Rhodococcus equi Disease Guidelines

Rhodococcus equi (R. equi) remains the most common cause of subacute or chronic granulomatous bronchopneumonia in foals less than 5 months of age. Extrapulmonary disease is not uncommon (see below). This gram-positive intracellular bacterial pathogen is normally present in the environment and in the manure of herbivores, making control and prevention extremely difficult.

The most common clinical manifestation of R. equi infections in foals is bronchopneumonia of variable severity, generally first noted at 2 to 6 months of age. Early clinical signs may include fever, lethargy, and/or anorexia, which are non-specific and can be easily missed. As the pulmonary infection progresses, clinical signs of pneumonia develop including tachypnea and increased respiratory effort (nostril flaring and abdominal effort). Nasal discharge (purulent) and cough are unreliable signs. Clinical signs may be more evident in hot and humid environments.