Risk factors associated with short-term post-treatment outcomes of clinical mastitis.
The objectives of this study were to characterize 60-d outcomes after treatment of mild (abnormal milk) and moderate (abnormal milk and abnormal udder) cases of clinical mastitis (CM) occurring in a single quarter of cows on Wisconsin farms (n=4) and to determine risk factors associated with those outcomes. Duplicate milk samples were collected from the affected quarter of each cow for microbiological analysis at the onset of CM (PRE) and 21 d later (POST). Cows were treated only in the affected quarter using an intramammary product containing 125 mg of ceftiofur. Bacteriological cure was defined as absence of pathogens in the POST sample obtained from the enrolled quarter. Recurrence was defined for the cow when CM occurred after the milk-withholding period for the enrolled case of CM. Retention in the herd was defined when a cow was retained within the herd for the 60-d follow-up period. Somatic cell count reduction (SCCR) was defined at the cow level as somatic cell count (SCC) below 200,000 cells/mL at the Dairy Herd Improvement Association test day occurring between 21 to 55 d post-treatment. The effects of farm, days in milk, parity, severity, microbiological diagnosis at PRE, previous milk yield, previous SCC, previous occurrence of CM and treatment duration on selected post-treatment outcomes were assessed using Chi-squared analysis and logistic regression. Microbiological results at PRE were distributed as: Escherichia coli (n=14), Klebsiella spp. (n=11), Enterobacter spp. (n=8), Serratia spp. (n=7), other gram-negative species (n=3), Streptococcus spp. (n=25), coagulase-negative staphylococci (n=4); Staphylococcus aureus (n=1); Streptococcus agalactiae (n=1), other gram-positive species (n=9), and culture negative (n=60). Treated quarters were more likely to experience bacteriological cure when the cow experienced CM for the first time in the lactation and when no pathogen was recovered from PRE milk samples obtained from the enrolled quarter. Parity and bacteriological cure were associated with the probability of recurrence. Greater milk yield at previous Dairy Herd Improvement test was the most important predictor for retention within the herd. When SCC before CM was >200,000 cells/mL the probability of having SCCR after treatment was decreased. When the case experienced bacteriological cure, the cow was less likely to experience recurrent cases and was more likely to have SCCR below 200,000 cells/mL. Post-treatment outcomes, such as recurrence and SCCR, are strongly associated with bacteriological cure and, when monitored, can be used to help determine if a treatment has been successful. Information about the etiology of CM, history of clinical and subclinical mastitis, and parity are useful to review when making strategic treatment decisions.
Pinzón-Sánchez C
，Ruegg PL
《-》
The selective treatment of clinical mastitis based on on-farm culture results: II. Effects on lactation performance, including clinical mastitis recurrence, somatic cell count, milk production, and cow survival.
The objective of this multi-state, multi-herd clinical trial was to report on the efficacy of using an on-farm culture system to guide strategic treatment decisions in cows with clinical mastitis. The study was conducted in 8 commercial dairy farms ranging in size from 144 to 1,795 cows from Minnesota, Wisconsin, and Ontario, Canada. A total of 422 cows affected with mild or moderate clinical mastitis in 449 quarters were randomly assigned to either (1) a positive-control treatment program or (2) an on-farm culture-based treatment program. Quarter cases assigned to the positive-control group received immediate on-label intramammary treatment with cephapirin sodium. Quarters assigned to the culture-based treatment program were not treated until the results of on-farm culture were determined after 18 to 24h of incubation. Quarters in the culture-based treatment program that had gram-positive growth or a mixed infection were treated according to label instruction using intramammary cephapirin sodium. Quarters assigned to the culture-based treatment program that had gram-negative or no-growth did not receive intramammary therapy. It was already reported in a companion paper that the selective treatment of clinical mastitis based on on-farm culture results decreases antibiotic use by half and tends to decrease milk withholding time without affecting short-term clinical and bacteriological outcomes. The present article reports on long-term outcomes of the aforementioned study. No statistically significant differences existed between cases assigned to the positive-control program and cases assigned to the culture-based treatment program in risk and days for recurrence of clinical mastitis in the same quarter (35% and 78 d vs. 43% and 82 d), linear somatic cell count (4.2 vs. 4.4), daily milk production (30.0 vs. 30.7 kg), and risk and days for culling or death events (28% and 160 d vs. 32% and 137 d) for the rest of the lactation after enrollment of the clinical mastitis case. In summary, the selective treatment of clinical mastitis based on on-farm culture resulted in no differences in long-term outcomes, such as recurrence of clinical mastitis in the same quarter, somatic cell count, milk production, and cow survival for the rest of the lactation after clinical mastitis.
