R. equi is a dangerous pathogen that causes pneumonia in foals that are generally between the ages of 3 weeks and 5 months. In cases that caretakers and veterinarians catch early on, the foal can make a full recovery with proper treatment. However in more serious cases, the mortality rate is quite high. | Photo: Anne M. Eberhardt/The Horse

Rhodococcus equi is a dangerous pathogen that causes pneumonia in foals that are generally between the ages of 3 weeks and 5 months. In cases that caretakers and veterinarians catch early on, the foal can make a full recovery with proper treatment. However, in more serious cases the mortality rate is quite high, noted Steeve Giguère, DVM, PhD, Dipl. ACVIM, at the 56th Annual Convention of the American Association of Equine Practitioners, held Dec. 4-8, 2010. He discussed the importance of understanding the pathogenesis of R. equi (how it’s acquired and how it causes disease), the associated clinical signs, and the diagnostic methods used to detect infection.

“The most common manifestation of R. equi  infections in foals is a chronic suppurative (pus-producing) bronchopneumonia with extensive abscessation,” Giguère said. “The slow spread of the lung infection combined with the remarkable ability of foals to compensate for the progressive loss of functional lung makes early clinical diagnosis difficult.”

Clinical Manifestations

Giguère closely analyzed the different clinical manifestations of R. equi pneumonia that the foals presented