Back in the 1940s, the discovery of synthetic insecticides was a major breakthrough in the control of vector-borne diseases. Large-scale indoor spraying programmes during the 1950s and 1960s succeeded in bringing many of the major vector-borne diseases under control. By the late 1960s, many of these diseases – with the exception of malaria in Africa – were no longer considered to be of primary public health importance. This triggered a major setback. Control programmes lapsed, resources dwindled and specializes in vector control disappeared from public health units. Within the past two decades, many important vector-borne diseases have re-emerged or spread to new parts of the world. Traditionally regarded as a problem for countries in tropical settings, vector-borne diseases pose an increasingly wider threat to global public health, both in terms of the number of people affected and their geographical spread. Their potential to spread globally, changes in climate, ecology, land-use patterns, and the rapid and increased movement of people and goods is threatening more than half the world’s population. Environmental changes are causing an increase in the number and spread of many vectors worldwide.
Dengue, in particular, is emerging as a serious public health concern. In 2012, it ranked as the most important mosquito-borne viral disease with epidemic potential in the world. There has been a 30-fold increase in cases during the past 50 years, and its human and economic costs are staggering. The primary vector for dengue, the Aedes aegypti mosquito, is now found in more than 20 European countries. This same mosquito species recently carried chikungunya to the Caribbean islands; the first cases of this debilitating disease seen in the Region of the Americas.
Alongside this alarming spread of vectors is the serious concern of increasing insecticide resistance. Today most species of vectors are showing resistance to many classes of insecticides. If existing insecticides lose their effectiveness this could erase all the gains made against malaria and other vector-borne diseases especially in parts of Africa. And at the same time, the world is facing an extreme shortage of entomologists and vector control experts. Very few African countries have entomology programmes at an undergraduate university level and some countries have only a handful of expert entomologists.