Rhodococcus Enterocolitis
Basic Information 
Clinical Presentation
Physical Exam Findings
• Pyrexia is common but not always observed
• Variable dehydration and evidence of endotoxemia and hypovolemia
• Hypermotile, “fluidy” GI borborygmi and diarrhea
• Evidence of involvement of the other organ systems may be noted
Tachypnea, increased respiratory effort, nasal discharge, cough, and adventitious lung sounds on thoracic auscultation with concurrent pneumonia
Etiology and Pathophysiology
• R. equi is an intracellular gram-positive coccobacillus. The organism is ubiquitous in the soil. It primarily causes suppurative bronchopneumonia and pulmonary abscessation in foals but can also affect other body systems.
• Exposure to R. equi may occur through inhalation or ingestion of organisms from the soil or from the feces of adult horses or foals.
• Host-environment-pathogen interactions are key for the development of clinical R. equi infection in some foals and avoidance of clinical disease in others because most foals are exposed to R. equi, but not all develop clinical disease.
• Intestinal lesions associated with R. equi are characterized by multifocal ulcerative enterocolitis with lesions predominantly located in the Peyer’s patches.
• Concurrent granulomatous inflammation in mesenteric and colonic lymph nodes is common, and large mesenteric abscesses may develop.
Diagnosis 
Differential Diagnosis
• Proliferative enteropathy (Lawsonia intracellularis)
• Gastroduodenal ulcer disease
• ± Cyathostominosis in older foals
• See “Salmonellosis,” “Diarrhea of the Neonatal Foal,” “Diarrhea, Clostridial,” “Proliferative Enteropathy,” “Gastric Ulceration in Foals,” and “Cyathostominosis” in this section
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