A seroepidemiological study of leprosy in high- and low-endemic Indonesian villages

A seroepidemiological study was performed in three different leprosy-endemic areas in Indonesia, including two isolated villages with high endemicity in South Sulawesi (Kaluarang and Hulo) and an area with low endemicity in Java (Jepara). A total of 2430 serum samples were collected from 2672 individuals in these locations. The prevalence of leprosy in these three areas, as determined during this study, was 29/1000, 11/1000, and 7/1000 in Kaluarang, Hulo and Jepara, respectively. Two serological assays were employed in this study to detect antibodies against Mycobacterium leprae. One is an enzyme-linked immunosorbent assay (ELISA) based on the detection of antibodies to the species-specific epitope of phenolic glycolipid-I (PGL-I) of M. leprae. The second test, using inhibition of an ELISA reaction (ELISA-INH) detects antibodies to a species-specific epitope on the 36-kDa protein antigen of M. leprae. In comparison with clinical findings, the specificity of both serological tests was calculated to be 91%. The sensitivity of the ELISA was 97.6% for multibacillary (MB) cases and 56.8% for paucibacillary (PB) cases; for the ELISA-INH, it was 97.6% and 81.8% for MB and PB cases, respectively. Seropositivity rates were shown to be unrelated to sex, to Mitsuda skin-test reactivity, or to BCG vaccination status. The pattern of seropositivity was, however, clearly age-related, with high seropositivity in the age group 10-19 years and decreasing rates of positivity in the older age groups. Age-standardized seropositivity ratios were not correlated to the prevalence of leprosy when comparing the three areas. Therefore, it is not yet clear whether or not seropositivity reflects infection. If it does, other, as yet unidentified, factors may play a role in the natural history of the disease.