BACKGROUND: Geographical differences in leprosy risk are not understood, but may provide clues about the natural history of the disease. We report an analysis of the geographical distribution of leprosy in Karonga District, a rural area of Northern Malawi, between 1979 and 1989. METHODS: Cohort study of the incidence of leprosy based on two total population surveys. Area of residence was determined using aerial photographs, which allowed identification of households, as well as location of roads, rivers and the lake shore. RESULTS: Incidence rates were between two and three times higher in the north compared to the south of the district, and lowest in the semi-urban district capital. The most obvious environmental difference between these regions is the north's higher rainfall and more fertile soil. There was no overall association between leprosy incidence and population density, although highest rates were observed in the least densely populated areas. Looking at the entire district, incidence rates increased with increasing distance from a main road, but declined with increasing distance from a river or from the shore of Lake Malawi. The negative association with proximity to rivers may reflect the larger number of rivers in the north of the district. Apparent differences in incidence rates between groups speaking different languages reflected confounding by area of residence. CONCLUSIONS: There is a marked variation, not explained by socioeconomic or cultural factors, in the incidence of leprosy within Karonga District. Our results are consistent with a theme in the literature associating the environment, particularly proximity to water, with leprosy.
BACKGROUND: Geographical differences in leprosy risk are not understood, but may provide clues about the natural history of the disease. We report an analysis of the geographical distribution of leprosy in Karonga District, a rural area of Northern Malawi, between 1979 and 1989. METHODS: Cohort study of the incidence of leprosy based on two total population surveys. Area of residence was determined using aerial photographs, which allowed identification of households, as well as location of roads, rivers and the lake shore. RESULTS: Incidence rates were between two and three times higher in the north compared to the south of the district, and lowest in the semi-urban district capital. The most obvious environmental difference between these regions is the north's higher rainfall and more fertile soil. There was no overall association between leprosy incidence and population density, although highest rates were observed in the least densely populated areas. Looking at the entire district, incidence rates increased with increasing distance from a main road, but declined with increasing distance from a river or from the shore of Lake Malawi. The negative association with proximity to rivers may reflect the larger number of rivers in the north of the district. Apparent differences in incidence rates between groups speaking different languages reflected confounding by area of residence. CONCLUSIONS: There is a marked variation, not explained by socioeconomic or cultural factors, in the incidence of leprosy within Karonga District. Our results are consistent with a theme in the literature associating the environment, particularly proximity to water, with leprosy.
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Keywords:
Africa; Africa South Of The Sahara; Bacterial And Fungal Diseases; Developing Countries; Diseases; Eastern Africa; Ecology; English Speaking Africa; Environment; Epidemiology; Geographic Factors; Health; Infections; Leprosy--determinants; Malawi; Population; Public Health; Research Report
Authors: José Wilton Queiroz; Gutemberg H Dias; Maurício Lisboa Nobre; Márcia C De Sousa Dias; Sérgio F Araújo; James D Barbosa; Pedro Bezerra da Trindade-Neto; Jenefer M Blackwell; Selma M B Jeronimo Journal: Am J Trop Med Hyg Date: 2010-02 Impact factor: 2.345
Authors: Gillian F Black; Rosemary E Weir; Steven D Chaguluka; David Warndorff; Amelia C Crampin; Lorren Mwaungulu; Lifted Sichali; Sian Floyd; Lyn Bliss; Elizabeth Jarman; Linda Donovan; Peter Andersen; Warwick Britton; Glyn Hewinson; Kris Huygen; Jens Paulsen; Mahavir Singh; Ross Prestidge; Paul E M Fine; Hazel M Dockrell Journal: Clin Diagn Lab Immunol Date: 2003-07
Authors: William H Wheat; Amy L Casali; Vincent Thomas; John S Spencer; Ramanuj Lahiri; Diana L Williams; Gerald E McDonnell; Mercedes Gonzalez-Juarrero; Patrick J Brennan; Mary Jackson Journal: PLoS Negl Trop Dis Date: 2014-12-18