Emerging pathogens: is Mycobacterium avium subspecies paratuberculosis zoonotic?

Recent advances in diagnostics address the historical scepticism3 about MAP causing Crohn's disease. The NOD2 genetic defect, which is associated with Crohn's disease, predisposes to intracellular bacterial infections.1' In patients with Crohn's disease, MAP DNA has been detected by PCR in up to 90% of cases, by in-situ hybridisation in 70% of cases,7 and by RT-PCR for MAP RNA in 100% of cases.8 MAP has also been cultured from human milk,9 faeces, intestinal tissues, and peripheral blood of patients with Crohn's disease.10 Additionally, MAP-specific serological tests are positive significantly more often in Crohn's disease patients than in controls.11