“House Plasmodial Prevalence Index” Another Relevant Indicator of Evaluating a Malaria Vector Control Operations, Example of Capango Village (Benguela Province, Angola)

Abstract

The WHO fascicule “Information systems for the evaluation of malaria control programmes” identified as outcome target “the proportion of households targeted for use of nets using at least one impregnated bednet” [1]. The parasitological evaluation of the efficacy of vector control programme is mainly based on the plasmodial prevalence rate evaluated by cross sectional or longitudinal surveys on representative sample of the human population targeted. For the new “House plasmodial” index we decided to combine the 2 indicators: the classical human plasmodial prevalence and house considering as positive any house with “at least one symptomless inhabitant having at least one positive thick film during the survey”. We used this new indicator when analyzing data gained during 24 regularly done parasitological surveys during 5 years in Capango village where a vector control (VC) programme was implemented using both Long Lasting Nets PermaNet© 2.0 and deltamethrin treated wall lining called ZeroFly© inside every house. Surveys were done during 2 years before VC and 3 years after. It appeared that the House Plasmodial positive index showed the same trends and level as the classical human plasmodial prevalence and clearly indicated the impact of vector control in reducing the overall plasmodial prevalence in the targeted village. On the other hand it appeared repeating surveys identified “frequently positive houses” (=found positive in some 50% of surveys) and therefore to be prioritized for control and those “scarcely positive” (20% of surveys). The House Plasmodial Prevalence index appeared relevant and reliable, interesting to be used in vector control programme while easy to get and should be considered in other epidemiological situation.