Difference between revisions of "Rhodococcus equi"

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== Introduction<br>  ==
  
===Overview===
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Rhodococcus equi is a gram-positive aerobic, intracellular, saprophyte found worldwide in the soil and in the intestinal tract of animals. It replicates at warm temperatures in soils contaminated by faeces of herbivores and is an opportunistic respiratory pathogen of foals under 6 months causing suppurative [[Respiratory Bacterial Infections - Pathology#Rhodococcus_equi|bronchoneumonia]].&nbsp;
  
*Gram-positive aerobic saprophyte found worldwide
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Pastures can become heavily contaminated leading to outbreaks of the disease. The organism can be present in the faeces of adult horses and also healthy foals, without causing clincal disease. Transmission can be via inhalation of dust contaminated with R. equi.<br>
*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 [[Respiratory Bacterial Infections - Pathology#Rhodococcus equi|bronchoneumonia]]
 
  
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<br>
  
===Characteristics===
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== Clinical Signs<br> ==
  
*Grows on non-enriched media
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[[Respiratory Bacterial Infections - Pathology#Rhodococcus_equi|Bronchoneumonia]] and lung abscessation in foals less than 4 months old. Acute disease in 1 month-old foals with signs such as acute fever, anorexia, bronchopneumonia. In older foals, 2- 4 months the disease is more insidious with signs such as coughing, dyspnoea, weight loss, exercise intolerance, loud, moist rattlles on lung auscultation. There is occasionally diarrhoea seen, due to granulomatous ulcerative enterocolitis, mesenteric lymphadenitis and [[Peritonitis|peritonitis]] in some foals following ingestion of contaminated sputum.<br>
*Salmon-pink mucoid colonies due to capsule and pigment production
 
*No haemolysis on blood agar
 
*No growth on MacConkey agar
 
*Aerobic, non-motile
 
*CAMP test-positive
 
*Catalase positive, oxidase negative, weakly acid-fast
 
*Found as cocci and rods
 
*Intracellular pathogen
 
  
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Foals over 6 months refractory to pulmonary infection, but superficial abscesses may occur in in horses over 6 months.<br>
  
===Pathogenesis and pathogenicity===
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<br>
  
*Organism present in faeces or healthy foals as well as adult horses
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== Diagnosis ==
*Pastures can become heavily contaminated, leading to outbreaks
 
*Transmission via inhalation of dust contaminated with ''R. equi''
 
*Organisms survive inside cells
 
*Virulence associated with specific surface antigens encoded by a large plasmid
 
*Capsular polysaccharide and mycolic acids in cell wall prevent phagocytosis
 
*Cell mediated response required to clear infection
 
  
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History of the disease on the farm, age of foals and clinical signs are used to make a presumptive diagnosis. Auscultation and radiography of thorax confirms pulmonary disease.
  
===Clinical infections===
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Samples of &nbsp; tracheal aspirates and pus from lesions need to be taken and cultured aerobically on blood and MacConkey agar for 24-48 hours. Characteristic salmon-pink mucoid colonies grow, due to capsule and pigment production.&nbsp;
  
*[[Respiratory Bacterial Infections - Pathology#Rhodococcus equi|Bronchoneumonia]] and lung abscessation in foals less than 4 months
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<br>
*Infection associated with under-developed cell-mediated immunity
 
*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, mesenteric lymphadenitis and [[Peritonitis|peritonitis]] 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
 
  
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== Treatment/control ==
  
===Diagnosis===
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Oral rifampin and erythromycin for 4-10 weeks is the treatment of choice for this disease. Rehydration therapy if diarrhoea is invloved may be needed. Bronchodilators and expectorantscan be used supportively if pneumonia is severe.<br>
  
*History of disease on the farm, age of foals affected and clinical signs
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Control measures include preventing build-up of bacteria in environment by removing manure from pastures regularly and rotating foals and mares onto clean pastures regularly.&nbsp;Dusty conditions in paddocks should be avoided and poo- picking should be performed regularlyto keep pastures clean. In sickly looking foals, hyperimmune serum from the dam may be given to the foal in the first month of life.&nbsp;
*Auscultation and rediography of thorax confirms pulmonary disease
 
*Specimens: tracheal aspirates and pus from lesions
 
*Culture aerobically on blood and MacConkey agar for 24-48 hours
 
*Colony characteristics and biochemical profile
 
*Quantitative faecal culture on selective media
 
  
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<br> [[Image:Pyogranulomatous lungs due to Rhodococcus Equi.jpg|thumb|right|100px|<small><center>Pyogranulomatous lesions due to Rhodococcus equi (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
  
===Treatment/control===
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== References ==
  
