Udder 2 Flashcards
methods for detection of clinical mastitis
- Fore stripping
- Observation of udder
- Electrical conductivity of milk (automated)
- Bulk tank filter sock
methods for detection of subclinical mastitis
- CMT
- DHI individual cow monthly SCC
Mastitis bacteriology; how to collect sample
- 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
Mastitis bacteriology; how to grow bacteria? what do Sn and Sp depend on?
- 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
mastitis treatment? technique?
generally, Intra-mammary (IMM) antibiotic
> “Partial insertion” method – less chance of trauma to teat
What is the objectives of mastitis treatment? pros and cons for different objectives?
- 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?
mastitis cure depends on:
Microorganism
* Susceptibility to/access by antimicrobials
Cow
* Immune function
* Teat health; gland damage
- Treatment
> Duration - Environment / herd
> Probability of re-infection - Diagnostic accuracy
cow factors that influence mastitis cure ability
- 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
Treatment success factors – after cow and pathogen factors
- *** 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
general antimicrobial pharmacodynamics; what kinds do we have? what is more important for bovine mastitis?
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
compartment medel for bovine mastitis, and where some common bacteria can be found in thiis model
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?
keep in mind what fact about quarters when treating mastitis?
they are separated by anatomical barriers
Treatment Protocols for Clinical Mastitis Therapy? what is ideal? what is common?
- 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
culture based treatment helps us change our antimicrobial use how?
we can reduce antimicrobial use if we identify a gram negative
> coliforms are easily cleared by cow alone, high success
Culture-based treatment decisions; what happens if we delay treatment for culture?
- 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”?
IMM mastitis treatments for lactating cow:
Lactating cow (therapy)
* Ceftiofur (Spectramast LC; 2 d)
* Cephapirin (Cefa-Lak; 1 d) *Labelled duration of treatment
IMM mastitis treatments for dry cow
Dry cow (prevention and therapy)
* Ceftiofur (Spectramast DC)
* Cephapirin (Cefa Dri)
* Cloxacillin (Dry Clox)
How much do we gain by treating mastitis with intra-mammary antibiotics? how often is there spontaneous bacteriological cure without our help?
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%
How much do we gain by treating mastitis with intra-mammary antibiotics?
- Proportion of treated cases receiving no benefit from antibiotics
~67-78%, depending on calculation method
Mild-moderate clinical mastitis treatment summary
- 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
what happens to a cows teats in the dry period? what can go wrong, relevant to mastitis?
- 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
Dry Cow Recommendations for mastitis
Objectives:
1. Treat existing infections
2. Prevent new infections in the dry period
3. Prevent clinical mastitis in early lactation
not all teats properly close when a cow dries off - what proportion of of new IMI occurs in ‘open’ teats?
97% of new IMI occurs in ‘open’ teats
incidence of new infections during lactation and the dry period, over time
>when do clinical mastitis cases peak? when are these infections acquired?
-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
