Neil M. Ampel, MD reviewing Araujo S et al. Clin Infect Dis 2016 Dec 1.

Mycobacterium leprae DNA was found in the nasal passages of about half of 104 household contacts of leprosy patients; 7 contacts went on to develop active disease.

People with untreated leprosy have been considered the main source of subsequent infections. However, the route of transmission has been unclear. To ascertain whether airborne transmission is possible, investigators in Brazil collected samples from the nasal vestibules, nasal turbinate biopsies, and peripheral blood of 113 leprosy patients and 104 household contacts from 2003 to 2015. A real-time quantitative polymerase-chain-reaction (qPCR) assay was used to detect Mycobacterium leprae DNA. In addition, peripheral blood antibodies against M. leprae–native phenolic glycolipid I (PGL-I) were measured, and the lepromin skin test was used to assess delayed-type hypersensitivity.

Among people with leprosy, M. leprae DNA was detected in 75 (66%) of nasal swabs, 81 (72%) of nasal turbinate biopsies, and 22 (20%) of peripheral blood samples. Of the household contacts, 51 (49%) had M. leprae DNA detected in their nasal swabs, 56 (54%) in their nasal turbinates, and 7 (7%) in their blood. In addition, 19 (18%) had positive anti–PGL-I antibodies and 68 (65%) had a positive skin test. Seven household contacts developed clinical leprosy during a period of 5 to 7 years.

CITATION(S):

Araujo S et al. Molecular evidence for the aerial route of infection of Mycobacterium leprae and the role of asymptomatic carriers in the persistence of leprosy. Clin Infect Dis 2016 Dec 1; 63:1412. 

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