AN HISTORICAL REVIEW OF MALARIA, KALA-AZAR AND FILARIASIS IN BANGLADESH IN RELATION TO THE FLOOD ACTION PLAN

This paper reviews the evidence of a link between flood control and vector-borne disease in Bengal/Bangladesh. Malaria is historically associated with reduced flooding and embankment construction in the flood plains of Bengal. The land west and south of the Jamuna river was highly malarious in 1916 but is not so today. The lands east of the Jamuna now have a higher, though still small, risk. The reduction in health risk can be attributed to the intensification of land use and human population density. Although there are many mosquito species, the abundance of the former malaria vector appears to have declined as environmental change removed its breeding sites. Visceral leishmaniasis (kala-azar) is a serious disease which is fatal if left untreated. It occurs in irregular, periodic epidemics and is currently increasing in Bangladesh. In the past, malaria and kala-azar were confused and the prevalence of both may have been increased by embankment programmes. Both diseases are unstable and there is insufficient historical information to predict, with certainty, the consequences of environmental change. Reduced flooding accompanied by increased pollution will probably control the malaria vector. More information is needed about the response of the kala-azar vector to flooding Bancroftian filariasis is non-fatal but causes chronic morbidity. It has had a widespread but usually low prevalence in Bangladesh, with both rural and urban foci. There are few recent data. Increasing organic pollution and drainage obstruction are expected to favour the vector and increase transmission.