Academic journal article Bulletin of the World Health Organization

Spatial Patterns of Leprosy in an Urban Area of Central Brazil

Academic journal article Bulletin of the World Health Organization

Spatial Patterns of Leprosy in an Urban Area of Central Brazil

Article excerpt

Introduction

The occurrence and distribution of many infectious and parasitic diseases has changed because of the rapid growth of cities, internal migration, and socioeconomic changes in the least developed countries. Several studies have demonstrated the importance of rural-urban migration in disease patterns and the need to improve control strategies in urban settings (1-3).

In more than 90 countries, whose total populations amount to 2.4 x [10.sup.9], leprosy is endemic, with a prevalence of at least 1 per 10 000.(a) Although the introduction of multidrug therapy (MDT) in the 1980s made a major contribution to treating leprosy in most of the endemic countries, the disease is still an important cause of morbidity and physical deformities in Asia, Africa, and Latin America (4, 5).

Examination of the records of patients attending the routine services of specialized leprosy programmes has permitted time-trend analysis and comparisons between countries to be made (6-8). However, few studies have addressed the dynamics of leprosy transmission in urban environments in South America, particularly Brazil. To the best of our knowledge, the only study that did address this issue showed a rather variable distribution of leprosy cases among different socioeconomic census tracts in a highly urbanized area of south-east Brazil.(b) The need to improve understanding about the patterns of transmission of leprosy to facilitate the planning of health care services has encouraged the development of analytical tools based on studies of the geographical patterns of the disease (9-11).

This article reports the results of an ecological study designed to investigate the spatial variation of leprosy in an urban area and its relation to socioeconomic indicators, as a possible methodology to assist in the planning of health services.

Methods

Study area

The study was carried out in Goiania, central Brazil, a city of population 900 000 (population density, 520 inhabitants/[km.sup.2]), 99% of whom live in the urban area. A large proportion of the population migrated from rural areas during an intense migration influx in the mid-1960s. Over the last two decades the annual population growth rate has decreased from 6.5 to 2.3 per 100 due to an important decline in fertility rates and in internal migration waves (12).

Goiania is divided administratively into 64 districts, which are aggregations of census tracts and cover areas with broadly similar socioeconomic characteristics. These spatial units were conceived by the city council to define a framework for socioeconomic policy and research purposes.

The study area has the second highest leprosy endemicity in Brazil, with a prevalence and annual detection rate of 3.7/1000 and 56.7/100 000 inhabitants, respectively. The detection rate has increased by 8% per annum over the last 20 years (7, 13). The leprosy control programme in the city is based on passive case detection and treatment, and BCG vaccination of household contacts. Multidrug therapy (MDT), delivered as an outpatient regimen, is the first therapeutic choice for leprosy (13, 14). The local notification system is considered to be a reliable source of information, and is believed to include the majority of cases in this urban setting.

For the purposes of the study, a new case was defined as a person who showed clinical signs of leprosy and who had never been treated for the disease in the past. Case detection was carried out by trained doctors, and patients were classified on the basis of clinical signs and skin-smear results for allocation to MDT regimens. according to the Brazilian Leprosy Control Programme protocol.

The date of birth, address, date of first diagnosis, date of attendance, clinical type of leprosy, and the number of contacts were recorded for all newly diagnosed leprosy patients attending all seven outpatient clinics that provided treatment for leprosy patients in the city over the period November 1991 to October 1992. …

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