Detection of subclinical Mycobacterium leprae infection in children, contacts of leprosy cases, Fortaleza – Ceara´ , Brazil

Summary
Objectives: To investigate the subclinical infection of leprosy in contacts younger than 15 years old of new leprosy cases diagnosed at the Dona Libaˆnia Dermatology Center in Fortaleza, Ceara´.
Methods: This was a cross-sectional study involving 69 leprosy cases and 101 household contacts under 15 years old. Nasal secretion samples were collected in order to investigate the Bacilloscopic Index (BI) for M. leprae and to detect the DNA of the bacilli; we also investigated the seropositivity of the IgM antibody to the PGL- 1 antigen through the ML-Flow technique.
Results: Evaluating the positivity of all three techniques used in the study, we obtained a frequency of 33·7% for ML-Flow, 16·1% for PCR of DNA and 1·98% for BI in nasal secretion. The positivity for RLEP PCR and in the anti-PGL-1 indicates stimulation of the immune response and consequent subclinical infection. In our study, all positive BI cases were also RLEP PCR positive, which confirms the presence of the bacillus in the nasal mucosa of the studied contacts. The seropositivity to anti-PGL-1 was higher among the female sex, the ones between 11 and 15 years old and among the contacts of paucibacillary (PB) cases.
Conclusions: Such techniques when used together help the monitoring of contacts with greater risk of developing the disease, especially in childhood.