Clinical case report: First laboratory-confirmed diagnosis of Rhodococcus equi in a foal in Costa Rica

Abstract

Rhodococcus equi pneumonia is an important cause of morbidity and mortality in foals all over the world. Prevalence and/or virulence of bacteria is apparently low in Costa Rica since no outbreaks have been reported and suspicious cases show only mild to moderate clinical signs. However, there has never been a definitive diagnosis of the disease in Costa Rican horses. R. equi is a G (+) facultative intracellular bacteria causing pneumonia in young foals (up to 4-5 months of age). This paper refers to a 4-week old Friesian foal with a humerus fracture and omphalophlebitis that was referred to the Equine Hospital, National University, Costa Rica, for surgery. In the postoperatory period, the patient showed signs of moderate bilateral nasal discharge, cough, fever, lymphocytosis, and neutrophilia. The radiological evaluation of the thorax showed a bronchoalveolar pattern in the ventro cranial region of the lungs. The transtracheal aspirate cytology confirmed the presence of suppurative bronchopneumonia. The samples were aerobically cultured in Columbia agar + 5% blood at 37°C for 24h. The macroscopic, microscopic, and biochemical characteristics of the isolated bacteria, in addition to the partial sequencing of the “16SrRNA” gene, were compatible with R. equi. The foal was euthanized due to the humerus re-fracture before the R. equi diagnosis was confirmed. R. equi can potentially cause a severe monetary impact in the equine breeding industry; consequently, accurate diagnosis and treatments are important to avoid the emergence of resistant strains. Further studies are needed to determine the local prevalence of the pathogen and to evaluate its impact.