INTRAFAMILIAL TRANSMISSION OF LEPROSY IN VELLORE TOWN, INDIA

A hospital-based study was done from 1968 to 1991 to determine the ris k and extent of intrafamilial transmission of leprosy in relation to t he characteristics of the index cases and contacts in urban areas in I ndia. Families were examined by doctors annually. Skin smears were don e for contacts of multibacillary (MB) leprosy patients. Person years o f follow up were computed for each contact and used as the denominator for computation of incidence rates. Specific rates were computed by a ge, sex, type of leprosy, smear in index cases, age at registration, a nd sex of contacts. Of the 120 index cases (81 males, 39 females) 44% were MB; 410 contacts (186 males, 224 females) and 14 co-prevalent cas es were registered. The cumulative years of follow up was 2725 years. Fourteen contacts developed the disease (9 TT, 3 indeterminate, and 2 BT); 85.7% were in the 0-14 age group; 12 of 14 patients were detected to have leprosy during the first 5 years. The incidence rate OR) was 5.1/1000 (males 5.15, females 5.12). The IR was 7.3/1000 and 2.3/1000 among contacts of MB and paucibacillary leprosy patients (p < 0.05). T he IR in multiple-case families was 1.8. The importance of active surv eillance by a hospital-based survey is emphasized. It should be design ed to focus on children younger than 15 years and should be limited to 5 years of follow up.