Therapeutics (Yr 4) Flashcards
do mastitis cases self cure?
depends on type of bacteria - gram negative organisms can
how long is a traditional dry period?
60 days (can be as low as 40)
why does the duration of activity of dry cow therapies differ?
formulation and base of product
what is the point of dry cow therapy?
clear persistent infections (sub-clinical, intracellular, high cell count)
protect against new infections (infections postpartum, summer mastitis)
what mastitis pathogen survives intracellularly?
Staphylococcus aureus
what bacteria are involved in summer mastitis?
Arcanobacter pyogenes (necrosis)
Peptococcus indolicus (foul smell)
Streptococcus dysgalactia
are there any disadvantages of dry cow therapy?
cell counts too low (possible risk of toxic mastitis)
risk of introducing new infections during applications
possible antibiotic resistance
what is the substance used at teat sealant?
bismuth subnitrate
what does the teat sealant ubroseal blue contain?
bismuth substrate and a blue dye (so you can tell if it has been fully stripped out)
how can you decide the cows for selective dry cow therapy?
bacteriology
SCC
California milk test to check for no infection since milk recording
check for teat end damage
why is bacteriology not good for selecting cows for dry cow therapy?
expensive
Staphylococcus aureus is intermittently shed
what is the cut off used for SCC when selecting for dry cow therapy?
<200 000 cell/ml
(<125 000 cell/ml in lactation heifers)
what is the problem of not fully stripping out sealant when milking?
bismuth substrate reacts with hydrogen sulphide in maturing cheese to create a black spot
what is the protocol for intra-mammary tube application?
after milking and cleaning parlour
clean gloves/wash between cows
pre-dip and allow 30 seconds kill time
surgical spirit and cotton wool until clean
post dip afterwards
allow loafing before going to bedding
recheck daily (reduce feed to reduce milk)
what are the long acting intra-mammary tubes called?
…. xtra
what are cloxacillin +/- ampicillin dry cow tubes aimed at treating?
Staphylococcus aureus (then broaden)
what are the main types of dry cow antibiotic tube?
cloxacillin
penicillin
cephalosporins
what is added to the penicillin dry cow tubes?
framycetin, penethamate
what is framycetin?
active part of neomycin, which has gram negative effects
what is penethamate used for in dry cow antibiotic tubes?
penicillin ester that gets into cells to attack Streptococcus uberus or Staphylococcus aureus
what is required to use cefquinome based dry cow tubes?
culture and sensitivity (it is a CIA)
how long is the milk withhold for dry cow tubes after calving?
about 96 hours (some 156)
how effective is tylosin and tilmicosin as a dry cow therapy?
research suggests efficiency is poor
why may mastitis treatments fail?
antibiotic resistance
bacterial dormancy
L-forms (insensitive to beta-lactams as don’t have a cell wall at this stage)
biofilms
reduced host response (steroid, stress…)
reduced phagocytosis (consequence of some antibiotics)
re-infections from external source, teat-canal infections, uncleared udder
why may antibiotics not reach the site of infection in adequate concentrations?
too low dose
too long dose interval
too short treatment period
what are the pharmokinetic limitations that could lead to mastitis treatment failures?
absorption, disposition, elimination
sequestration due to ionisation
diffusion barriers (oedema, abscesses, fibrosis)
poor delivery across blood/milk barrier in systemic treatment
if antibiotic binds to milk/serum
intracellular pathogens
should fluroquinolones be used for mastitis?
no (shouldn’t be used)
