Social contact patterns and leprosy disease: a case-control study in Bangladesh.

Socioeconomic and culturally defined social contact patterns are expected to be an important determinant in the continuing transmission of Mycobacterium leprae in leprosy-endemic areas. In a case-control study in two districts in Bangladesh, we assessed the association between social contact patterns and the risk of acquiring clinical leprosy. Social contacts of 90 recently diagnosed patients were compared to those of 199 controls. Leprosy was associated with a more intensive social contact pattern in the home [odds ratio (OR) 1·09, 95% confidence interval (CI) 1·00-1·19, P = 0·043] and in the nearby neighbourhood (OR 1·07, 95% CI 1·03-1·11, P = 0·001). Although it is known that M. leprae spreads most easily within households of infected persons, in endemic areas social contacts within the neighbourhood, village or urban ward, also appear to be important for transmission. We advise that disease control measures in leprosy-endemic areas should not be limited to households, but include high-risk groups in the nearby neighbourhood of patients.

The spatial distribution of leprosy in four villages in Bangladesh: an observational study.

BACKGROUND: There is a higher case-detection rate for leprosy among spatially proximate contacts such as household members and neighbors. Spatial information regarding the clustering of leprosy can be used to improve intervention strategies. Identifying high-risk areas within villages around known cases can be helpful in finding new cases. METHODS: Using geographic information systems, we created digital maps of four villages in a highly endemic area in northwest Bangladesh. The villages were surveyed three times over four years. The spatial pattern of the compounds--a small group of houses--was analyzed, and we looked for spatial clusters of leprosy cases. RESULTS: The four villages had a total population of 4,123. There were 14 previously treated patients and we identified 19 new leprosy patients during the observation period. However, we found no spatial clusters with a probability significantly different from the null hypothesis of random occurrence. CONCLUSION: Spatial analysis at the microlevel of villages in highly endemic areas does not appear to be useful for identifying clusters of patients. The search for clustering should be extended to a higher aggregation level, such as the subdistrict or regional level. Additionally, in highly endemic areas, it appears to be more effective to target complete villages for contact tracing, rather than narrowly defined contact groups such as households.

The spatial distribution of leprosy cases during 15 years of a leprosy control program in Bangladesh: an observational study.

BACKGROUND: An uneven spatial distribution of leprosy can be caused by the influence of geography on the distribution of risk factors over the area, or by population characteristics that are heterogeneously distributed over the area. We studied the distribution of leprosy cases detected by a control program to identify spatial and spatio-temporal patterns of occurrence and to search for environmental risk factors for leprosy. METHODS: The houses of 11,060 leprosy cases registered in the control area during a 15-year period (1989-2003) were traced back, added to a geographic database (GIS), and plotted on digital maps. We looked for clusters of cases in space and time. Furthermore, relationships with the proximity to geographic features, such as town center, roads, rivers, and clinics, were studied. RESULTS: Several spatio-temporal clusters were observed for voluntarily reported cases. The cases within and outside clusters did not differ in age at detection, percentage with multibacillary leprosy, or sex ratio. There was no indication of the spread from one point to other parts of the district, indicating a spatially stable endemic situation during the study period. The overall risk of leprosy in the district was not associated with roads, rivers, and leprosy clinics. The risk was highest within 1 kilometer of town centers and decreased with distance from town centers. CONCLUSION: The association of a risk of leprosy with the proximity to towns indicates that rural towns may play an important role in the epidemiology of leprosy in this district. Further research on the role of towns, particularly in rural areas, is warranted.

Social distance and spatial distance are not the same, observations on the use of GIS in leprosy epidemiology.

Contacts of leprosy patients have a higher risk of developing clinical leprosy. Being a contact is defined socially, but with the introduction of geographical information systems (GIS) in infectious disease epidemiology, it is necessary to relate spatial distance to social distance. We measured the distances between patients and their socially defined contacts in northwest Bangladesh. Contact categories differ in mean distance to the index patients. Sixty-seven per cent of the high-risk contacts lived within 10 metres (m), while all low-risk contacts lived >10 m from the index patient. Classification based on intervals of spatial distance creates categories that contain contacts of different socially defined categories, illustrated by a category of people living between 10 m and 20 m consisting of 47% of high-risk contacts and 52% low-risk contacts. Classification of contacts based on the spatial distance, as performed with GIS techniques, produces other groups than with social definitions.

