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Mycobacterium avium subspecies paratuberculosis is a cause of Crohn's disease
  1. J Hermon-Taylor
  1. Department of Surgery, St George's Hospital Medical School, London SW17 0RE, UK
  1. Dr J Hermon-Taylor.jhermon{at}

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Mycobacterium avium subspeciesparatuberculosis(MAP) belongs to theM avium complex (MAC). MAC occur widely in the environment and inhabit normal animal and human intestine. MAC do not usually cause disease unless the host is debilitated.MAP is a pathogen and causes chronic inflammation of the intestine in many animals, including primates.MAP is closely related genetically to other MAC but possesses additional DNA such as IS900, the hspX region, and the low %GC genetic element “GS”, which are associated with its pathogenic phenotype. Further genetic elements related to pathogenicity may be revealed by the whole genome sequencing ofMAP currently underway at the University of Minnesota. A recent review and extensive bibliography is available.1

MAP can colonise animals for years without causing disease. Chronic inflammation of the intestine (Johne's disease) may emerge after a long latent period, particularly when animals are stressed. Regional lymph nodes, liver, and lung are also involved. Histopathological features vary between animals and between different organs in the same animal.2 MAP disease in animals ranges from pluribacillary to paucimicrobial, like leprosy in humans.3Terminal ileum and adjacent colon are commonly affected but segmental lesions in the small gut as well as colonic and rectal involvement …

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