More conservative use of antimicrobials does not adversely affect treatment outcomes in foal bronchopneumonia.

Overview

• This study investigated whether delaying antibiotic treatment in foals with bronchopneumonia reduces antibiotic use without negatively affecting recovery.
• The research found that treating foals later in the disease process reduced antibiotic usage but did not increase mortality, treatment failure, or recurrences.

Background and Motivation

• Antimicrobial resistance is a growing concern in both human and veterinary medicine.
• Bronchopneumonia, a lung infection, affects young foals and is often treated with antibiotics.
• Many foals with subclinical (mild or undetected) bronchopneumonia recover without treatment, prompting interest in more conservative antibiotic use.
• This study was designed to assess if delaying the start of antibiotic therapy until the disease is more advanced could reduce unnecessary antibiotic use.

Study Design

• A cohort of 1200 warmblood foals born over several years (2020, 2022, 2023, and 2024) on a single breeding farm was monitored.
• All foals were screened weekly using clinical exams, blood tests, and thoracic ultrasound to detect bronchopneumonia.
• Diagnosis was based on abscess size in the lungs, with a total abscess score ≥ 1.0 cm indicating bronchopneumonia.
• Two treatment threshold protocols were used:
  • 2020/2022: foals were treated when abscess scores reached or exceeded 15.0 cm.
  • 2023/2024: treatment was delayed until abscess scores reached or exceeded 20.0 cm.
• Treated foals received a combination of rifampin and tulathromycin antibiotics.
• Outcomes measured included:
  • Proportion of foals treated
  • Mortality rates
  • Treatment failure rates
  • Recurrence of disease
  • Duration of antibiotic therapy

Key Results

• The proportion of foals receiving antibiotic treatment dropped significantly from 29.0% in the 2020/2022 group to 17.5% in the 2023/2024 group.
• Mortality rates remained steady at approximately 1.0% in both time periods, indicating no increase in death despite delayed treatment.
• Treatment failure rates showed no statistical significance:
  • 2.8% failure in the earlier treatment group (2020/2022)
  • 8.6% failure in the later treatment group (2023/2024)
• Recurrence rates were low and similar between groups:
  • 2.3% in 2020/2022
  • 0.95% in 2023/2024
• The initial antibiotic treatment duration was slightly longer in the 2023/2024 group (25 days) compared to the earlier group (21 days).

Conclusions and Implications

• Delaying antibiotic treatment until more advanced lung lesions develop reduces the number of foals exposed to antibiotics.
• This approach does not increase death, treatment failure, or disease recurrence rates compared to earlier treatment.
• The findings support more conservative antibiotic use in foal bronchopneumonia, potentially helping combat antimicrobial resistance.
• There may be a slight need for longer treatment durations for those treated later, but this is offset by the overall reduction in treated cases.
• The study encourages careful monitoring and a threshold-based approach to initiating antibiotic therapy in veterinary respiratory infections.