The Health Department, in consultation with the World Health Organisation (WHO), is now readying to experiment with innovative vector control strategies in an attempt to win the war over dengue. This new direction is being contemplated because the sole reliance on conventional methods like source reduction, which targets the destruction of immature mosquito larvae, has had limited success in keeping vector densities at a level where disease transmission does not occur.
There is increasing consensus that there can be no single strategy which can effectively control a hardy species like Aedes Aegypti, the primary vector spreading dengue.
The decision to try out a combination of novel vector control interventions came during discussions with a visiting WHO team last month, which is part of a joint clinical epidemiology study on dengue being conducted in the State.
The idea is to invest in vector control measures that target adult mosquitoes, along with the usual methods of source reduction and dry day observance.
Insecticide resistance
Innovation in vector control is critical to dengue management because of concern over insecticide resistance, outdoor disease transmission, the need for effective tools to suit multi-disease settings and the rapid manner in which arbovirus diseases are spreading.
Aedes is a hardy species and even nations like Singapore, which has been implementing sustained vector control programmes for years still have to deal with explosive dengue outbreaks.
Globally, the new vector control tools being experimented to control Aedes species, with some amount of proven success, include the use of vector traps such as auto dissemination devices and adulticidal oviposition traps.
WHO has suggested that the State experiment with using lethal ovitrap or sticky gravid trap which attracts and kills female mosquitoes as they lay eggs. This is a simple and cost effective strategy which was initially used in Brazil in the 1970s and successfully replicated during the recent Zika epidemic. “The epidemiological efficacy of using vector trap as an integrated vector management strategy, especially in the case of day-time biters like Aedes, is yet to be fully demonstrated anywhere. As part of the ongoing study, we have now decided to test the efficiency of vector traps and insecticide-impregnanted curtains at the community level,” said P.S. Indu, Professor, Community Medicine, Thiruvananthapuram Medical College, and the lead investigator for the study. “We propose to indigenously develop the prototypes of various vector traps with the help of Vector Control Research Centre, Kottayam and conduct experimental trials at field-level,” she said.
