[Overview of the geography of intestinal schistosomiasis in Brazil].
The distribution of schistosomiasis in Brazil is highly contrasted, with most cases concentrated in a large area in the North East, where the disease is endemic and considered a major threat to public health, and small isolated foci of disease scattered throughout the country seen as being of little epidemiological importance. The common interpretation of the history of this endemic disease (that it began in the endemic zone and has spread to the isolated foci) has added to the stigmatization of the North East. However, this interpretation is challenged by many examples of the recent establishment of the disease in the North-East and its more long-standing nature in the isolated foci. Besides, overstressing the role of recent migration simply obscures both social issues and the biogeography of vectors. Areas are not homogeneous in terms of schistosomiasis and we must therefore consider these factors if we are to understand the spread of the disease and its current distribution. Thus, in Amazonia, low human population pressure and the rarity of snails (mainly due to the acidity of the water) together account for the low level of transmission despite the high proportion of infected individuals among immigrants to this area. The converse is true for the city of Belém. Very similar reasons can be given for the limited impact of schistosomiasis in the central plateau and its high frequency around the federal capital, Brasilia. In contrast, the rate of infection is not very high around São Paolo due to the specific characteristics of urbanization of this city and its highly efficient control program. However, the enormous size of this city results in the number of cases reported being similar to that for Belém or Brasilia. These three cities are linked by a highway, which serves as a major axis for migration, particularly for those heading north from southern Brazil or São Paolo. This migration axis has increased in importance because there are now far fewer opportunities to settle in the West (Amazonia and the central plateau). The older "endemic territory" of the North East is experiencing a process of concentration of its cases of schistosomiasis in its larger cities, Recife and Salvador in particular. Thus, this endemic disease is becoming more urban and a network of five major cities, widely dispersed geographically, with high levels of infection, is emerging.
Brillet
P
P
Département de santé publique de la Faculté de pharmacie, université d'Angers, 16, boulevard Daviers, 49100 Angers. phbrillet@hotmail.com
D001938:Brazil / Q000453:epidemiology; D006801:Humans; D007411:Intestinal Diseases, Parasitic / Q000453:epidemiology*; D012424:Rural Population; D012552:Schistosomiasis / Q000453:epidemiology*; D014505:Urban Population