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Clin. Vaccine Immunol. doi:10.1128/CVI.00372-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Risk and protective factors for leprosy development in an epidemiological surveillance of household contacts

Leprosy National Reference Center, Clinics' Hospital, School of Medicine, Federal University of Uberlândia (UFU), Uberlândia, MG.; Institute of Genetics and Biochemistry, Federal University of Uberlândia (UFU), Uberlândia, MG

^* To whom correspondence should be addressed. Email: isagoulart{at}centershop.com.br.

	Abstract

Household contacts of leprosy patients are the highest risk group for the development of the disease, and although many risk or prevention factors have been identified, they have not been employed in leprosy monitoring programs. This investigation aimed to establish the relative risks or the preventive effects for the presence of BCG vaccination, the Mitsuda test, and the ML-Flow assay. Household contacts (1396) were followed for a five-year period. Twenty-eight contacts (2%) developed leprosy and had their clinical and operational classifications established. All immunological tests were performed, and intradermal BCG vaccination was given after the BCG scar count. Of the affected contacts, 75% developed the disease in the first year, and 71.4% were classified as paucibacillary forms. Contacts of lepromatous leprosy patients presented a 3.8-fold higher risk of developing leprosy. BCG vaccination and the Mitsuda test showed a protective effect against leprosy of 0.27 ( one scar) and 0.16 (> 7mm), respectively, and the positive ML-Flow test indicated a relative risk approximately 6-fold higher for occurrence of the disease. All unfavorable combinations of two and three assays generated significant risk values that ranged from 5.76 to 24.47, with the highest risk given by the combination of no BCG scar, negative Mitsuda test and positive ML-Flow. We suggest that the BCG vaccination may be given to stimulate Mitsuda test positivity, reducing the patient's risk of developing MB forms. The high significance of these tests may have a great impact on programs to monitor contacts and should be used to improve early detection and treatment.