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*Causes [[Peritoneal cavity - inflammatory#Peritonitis|peritonitis]]
*Causes [[Peritoneal cavity - inflammatory#Peritonitis|peritonitis]]
*[[Bacterial infections#Rhodococcus equi|Pneumonia]] in foals
*[[Bacterial infections#Rhodococcus equi|Pneumonia]] in foals
===Overview===
*Gram-positive aerobic saprophyte found worldwide
*Found in soil and intestinal tract of animals
*Replicates at warm temperatures in soils contaminated by faeces of herbivores
*Opportunistic respiratory pathogen of foals under 6 months causing suppurative bronchopneumonia
===Characteristics===
*Grows on non-enriched media
*Salmon-pink mucoid colonies due to capsule and pigment production
*No haemolysis on blood agar
*Aerobic, non-motile
*CAMP test-positive
*Catalase positive, oxidase negative, weakly acid-fast
*Found as cocci and rods
*Intracellular pathogen
===Pathogenesis and pathogenicity===
*Organism present in faeces or healthy foals as well as adult horses
*Pastures can become heavily contaminated, leading to outbreaks
*Transmission via inhalation of dust contaminated with ''R. equi''
*Virulence associated with specific surface antigens encoded by a large plasmid
*Capsular polysaccharide and mycolic acids in cell wall prevent phagocytosis
===Clinical infections===
*Bronchopneumonia and lung abscessation in foals less than 4 months
*Acute disease in 1 month-old foals: acute fever, anorexia, bronchopneumonia
*Insidious disease in 2-4 month-old foals with coughing, dyspnoea, weight loss, exercise intolerance, loud, moist rales on lung auscultation
*Occasionally diarrhoea
*Granulomatous ulcerative enterocolitis and mesenteric lymphadenitis in some foals following ingestion of contaminated sputum
*Foals over 6 months refractory to pulmonary infection
*Superficial abscesses in horses over 6 months
*Occasional infections in pigs and cattle, causing cervical lymphadenopathy
*Subcutaneous abscesses and mediastinal granulomas in cats
*Pneumonia in HIV patients
===Diagnosis===
*History of disease on the farm, age of foals affected and clinical signs
*Auscultation and rediography of thorax confirms pulmonary disease
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