The nation-wide campaign against malaria in Venezuela

Abstract

Venezuela is considered divided into three regions: Costa-Cordillera, Llanos and Guayana, which are different in topographical, meteorological, social and economic characters. Malaria, as a result of the topographical and meteorological conditions, has played an important role in creating the difference between these regions. The main vectors of malaria in Venezuela are A. albimanus and A. darlingi, the first species being found mostly in the Costa-Cordillera, and the last one in all the three regions with different degrees of prevalence. A. albimanus is in part zoophilic; A. darlingi is mostly anthropophilic and a house resting mosquito. As a result they react differently to DDT house spraying. A. albimanus is intercepted and its larval population is apparently not reduced. A. darlingi is reduced and may be eradicated. Past studies show that the endemicity of malaria is low, with relatively small areas of hyperendemic malaria, and that its epidemicity is generally high. This is due to the fact that the two main vectors are less potent than the most important Ethiopian or Oriental ones. This epidemic tendency is particularly shown in the 5-year cycles of the disease, which appear to be connected with similar cycles in range fluctuation and population density of the vectors, especially A. darlingi, cycles which are common, though with different periodicities, to other neo-tropical species. The División de Malariología has organized an intensive DDT house-spraying programme since the end of 1945. Details of the whole organization are given. By the end of 1948 the percentage of houses of the malaria zone directly protected with DDT was 37·2, and probably at least 50 per cent, of the houses of this zone have been influenced. But as the regions with higher malaria prevalence have been already sprayed, the decline of malaria of the whole country is remarkable. The malaria death-rate fell from an average of 112·2 in the period 1941 to 1945 to 14·8 in 1948. The success so far obtained leads to the possibility of eradication of malaria from the country. This possibility is discussed, and attention is called to the fact that the action of DDT residual spraying should be measured only in terms of malaria reduction and not deduced a priori from studies of its effects on mosquitoes. It is emphasized that malaria eradication from large areas of the world will finally depend on the conviction that the malariologists themselves may have that it can be done.