Promoting dengue vector surveillance and control

Although both entomological and epidemiological surveillance data have often been collected in countries, there are few instances in which health services integrate and fully utilize such information to control an outbreak and prevent its expansion.

Ideally, surveillance activities should include the rapid detection of human infection supported by valid clinical and laboratory diagnosis, vector surveillance and monitoring of environmental and social risk factors for dengue outbreaks to ensure that increased dengue transmission is detected early and that the response is rapid and appropriate.

Effective vector control measures are critical to achieving and sustaining reduction of morbidity attributable to dengue. Preventive and vector control interventions aim to reduce dengue transmission, thereby decreasing the incidence of the infection and preventing outbreaks of the disease.

Unlike other mosquitoes, Aedes aegypti is a daytime feeder; its peak biting periods are early in the morning and before dusk in the evening. Female Ae. aegypti usually bites multiple people during each feeding period. The mosquito mates, feeds, rests and lays eggs in and around urban human habitation. Ae. albopictus, a secondary dengue vector in Asia, has spread largely due to the international trade in used tyres (a breeding habitat) and other goods (for example, lucky bamboo). Ae. albopictus is highly adaptive and therefore can survive in cooler regions. Its spread is due to its tolerance to temperatures below freezing, hibernation and its ability to take shelter in microhabitats.

Any successful control effort must be centred on the ability to sustain the intervention with sound monitoring and evaluation. Control of dengue vectors has mainly been approached by source reduction, elimination of container habitats that are favourable oviposition sites and which permit the development of the aquatic stages; by tightly-fitting lids or covers on containers or by killing larval and pupal stages using insecticides. Carrying out pupal surveys in human habitations can identify which containers are most productive; treating only these productive containers can be as effective as dealing with all containers but is far more efficient. The ability of the vector to exploit unconventional sites to rest or lay eggs should not be underestimated: in the past few years, for example, breeding has been found in septic tanks and in rooftop gutters.