The New South Wales mastitis control program. 2. Effect upon bacterial infections

Area of Science:

• Veterinary Microbiology
• Animal Health Management

Background:

• Bovine mastitis remains a significant economic challenge in dairy farming.
• Staphylococcus aureus and Streptococcus agalactiae are key pathogens contributing to mastitis.
• Antibiotic resistance patterns influence treatment efficacy and control strategies.

Purpose of the Study:

• To evaluate the effectiveness of a mastitis control program over a three-year period.
• To monitor changes in bacterial prevalence, particularly Staphylococcus aureus and Streptococcus agalactiae.
• To assess the impact of control measures on antibiotic resistance.

Main Methods:

• Bacteriological examination of quarter milk samples from 35 dairy herds.
• Longitudinal monitoring over a 3-year period.
• Analysis of bacterial prevalence and antibiotic resistance patterns.

Main Results:

• Mastitis control measures halved Staphylococcus aureus prevalence (from 26% to 13%) within 3 months, with significant herd variation.
• Streptococcus agalactiae infections were largely eliminated, though reinfection occurred in some herds.
• Limited impact was observed on Streptococcus uberis and Streptococcus dysgalactiae.
• Antibiotic resistance patterns, particularly penicillin resistance in Staphylococcus aureus and streptomycin resistance in Streptococcus agalactiae, persisted throughout the study.

Conclusions:

• Mastitis control programs can effectively reduce Staphylococcus aureus and Streptococcus agalactiae prevalence.
• Sustained monitoring and targeted interventions are crucial for managing mastitis and antibiotic resistance.
• The persistence of antibiotic resistance highlights the need for judicious antibiotic use in dairy herds.