Equine Rhodococcus equi Pneumonia in Foals – NAVLE Study Guide

Overview and Clinical Importance

Rhodococcus equi is a gram-positive, facultative intracellular bacterium that causes chronic suppurative bronchopneumonia with abscessation in foals aged 1-5 months. It is the most common and serious cause of pneumonia in young foals and represents a significant economic burden on endemic breeding farms due to prolonged treatment, surveillance costs, and mortality rates of 20-40%.

The disease is insidious in onset, meaning clinical signs often do not appear until pulmonary infection has reached a critical mass. This characteristic makes early detection challenging but crucial for successful treatment outcomes. R. equi is a soil saprophyte found worldwide, with airborne transmission via dust inhalation being the primary route of infection in foals.

Etiology and Epidemiology

Organism Characteristics

Rhodococcus equi (formerly Corynebacterium equi) belongs to the Nocardiaceae family, which also includes Mycobacterium and Nocardia species. Key microbiologic features include: