Epidemiological Surveillance of Leprosy in Cameroon Using the ELISA Test with D-BSA and Tris-HCl as Buffer

Background: Early detection of leprosy is important for elimination, but most cases are diagnosed only when lesions occur and nerves and skin are damaged. The determination of the risk of contacts to develop leprosy is still unpredictable, and elimination is not possible as long as contacts can still develop the disease. Methods: A modified PGL-I ELISA using tris-HCl as buffer and D-BSA as antigen evaluated IgM leprosy antibodies for the detection of subclinical leprosy infection and monitor effective chemotherapy. This case-control study took place in a leprosy endemic area among lepers diagnosed clinically and bacteriologically, intra-familial and extra-familial contacts and controls consisting of patients attending a health facility for reasons other than leprosy. Results: The highest mean absorbance of positive sera was from leprosy patients (0.14 ± 0.06), contacts (0.12 ± 0.05) and controls (0.04±0.04). The proportion of sero-positive subjects for IgM anti-bodies to M. leprae was 43.5 % (95% CI: 37.6% 49.4%). Twenty-three (44.2%) discharged cases since 1985 were still sero-positive for leprosy IgM anti-bodies; 15 years after treatment. We found a risk factor of 6 among contacts and controls suggesting a high level of transmission. Boyo division had a higher seropositivity (51.5%) compared to Mezam division (30%). Positive cases were clustered among students (44.8%), farmers (42.5%), the self-employed (44.7%), those with paid employment (37.5%) and the unemployed (60.0%) (P=0.01). Conclusion: The PGL-I ELISA with D-BSA and tris-HCl as buffer is a useful epidemiological surveillance tool for the detection of sub-clinical leprosy infection and chemotherapy monitoring. The discharged patients who tested positive should be re-evaluated for relapses.