = no antibiotic (but internal teat sealant) for cows (usually not quarters)
  • Low SCC herds (< 250,000 annual)
  • Cows with >1 of
    > Negative culture or CMT near dry-off
    > Low SCC at dry-off +/- throughout lactation > No clinical mastitis in the lactation
  • Can reduce antimicrobial use without short-term harm to udder health
    > Increased therapeutic use in subsequent lactation?
28
Q

Contagious mastitis: what is the reservoir? what are the major agents?

A
  • Reservoir = cow’s udder; transmitted cow to cow
    Major agents:
  • Streptococcus agalactiae
  • Staphylococcus aureus
  • Mycoplasma bovis

> all gram positive

3. Food Animal (22 decks)

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