Fatal Rhodococcus equi infection in goats in southern Brazil.

Background: Rhodococcus equi is a Gram-positive, aerobic, cosmopolitan coccobacillus present in the soil and in feces of birds and a large variety of domestic mammals. It is the etiologic agent that commonly causes pneumonia in foals. This case report describes the clinical signs, lesions and the microbiological analysis of samples collected from three goats infected with Rhodococcus equi in a farm in southern Brazil. Cases: Three Boer goats died one week after presenting clinical signs that included: diarrhea, ruminal atony and anorexia (Goat 1); abortion, progressive weight loss, appetite loss, pale mucosas and tachycardia (Goat 2); and submandibular edema and anemia (Goat 3). Upon necropsy, it was shown that all goats presented multiple liver nodes between 0.5 and 3.0 cm in diameter. When sectioned these nodes presented yellowish contents that were not resistant. Additionally, Goat 2 presented nodes with caseous contents in mesenteric lymph nodes and lungs, which were similar to those observed in the liver. Upon necropsy, samples of organs were collected and fixed in 10% formaldehyde for histopathological analyses and kept under refrigeration for microbiological analyses. Histopathological analyses of liver, lung and lymph node of all goats revealed the presence of multifocal necrotic areas associated with the deposition of basophilic granular material (mineralization) surrounded by intense macrophage and neutrophil infiltration. Besides, moderate amounts of giant cells were also observed. Fite-Faraco staining showed coccobacillary structures in cytoplasm of macrophages and giant cells. The histopathological changes observed in this study are consistent with lymphadenitis, hepatitis and pyogranulomatous pneumonia. For the microbiological examination, samples were inoculated by direct imprint on Blood agar and MacConkey agar, and in Brain Heart Infusion enrichment broth at 37oC for between 24 h and 48 h. Subsequently, small, shiny, non-hemolytic mucoid colonies were observed, which were then submitted to Gram staining. Isolated colonies underwent biochemical differentiation. Rhodococcus equi was isolated by direct microscopy and the Gram method. Discussion: Rhodococcus equi sporadically affects goats, causing multiple hepatic and pulmonary caseous nodules. These lesions were observed in the samples examined in the present study. Differential diagnosis of rhodococcosis in goats includes caseous lymphadenitis and tuberculosis, although the etiologic agents of these diseases were not isolated in this study. In spite of the fact that Rhodococcus equi is isolated from the feces of herbivores, especially equines, no such animals were reared in the farm where the goats analyzed lived. Goats have been farmed in the property since 2006. It was not possible to determine the virulence of the agent. Nevertheless, new cases of rhodococcosis in goats indicate that infection by Rhodococcus equi may be more frequent in ruminants than it is expected, and play an important role in the differential diagnosis of caseous lymphadenitis. The detailed description of clinical signs and of the macroscopic and microscopic lesions associated with the isolation of the infectious agent confirm the diagnosis of rhodococcosis, and allow the veterinary doctor to list the possibilities in the differential diagnosis of the disease in goats with other granulomatous and pyogranulomatous diseases.