Leprosy remains a severe public health problem in the State of Pará, Brazil. Over 80,000 cases were detected during the last 20 years in Pará, and currently, the annual case detection rate (50/100,000 inhabitants) is three-fold higher than the Brazilian average. The main objective of this study was to develop a method combining anti-PGL-I serology and spatial epidemiology as a tool for reducing the leprosy disease burden in Pará. An initial cross-sectional survey was conducted in eight municipalities of Pará at the residences of people reported to be affected by leprosy during the last five to six years. A group of researchers with experience treating leprosy patients, including dermatologists, nurses, physical therapists and lab technicians, performed a dermatoneurologic clinical examination and collected blood samples to test for anti-PGL-I IgM in 1,945 household contacts (HHC) of the 531 reported cases. Additionally, 1,592 school children (SC), aged 6-20 years, from 37 randomly selected elementary and secondary public schools underwent the same clinical and serologic evaluation. The residential addresses of reported leprosy cases and the residences of the examined SC were georeferenced to determine the spatial distribution pattern of leprosy. Two years later, based on the previous serological data, we returned to two cities to re-examine the same subjects. To evaluate the significance of geographic information in detecting new cases, we also selected two new public schools located in high-risk areas for leprosy. High-risk areas were determined by the spatial analysis of the distribution of cases in one municipality. During the initial survey, 156 (8%) HHC and 63 (4%) SC were diagnosed as new leprosy cases; 806 (41.4%) HHC and 777 (48.8%) SC tested positive for anti-PGL-I. Spatial analysis of one selected municipality demonstrated heterogeneity in the distribution of leprosy cases, with spatial clusters of high and low detection rates in specific regions of the city (p<0.01). Additionally, 94.7% of the initially examined SC lived within less than 200 meters of a leprosy case registered during the six years prior to this study. During follow-up, the incidence of leprosy was significantly higher among seropositive individuals (22.3%) when compared to seronegative individuals (9.4%) (OR = 2.7; 95%CI = 1.29 – 5.87; p = 0.01); leprosy rates were also significantly higher among dwellers of residences with at least one seropositive subject (17.4%), compared with dwellers of residences with no seropositive subjects (7.4%) (OR = 2.6; 95%CI = 1.18 – 5.91; p = 0.02). Selecting schools located in areas of the city at high-risk of leprosy increased the efficiency of detecting new cases among SC (8.2%) when compared to randomly selected schools (4%) (p = 0.04). The data indicate a high rate of undiagnosed leprosy cases and of subclinical infection with M. leprae in the State of Pará. Anti-PGL-I serology and spatial epidemiology are effective tools to increase the early detection of new cases, and these methods should be used by the municipalities of Pará to help reach leprosy control targets.
|
