Trends in leprosy over fifty years in Gudiyatham Taluk, Vellore, Tamil Nadu.

This paper presents epidemiological trends over a fifty-year period observed in a defined population served by the Schieffelin Leprosy Research and Training Centre (SLR & TC), Karigiri, Vellore District in Tamil Nadu. It covers three distinct periods, namely, the pre-MDT era with dapsone monotherapy, the MDT era under a vertical leprosy control programme and the MDT era after leprosy control services were integrated into the general health services. Prevalence rates have declined steadily from 125 per 10,000 population at the time of introduction of MDT in 1982 to 5 per 10,000 at the time of integration in 1997 to less than 1 per 10,000 in 2005. The new case-detection rate was 5.4 per 10,000 when the field programme started in 1962, and held steady at 15-20 per 10,000 between 1970 and 1980. It then showed a gradual fall from 10.8 per 10,000 in 1985 to 3.9 at the time of integration, and continued to fall in the post-integration period and was 0.8 per 10,000 in 2005. The mean age at detection showed a gradual increase from 23.4 years in the dapsone era to 31.2 years in the post-integration period. The male: female ratio showed a preponderance of males almost throughout the reference period. While polar types of leprosy (TT & LL) were common in the dapsone era, more of borderline leprosy (BT & BL) cases was seen more recently. MB rates that were high initially, declined steadily during monotherapy and stabilized between 10% and 12% during the vertical MDT programme and is showing an increase in the post-integration-period. The proportion of cases with Grade 2 disability at registration showed a gradual decline during the monotherapy period, remained relatively unchanged at 8%-10% during the the MDT period, and showed a sharp rise in the immediate post-integration period before falling. Analysis of trends of leprosy in a well-defined geographical population over a fifty-year period gives useful information on how the disease has evolved over the years. It provides opportunities to explore the reasons for the changes observed, though one has to be cautious while interpreting such data due to changes in definition, the play of operational factors, and changes in policies and strategies.