Treatment of Persistent Escherichia coli Mastitis on a Large Dairy

Abstract

In our previous clinical mastitis study (Ackerman, AABP 2003), 39% of Escherichia coli intamammary infections persisted more than 21 days. Since E. coli is isolated from less than 20% of clinical cases, persistent E. coli infections make up less than 10% of clinical mastitis cases. A protocol that includes treatment of all cows to address these persistent infections is neither practical nor cost-effective. Currently, many larger farms are not treating E. coli mastitis with antibiotic therapy. However, these infections can be serious and painful with a persistent high milk somatic cell count. In herds where milk from clinical mastitis cases is cultured and pathogens identified before treatment, use of antibiotics for E. coli infections may be both practical and costeffective. These E. coli cases meet the AMDUCA criteria for extra-label treatment of an infection that threatens the animal's well-being and does not respond to approved intramammary antibiotics. In this study, we evaluated two antibiotic treatments for their effect on persistent E. coli infections.