*Oral rifampin and erythromycin for 4-10 weeks
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Brown, C.M, Bertone, J.J. (2002) The 5-Minute Veterinary Consult- Equine', Lippincott, Williams &amp; Wilkins <br>Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) Equine Internal Medicine (Third Edition), Saunders.<br>Reed, S.M, Bayly, W.M, Sellon, D.C. (2004) Equine Internal Medicine (Second Edition) Saunders.<br>Robinson, N.E., Sprayberry, K.A. (2009) Current Therapy in Equine Medicine (Sixth Edition) Saunders Elsevier<br>Rose, R. J. and Hodgson, D. R. (2000) Manual of Equine Practice (Second Edition) Sauders. <br>
*Rehydration therapy; bronchodilators; expectorants
 
*Prevent build-up of bacteria in environment by removing manure from pastures regularly and rotating foals and mares onto clean pastures regularly
 
*Dusty conditions in paddocks should be avoided
 
*Hyperimmune serum from the dam may be given to the foal in the first month of life
 
  
 +
<br>
  
[[Image:Pyogranulomatous lungs due to Rhodococcus Equi.jpg|right|thumb|100px|<small><center>Pyogranulomatous lesions due to Rhodococcus equi (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
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== Literature Search ==
  
*Causative agent [[Rhodococcus equi|''Rhodococcus (Corynebacterium) equi'']]
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[[Image:CABI logo.jpg|left|90px]]  
*Important cause of sever, often fatal [[Granulomatous Pneumonia|granulomatous]] [[Pneumonia Overview#Infectious causes of pneumonia|pneumonia]] in foals
 
*Clinical signs include depression, cough, weight loss, respiratory distress, diarrhoea, arthritis, subcutaneous abscesses
 
*Bacterium survives phagocytosis and multiplies
 
*Bacterial toxins -> caseous necrosis in lungs -> attracts inflammatory cells -> pyogranulomatous pneumonia
 
*Grossly:
 
**Multiple firm nodules, usually no encapsulation
 
**Partial [[Atelectasis|atelectasis]]
 
*Histologically:
 
**Pyogranulomatous lesions
 
**Macrophages with ingested microorganisms in the alveoli
 
**Necrosis spreading through parenchyma
 
  
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<br> Use these links to find recent scientific publications via CAB Abstracts (log in required unless accessing from a subscribing organisation). <br><br><br> [http://www.cabi.org/cabdirect/FullTextPDF/2010/20103095411.pdf '''''Rhodococcus equi'' infection in horses: an overview.''' Rajesh Agrawal; Nishi Pande; Rajesh Katoch; Anish Yadav; Ajitpal Singh; Veterinary Practitioner, c/o Dr. A. K. Gahlot, Bikaner, India, Veterinary Practitioner, 2009, 10, 2, pp 187-188, 16 ref. - '''Full test article''']
  
*pathogen of the equine lung (and intestine)
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[http://www.cabi.org/cabdirect/FullTextPDF/2008/20083097718.pdf '''Review of the epidemiology and ecology of ''Rhodococcus equi.''''' Muscatello, G.; Lowe, J. M.; Flash, M. L.; McBride, K. L.; Browning, G. F.; Gilkerson, J. R.; Green, E. M.&nbsp;; American Association of Equine Practitioners (AAEP), Lexington, USA, Proceedings of the 53rd Annual Convention of the American Association of Equine Practitioners, Orlando, Florida, USA, 1-5 December, 2007, 2007, pp 214-217, 27 ref. - '''Full test article''']
*cutaneous abscesses, cellulitis in young horses
 
*CELLULITIS = deep suppurative infection often dissecting through tissue planes
 
  
==Literature Search==
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[[Category:Bacteria_miscellaneous]] [[Category:Gram_positive_bacteria]] [[Category:Cocci]] [[Category:Rods]] [[Category:Horse_Bacteria]] [[Category:To_Do_-_Bacteria]] [[Category:To_Do_-_Review]] [[Category:Respiratory_Bacterial_Infections]] [[Category:Respiratory_Diseases_-_Horse]]
[[File:CABI logo.jpg|left|90px]]
 
 
 
 
 
Use these links to find recent scientific publications via CAB Abstracts (log in required unless accessing from a subscribing organisation).
 
