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Line 1: − <big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big>+ − <big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big>+ + − ===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 [[Respiratory Bacterial Infections - Pathology#Rhodococcus equi|bronchoneumonia]] + − ===Characteristics===+ − *Grows on non-enriched media+ − *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 − + − *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'' − *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 + − ===Clinical infections===+ − *[[Respiratory Bacterial Infections - Pathology#Rhodococcus equi|Bronchoneumonia]] and lung abscessation in foals less than 4 months+ − *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 [[Peritoneal Cavity Inflammatory - Pathology#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 + + − ===Diagnosis===+ − *History of disease on the farm, age of foals affected and clinical signs+ − *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 + + − + + + − *Oral rifampin and erythromycin for 4-10 weeks+ − *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+ + + + + + + + + + + + + + + + + + + + + + + + + + +
→Introduction
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== Introduction ==
[[Image:Pyogranulomatous lungs due to Rhodococcus Equi.jpg|thumb|right|200px|<small><center>Pyogranulomatous lesions due to ''Rhodococcus equi'' (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
''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 [[Bronchopneumonia|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 clinical 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 rattles 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.
Foals over 6 months are refractory to pulmonary infection, but superficial abscesses may occur.
===Pathogenesis and pathogenicity===
== 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. Sonography of the lung shows small abscesses close to the pleura in a very early stage, even before clinical signs can be seen. White blood cell cound (WBC) is rising in an early stage, too.
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.
PCR from the tracheobronchial mucus is a safe method to confirm diagnosis.
== Treatment and Control ==
Starting the treatment in an early stage is important for the success!
Affected farms should be screened regularly. Clinical examination, WBC and sonography of the lung are effective tools to catch the disease early.
Oral rifampin and erythromycin for 4-10 weeks is the treatment of choice for this disease. In Germany the treatment of choice is Tulathromycin (Draxxin by Pfizer), which is given i.m. every week for 4-8 weeks.
Rehydration therapy if diarrhoea is involved may be needed. Bronchodilators and expectorants should be used supportively.
Sonography of the lung and clinical examination are the best control for treatment´s success.
Control measures include preventing build-up of bacteria in environment by removing manure from pastures often and rotating foals and mares onto clean pastures regularly. Dusty conditions in paddocks should be avoided. In sickly looking foals, hyperimmune serum from the dam may be given to the foal in the first month of life.
===Treatment/control===
{{Learning
|flashcards = [[Equine Internal Medicine Q&A 17]]
|full text = [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.]
[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.]
}}
== References ==
There are many dissertations from Hannover University (summary in English):
:[http://elib.tiho-hannover.de/dissertations/kerthr_ws05.html Evaluation of the efficacy of Tulathromycin in the treatment of lung abscesses in foals]
:[http://elib.tiho-hannover.de/dissertations/heyersp_ss05.html Comparison of the detection of Rhodococcus equi by microbiological culture and the polymerase chain reaction in tracheobronchial fluid from foals]
Althaus, O.P., (2004) '''Sonographie der Lunge: Eine Hilfe zur Früherkennung der Rhodococcus equi-Pneumonie beim Fohlen,''''' Diss. Tierärztliche Hochschule Hannover ''
Brown, C.M, Bertone, J.J. (2002)''' The 5-Minute Veterinary Consult- Equine''', Lippincott, Williams & Wilkins ''Blackwell''
Kerth, R., (2005) '''Untersuchung der Wirksamkeit von Tulathromycin bei der Behandlung von Lungenabszessen bei Fohlen,''''' Diss. Tierärztliche Hochschule Hannover''
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''
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[[Category:Bacteria_miscellaneous]] [[Category:Gram_positive_bacteria]] [[Category:Cocci]] [[Category:Rods]] [[Category:Horse_Bacteria]] [[Category:Expert_Review - Horse]] [[Category:Respiratory_Bacterial_Infections]] [[Category:Respiratory_Diseases_-_Horse]]