Dr. Ron Erskine presented this information for DAIReXNET on Tuesday, February 12, 2013. For more information, please see our archived webinars page at www.extension.org/pages/15830/archived-dairy-cattle-webinars.
Implications for failure of therapy• “Drugs just don’t work the way they use to……” • Antimicrobial resistance ? • Limited drugs for use in dairy cattle ? • Immune stress ? • Higher milk production?
Is AMR in mastitis pathogens emerging?• ‘scientific evidence does not support a widespread, emerging resistance among mastitis pathogens to antibacterial drugs’
AMR in mastitis pathogens emerging ?• Staph aureus• 50 to 60% of S aureus isolates resistant to unprotected β-lactam drugs • Numerous studies • Forty years • No evidence of any change
Is antibacterial resistance in mastitis pathogens emerging? Temporal studies: same laboratory S aureus Strep E. coli Coagulase negative staphMackie, et N/C ---- N/C ----al. 1989 (coliforms)Erskine, et N/C N/C N/C ----al. 2002Makovec Erythromycin N/C Erythromycin Lincomycinand Ruegg, Lincomycin Pirlimycin2003
US National Residue Program -2010• Kidney Inhibition Swab test or Fast Antimicrobial Screen Test• 211,733 Inspector Generated Samples • 7,000 positive samples • 2,043 confirmed violative residues (1,609 animals) 2012 Residue Sampling Plans, USDA FSIS
2010 Inspector-generated Violations900 Beef cows800 Bob veal700 Bulls600 Dairy cows500 Formula fed veal400 Goat300 Heavy calves200 Heifers100 Market hogs Non-formula fed veal 0 Steers
FDA Survey• The long-anticipated drug-residue-sampling survey by the U.S. Food and Drug Administration has begun.• 900 milk samples from dairy farms had a cull dairy cow residue violation• 900 milk samples from dairies at large.• 26 different drugs Dairy Herd Network, Jan 10, 2012
Mastitis……..• Largest cause of antimicrobial drug use in dairy cows
Antibiotics 101 Concentration-dependent inhibition Magnitude above MIC enhances killing • Peak serum > 10 times MIC Time-dependent inhibition Time above MIC, not peak concentration • All labeled drugs for use in lactating dairy cattle
Antibiotics 101Dose intervals- • Holstein calves treated with chloramphenicol 4x more likely to die if treated once per day as opposed to twice per day (Waltner-Toews, Can Vet J, 1986)Duration • 2 days after clinical and microbiological resolution, severe cases: 7-10 days, chronic: may involve months (Giguere, et al. Antimicrobial Therapy in Veterinary Medicine, 4th edition, 2006, pg 113)
Ampicillin Trihydrate (Polyflex) “3 days treatment is usually adequate, but treatment should be continued for 48 to 72 hours after the animal has become afebrile (up to 7 days)”
Is extended therapy right for you?Depends on the herd
Concentration Milk: Drug PlasmaCeftiofur <1%Sulfadimethoxine 18%Penicillin 19%Ampicillin 27%Spectinomycin 75%Tetracycline 140%Tylosin 250%Lincomycin 450%Erythromycin 650%Adapted from Langston, Antimicrobial Use in Food Animals, in Howard &Smith ed., Current Veterinary Therapy food animal practice, IV.
MILD CLINICAL MASTITIS CultureCHRONIC ??? Gram Yeast, Pseudomonas, etc Coliforms Positive No organism isolated ???? Administer IMM antibioticsNo antibiotictreatment Records
Culture based therapy• 3,500 cow dairy - MI (Hess et al, 2003) • Reduced days withheld by 80% • Two full time veterinarians • Laboratory• 4 herd study - SD and MI (Wagner, et al, 2007) • Bacteriology skills highly variable among herds• 8 herd study - MN, WI, ON ( Lago et el, JDS, 2011) • Reduced antibiotic use 50%
Culture Based Therapy Effects on lactation Immediate Therapy Culture BasedBacteriologic cure* 71 % 60%Milk discard days* 5.9 5.2Herd removal 28% 32%Days at removal 160 137Relapse of clinical 35 % 43 %mastitisDays at relapse 78 82LSCC 4.2 4.4 * 21 days Lago, et al JDS, 2011
SEVERE CLINICAL MASTITISFluidsAnti-Inflammatory CultureIMM and Systemic antibioticsColiforms Gram PositiveContinue antibiotics Continue IMM antibioticsSupportive care Unusual Pathogens (e.g., Pseudomonas, Prototheca) No antibiotics, Supportive care