Residual Transmission of Malaria: An Old Issue for New Approaches

Malaria is one of the most serious vector-borne diseases, affecting millions of people mainly in the tropics. Recently, a substantial decline in malaria incidence has been observed all over the world. Vector control is one of the key elements in achieving this world-wide malaria decline, with scaling up of Insecticide Treated Nets (ITNs) and the expansion of Indoor Residual Spraying (IRS) programmes contributing significantly. Besides the personal protec‐ tion, ITNs confer a community protection when wide coverage is assured, meaning that unprotected persons benefit from the large scale intervention [1]. IRS is only meaningful when applied at a large coverage. In the 2011 World Malaria Report [2], the percentage of households owning at least one ITN in sub-Saharan Africa is estimated to have risen from 3% in 2000 to 50% in 2011 while the percentage protected by indoor residual spraying (IRS) rose from less than 5% in 2005 to 11% in 2010. Household surveys indicate that 96% of persons with access to an ITN within the household actually use it [2]. Although these numbers might overestimate the real ITN use, they show that in recent years, several vector control measures were scaled up substantially. Despite these large increases in coverage, a widely held view is that with the currently available tools, namely vector control tools, intermittent preventive treatment, and early diagnosis and treatment, much greater gains could be achieved, including elimination from a number of countries and regions [3].