A Comparison of Betadine and Chlorhexidine For Drying-Off Mammary

Quarters

Chronically Infected With Staphylococcus aureus

John R. Middleton and Larry K. Fox

Washington State University

Pullman, Washington

Introduction A review of the current veterinary literature found only a single study evaluating

therapeutic dry-off of chronically infected mammary quarters (1). In that study the authors

used an infusion of chlorhexidine to cause cessation of lactation in chronically infected

mammary quarters. To date no studies have evaluated the ability of a therapeutically dried

mammary quarter to return to function in the subsequent lactation, nor has there been a

study to evaluate the efficacy of such a treatment in curing chronic intramammary

infections (IMIs). The purpose of the present study was to compare the ability of

chlorhexidine and betadine to cause cessation of lactation in the treated quarter, assess milk

production in the infused quarter in the subsequent lactation, and evaluate whether a

microbiological cure could be attained.

Materials and Methods Fourteen cows from the Washington State University dairy herd were identified as having

chronic, single quarter Staphylococcus aureus IMIs. Chronicity of S. aureus IMI was

determined by monthly quarter milk cultures performed prior to this study (2). A persistent

infection was defined as 2 out of 3 positive cultures. Cows were randomly assigned to one

of two treatment groups, betadine or chlorhexidine, such that every other cow received

chlorhexidine. Treatments were intramammarily instilled in the S. aureus infected quarters.

Milk production from each mammary quarter (kg of milk/quarter) was measured from all

cows for five consecutive days prior to treatment. Quarter milk weights were measured

again at the beginning of the subsequent lactation for five consecutive days to assess return

to function of the treated quarter. All cows were pre-treated with 600 mg of flunixin

meglumine (Banamine, Schering Plough, Union, NJ) intramuscularly 15 minutes prior to

infusion of either betadine or chlorhexidine. Cows in the betadine group were infused with

120 ml of 5% povidone-iodine solution (0.5% iodine) after quarter milk weight

measurements on the fifth day. Chlorhexidine treated cows were infused with a proprietary

chlorhexidine suspension (Nolvasan suspension, Fort Dodge Animal Health, Fort Dodge,

IA) after two milkings 24 hours apart. Treated quarters in both groups of cows were not

milked for the rest of the lactation. Milk from treated cows was withheld from the bulk tank

for 96 hours post-infusion. All non-infected quarters were infused with a dry cow

intramammary antibiotic at the end of lactation. To assess whether a microbiologic cure had

been obtained, quarter milk samples were collected monthly for the first three months of

the subsequent lactation and cultured for S. aureus. Cows having three consecutive negative

milk cultures for S. aureus were classified as cured.

Mean milk production in each quarter and mean milk weight difference (MMWD = mean

milk weight (kg) in the uninfected contralateral control quarter - mean milk weight (kg) in

the infected quarter) were calculated from measurements made prior to treatment and in the

subsequent lactation for each cow. Student's t-test was used to assess for significant

differences in milk production between groups.

Results Mean milk weights and milk weight differences are summarized in Table 1. None of the

cows in the betadine group produced milk in the treated quarter in the subsequent lactation,

whereas as 5 of 7 (71%) cows in the chlorhexidine group produced milk in the next

lactation. There was no significant difference in MMWD in the chlorhexidine group

(p>0.05) before treatment or in the next lactation, whereas the MMWD was greater after

treatment in the betadine group (p=0.0007). Microbiologic cures were obtained in 4 of 7

(57%) cows treated with chlorhexidine. No cures were obtained in the betadine group.

Table 1. Mean milk weights and milk weight differences in infected and control quarters

for cows

in each treatment group.

. Mean milk weight in kg by quarter

No. Cow Treatment Sample Period Infected Control Difference

7 Betadine Before Treatment 1.6 3.2 1.6

After Treatment 0.0 4.5 4.5

7 Chlorhexidine Before Treatment 2.3 2.5 0.3

After Treatment 1.9 3.3 1.4

Conclusions This study suggests that chlorhexidine has potential as a method of therapeutic dry-off for

mammary quarters chronically infected with S. aureus. While betadine appears to cause

permanent cessation of lactation in the treated mammary quarter, S. aureus can still be

cultured from that quarter in the subsequent lactation. Hence, betadine treated quarters may

remain a reservoir for infection of herdmates. Conversely, 71% of the chlorhexidine treated

quarters returned to lactation and greater than 50% of chlorhexidine treated quarters

became S. aureus negative. Therefore, production can be obtained, while the reservoir of

infection is diminished.

References 1. Boddie RL, SC Nickerson. 1993. Permanent Drying Off of Chronic Mastitic Quarters.

Louisiana Cattlemen. Nov: pp. 10-11.

2. Middleton JR, LK Fox, T Smith, et al. 1996. Intervention strategies to reduce the

incidence and prevalence of Staphylococcus aureus mastitis in a dairy herd. Proceedings

91st Annual Meeting of the ADSA, Corvallis, OR P137:163.

Presented at the National Mastitis Council 38th Annual Meeting, February 14-17, 1999.

Published in the 1999 National Mastitis Council Annual Meeting Proceedings, pg. 231.

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