Estudio sobre la transmisión y un ensayo quimioprofiláctico en contactos de pacientes de lepra: resultados de Colep / No disponible

En este trabajo se describe el modelo metodológico y hallazgos del estudio COLEP. Los objetivos del estudio son determinar la efectividad de la quimioprofilaxis con una dosis única de rifampicina e la prevención de la lepra entre contactos de pacientes de lepra y hallar características de los grupos de contacto en mayor riesgo de desarrollar lepra clínica. Estas características deben resultar útiles para los programas de control de lepra. El COLEP es un ensayo agrupado y aleatorio, a dobe ciego y controlado por placebo para determinar factores de riesgo que caracterizan los subgrupos en mayor riesgo entre el grupo contacto total de un paciente y un estudio de cohortes utilizando un grupo de referencia de entre la población general para determinar la prevalencia e incidencia de la lepra en la zona de la población estudiada. El período de seguimiento fue de 4 años. Se desarrolló un sistema de codificación explicando la distancia física y genética del contacto al paciente. Este estudio de Bangladesh incluye 1037 pacientes recién diagnosticados y sin tratamiento previo y sus 21,867 contactos. La prevalencia de la lepra entre los contactos era de 7-3 por 1000. Un total de 21,708 contactos sin rasgos ni síntomas de lepra clínica se incluyeron en un ensayo quimioprofiláctico con una dosis única de rifampicina y aleatorio a nivel del grupo de contacto en cuanto tratamiento y placebo. Los resultados de este ensayo estarán disponibles en algunos años

In this article, we describe the design, methodology and recruitment findings of the COLEP study. The objectives of this study were to determine the effective-ness of chemoprophylaxis with a single dose of rifampicin in the prevention of leprosy among contacts of leprosy patients, and to find characteristics of contact groups most at risk to develop clinical leprosy. These characteristics should be usable by routine leprosy control programmes. COLEP consists of a cluster randomized, double-blind and placebo-controlled trial, a cohort study to determine risk factors characterizing the sub-groups most at risk within the total contact group of a patient, and a cohort study using a reference group from the general population to determine the prevalence and incidence of leprosy in the total population of the study area. The follow-up period will be 4 years. A coding system was developed describing the physical and genetic distance of the contact person to the patient. This study in Bangladesh includes 1.037 newly diagnosed and previously untreated leprosy patients and their 21.867 contacts. The prevalence of leprosy among contacts was 7.3 per 1.000. a total of 21.708 contacts without sings and symptoms of clinical leprosy are included in a trial of chemoprophylaxis with single dose rifampicin, and randomized at contact group level in treatment and placebo arms. The results of this large field trial will become available in the years to come

A study on transmission and a trial of chemoprophylaxis in contacts of leprosy patients: design, methodology and recruitment findings of COLEP.

In this article, we describe the design, methodology and recruitment findings of the COLEP study. The objectives of this study were to determine the effectiveness of chemoprophylaxis with a single dose of rifampicin in the prevention of leprosy among close contacts of leprosy patients, and to find characteristics of contact groups most at risk to develop clinical leprosy. These characteristics should be usable by routine leprosy control programmes. COLEP consists of a cluster randomized, double-blind and placebo-controlled trial, a cohort study to determine risk factors characterizing the sub-groups most at risk within the total contact group of a patient, and a cohort study using a reference group from the general population to determine the prevalence and incidence of leprosy in the total population of the study area. The follow-up period will be 4 years. A coding system was developed describing the physical and genetic distance of the contact person to the patient. This study in Bangladesh includes 1037 newly diagnosed and previously untreated leprosy patients and their 21,867 contacts. The prevalence of leprosy among contacts was 7.3 per 1000. A total of 21,708 contacts without signs and symptoms of clinical leprosy are included in a trial of chemoprophylaxis with single dose rifampicin, and randomized at contact group level in treatment and placebo arms. The results of this large field trial will become available in the years to come.

Tuberculosis and patient gender in Bangladesh: sex differences in diagnosis and treatment outcome.

SETTING: The public health sector of Bangladesh. OBJECTIVE: To assess gender differences in access to tuberculosis diagnosis and in tuberculosis treatment outcome in Bangladesh. METHODS: Information on the age and sex of a sample of patients in 1997 was collected from out-patient registers and tuberculosis laboratory and treatment registers in 59 thanas in three divisions in Bangladesh. RESULTS: The female/male ratio was 0.79 among 42,877 out-patients with respiratory complaints, 0.51 among 5,665 tuberculosis suspects undergoing sputum smear microscopy, 0.36 among 869 tuberculosis suspects with positive sputum smears, and 0.35 among 5,632 patients registered for tuberculosis treatment. Treatment was successful (cured or treatment completed) in 86% of female and 84% of male patients. CONCLUSION: Women in Bangladesh appear to have less access to public out-patient clinics than men, and if they present with respiratory symptoms they are less likely to undergo sputum smear examination. If examined, women are less likely than men to be smear-positive. No gender bias was observed in tuberculosis treatment outcome. It is recommended to focus further research on exploration of sex differences in the incidence of respiratory conditions, identification of constraints among women in accessing out-patient clinics and verification of the quality of sputum submitted by women for examination.