Therapeutic Strategies for Contagious and Non-contagious Mastitis

Abstract

In recent years veterinarians and dairymen have reevaluated the advisability of treating clinical mastitis with antibiotics in herds where most of the clinical mastitis is caused by environmental pathogens. Most of the commercial antibiotic products available in the United States were tested against subclinical infections with contagious pathogens. A review of the current literature shows that antibiotics generally make no difference in the outcome of gram-negative intramammary infections. In gram-positive infections, the benefit of antibiotics depends on the pathogen. Streptococcus agalactiae infections respond well to therapy with any of the intramammary preparations available in the US. Staphylococcus aureus infections are generally refractory to antibiotic therapy according to the labels of the commercial tubes. The success of treatment may be increased by using antibiotics in conjunction with parenteral antibiotics or for longer durations than on the label. Coagulase-negative staphylococci generally cause mild mastitis in which antibiotic therapy makes little difference. The environmental streptococci are emerging as important and tough pathogens. Antibiotic therapy increases the success rate of treatment and may help prevent relapses and chronicity, but. more research is needed in this area.

No one protocol for treatment of clinical mastitis can be applied to all farms. Recommendations should be based on analysis of bulk tank and clinical samples and of the milking and management practices on the farm. Since clinical judgment and extralabel use of drugs is generally involved, the knowledge and advice of the veterinarian are essential in developing and evaluating treatment protocols. A suggested protocol for use in large herds that have little or no contagious mastitis will be presented.