<br><br><br>
 
[http://www.cabi.org/cabdirect/FullTextPDF/2010/20103095411.pdf ''''' Rhodococcus equi'' infection in horses: an overview.''' Rajesh Agrawal; Nishi Pande; Rajesh Katoch; Anish Yadav; Ajitpal Singh; Veterinary Practitioner, c/o Dr. A. K. Gahlot, Bikaner, India, Veterinary Practitioner, 2009, 10, 2, pp 187-188, 16 ref. - '''Full test article''']
 
 
 
[http://www.cabi.org/cabdirect/FullTextPDF/2008/20083097718.pdf ''' Review of the epidemiology and ecology of ''Rhodococcus equi.''''' Muscatello, G.; Lowe, J. M.; Flash, M. L.; McBride, K. L.; Browning, G. F.; Gilkerson, J. R.; Green, E. M. ; American Association of Equine Practitioners (AAEP), Lexington, USA, Proceedings of the 53rd Annual Convention of the American Association of Equine Practitioners, Orlando, Florida, USA, 1-5 December, 2007, 2007, pp 214-217, 27 ref. - '''Full test article''']
 
 
 
[[Category:Bacteria miscellaneous]][[Category:Gram_positive_bacteria]][[Category:Cocci]][[Category:Rods]][[Category:Horse Bacteria]]
 
[[Category:To_Do_-_Bacteria]][[Category:To Do - Clinical]]
 
[[Category:Respiratory_Bacterial_Infections]]
 
[[Category:Respiratory Diseases - Horse]]
 

Revision as of 18:11, 12 March 2011

Introduction

Rhodococcus equi is a gram-positive aerobic, intracellular, saprophyte found worldwide in the soil and in the intestinal tract of animals. It replicates at warm temperatures in soils contaminated by faeces of herbivores and is an opportunistic respiratory pathogen of foals under 6 months causing suppurative bronchoneumonia

Pastures can become heavily contaminated leading to outbreaks of the disease. The organism can be present in the faeces of adult horses and also healthy foals, without causing clincal disease. Transmission can be via inhalation of dust contaminated with R. equi.


Clinical Signs

Bronchoneumonia and lung abscessation in foals less than 4 months old. Acute disease in 1 month-old foals with signs such as acute fever, anorexia, bronchopneumonia. In older foals, 2- 4 months the disease is more insidious with signs such as coughing, dyspnoea, weight loss, exercise intolerance, loud, moist rattlles on lung auscultation. There is occasionally diarrhoea seen, due to granulomatous ulcerative enterocolitis, mesenteric lymphadenitis and peritonitis in some foals following ingestion of contaminated sputum.

Foals over 6 months refractory to pulmonary infection, but superficial abscesses may occur in in horses over 6 months.


Diagnosis

History of the disease on the farm, age of foals and clinical signs are used to make a presumptive diagnosis. Auscultation and radiography of thorax confirms pulmonary disease.

Samples of   tracheal aspirates and pus from lesions need to be taken and cultured aerobically on blood and MacConkey agar for 24-48 hours. Characteristic salmon-pink mucoid colonies grow, due to capsule and pigment production. 


Treatment/control

Oral rifampin and erythromycin for 4-10 weeks is the treatment of choice for this disease. Rehydration therapy if diarrhoea is invloved may be needed. Bronchodilators and expectorantscan be used supportively if pneumonia is severe.

Control measures include preventing build-up of bacteria in environment by removing manure from pastures regularly and rotating foals and mares onto clean pastures regularly. Dusty conditions in paddocks should be avoided and poo- picking should be performed regularlyto keep pastures clean. In sickly looking foals, hyperimmune serum from the dam may be given to the foal in the first month of life. 


Pyogranulomatous lesions due to Rhodococcus equi (Image sourced from Bristol Biomed Image Archive with permission)

References

Brown, C.M, Bertone, J.J. (2002) The 5-Minute Veterinary Consult- Equine', Lippincott, Williams & Wilkins
Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) Equine Internal Medicine (Third Edition), Saunders.
Reed, S.M, Bayly, W.M, Sellon, D.C. (2004) Equine Internal Medicine (Second Edition) Saunders.
Robinson, N.E., Sprayberry, K.A. (2009) Current Therapy in Equine Medicine (Sixth Edition) Saunders Elsevier
Rose, R. J. and Hodgson, D. R. (2000) Manual of Equine Practice (Second Edition) Sauders.


Literature Search

CABI logo.jpg


Use these links to find recent scientific publications via CAB Abstracts (log in required unless accessing from a subscribing organisation).


Rhodococcus equi infection in horses: an overview. Rajesh Agrawal; Nishi Pande; Rajesh Katoch; Anish Yadav; Ajitpal Singh; Veterinary Practitioner, c/o Dr. A. K. Gahlot, Bikaner, India, Veterinary Practitioner, 2009, 10, 2, pp 187-188, 16 ref. - Full test article

Review of the epidemiology and ecology of Rhodococcus equi. Muscatello, G.; Lowe, J. M.; Flash, M. L.; McBride, K. L.; Browning, G. F.; Gilkerson, J. R.; Green, E. M. ; American Association of Equine Practitioners (AAEP), Lexington, USA, Proceedings of the 53rd Annual Convention of the American Association of Equine Practitioners, Orlando, Florida, USA, 1-5 December, 2007, 2007, pp 214-217, 27 ref. - Full test article