Lago A
，Godden SM
，Bey R
，Ruegg PL
，Leslie K
... -
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Negatively controlled, randomized clinical trial to evaluate intramammary treatment of nonsevere, gram-negative clinical mastitis.
The objective of this negatively controlled, randomized clinical trial was to examine clinical outcomes of 2-d or 8-d treatment using an approved intramammary (IMM) product containing ceftiofur hydrochloride compared with no antimicrobial treatment of nonsevere, gram-negative cases of clinical mastitis (CM). Additionally, we contrasted clinical outcomes of cases caused by Escherichia coli (n = 56) or Klebsiella pneumoniae (n = 54). Cases (n = 168) of nonsevere (abnormal milk or abnormal milk and udder) CM were randomly assigned to receive 2 d (n = 56) or 8 d (n = 56) of IMM ceftiofur or assigned to a negative control group (n = 56). At enrollment, quarter milk samples were collected and used for on-farm culture, somatic cell count (SCC), and confirmatory microbiological analysis. Quarter milk samples were collected weekly from 7 to 28 d after enrollment for microbiological and SCC analysis. Clinical outcomes were followed for 90 d or until the end of lactation (follow-up period, FUP). Overall, no significant differences in quarter-level recurrence of CM (32% for negative control, 34% for the 2-d treatment, and 32% for the 8-d treatment), culling (18% for negative control, 12% for 2-d treatment, and 11% for 8-d treatment), voluntary dry-off of affected quarters (20% for negative control, 30% for 2-d treatment, and 27% for 8-d treatment), days until return to normal milk (4.2 days for negative control, 4.8 days for 2-d treatment, 4.5 days for 8-d treatment), weekly quarter-SCC during the FUP (6.1, 6.3, and 6.0 log10SCC for the negative control, 2-d, and 8-d treatments, respectively), or daily milk yield during the FUP (37.1, 36.3, and 37.6 kg/cow per day for the negative control, 2-d, and 8-d treatments, respectively) were observed among experimental groups. Days of discarded milk were greater for cows assigned to 8-d IMM ceftiofur (11.1 d) than for cows assigned to 2-d (6.9 d) or cows assigned to negative control (5.6 d). Bacteriological cure (BC) at 14 and 21 d after enrollment was greater in cows assigned to 8-d (89%) and 2-d (84%) treatment than in cows assigned to negative control (67%), but this outcome was confounded by pathogen. For CM caused by Kleb. pneumoniae, BC was greater for quarters assigned to receive treatment (combined 2-d and 8-d groups; 74% BC) than for quarters assigned to negative control (18%). In contrast, no differences in BC were observed for CM caused by E. coli (97-98%). Culling and voluntary dry-off of affected quarters were significantly greater for cows with quarters affected by Kleb. pneumoniae (22% culled, 39% voluntary dry-off of quarters) than for cows with quarters affected with E. coli (7% culled, 11% voluntary dry-off of quarters). Overall, use of IMM ceftiofur did not result in improvement of most clinical outcomes, but differences between E. coli and Kleb. pneumoniae were evident. In contrast to E. coli, Kleb. pneumoniae caused chronic intramammary infection and induced worse clinical outcomes. Intramammary antibiotic treatment of most mild and moderate cases of CM caused by E. coli is not necessary, but more research is needed to identify which quarters affected by Kleb. pneumoniae may benefit from antimicrobial therapy.
Fuenzalida MJ
，Ruegg PL
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