This has been the main strategy employed by public health in battling the spread of dengue. Putting Abate in breeding spots to destroy mosquito larvae and spraying insecticides to kill adult mosquitoes has been a constant feature in many areas designated as hot spots for dengue. There are concerns that mosquitoes are developing resistance to conventional insecticides.
Identifying these hotspots is reliant on reports from dengue cases in hospitals. It is compulsory for hospitals and clinics to notify health authorities of any cases of dengue. With the presumption that Aedes mosquitoes fly within a 50-100 metre radius from the source (patient), containment of aedes mosquitoes is concentrated as such. However, research has shown that a female mosquito can cover up to 840 metres from the source to lay its eggs. (Reiter et al, SHORT REPORT: DISPERSAL OF AEDES AEGYPTI IN AN URBAN AREA AFTER BLOOD FEEDING AS DEMONSTRATED BY RUBIDIUM-MARKED EGGS ,Am. J. Twp. Med. Hyg.. 52(2). 1995, pp. 177-179)
So perhaps we have underestimated the flying range of infected mosquitoes in considering our public health strategies. We also need to liase with entomologists in identifying if our mosquitoes are indeed developing resistance to our usual insecticides.
Campaigns to keep our drains and surrounding areas free of mosquito breeding spots need to be continuous. Aggressive monitoring of high risk areas, for example, construction sites, factories and squatter areas, need to be employed. Heavier penalties also need to be meted out, if we are to send a deterrent to harbouring aedes mosquitoes. Our education system needs to incorporate and inculcate knowledge of tropical diseases prevalent in Malaysia, in particular dengue.
Bio-engineering mosquitoes must be continuously considered. To our knowledge, there has been experiments in several areas where genetically engineered mosquitoes were released to mate with female mosquitoes in the wild. The offsprings are supposedly to live a shorter life and therefore be of no threat to humans.
There was also an experiment involving a bacteria infected mosquito (Wolbachia). Female mosquitoes infected with this genus of bacteria is unable to produce offpring. This will then control the mosquito population in dengue infested areas.
There are of course a lot of resistance from environmental groups who are concerned that bio-engineered mosquitoes can alter the delicate balance of the ecosystem. This is unsubstantiated and may be a viable option in the current epidemic scenario.
Finally there is the dengue vaccine. There is currently no approved vaccine. Prior trials have not conferred immunity to all serotypes of dengue virus. Trials are continuing in this area.
Newer immunological pathways are being explored in the case of dengue infection. As a greater understanding emerge, there is a likelihood that this infection can be stopped before it does damage to the body. However, it is likely not in the next few years and many more will likely die as a result. Even if a vaccine is available, it will likely be costly and its long term effects may continue to fuel debate on its safety.
As for now, low tech approaches are likely best. It needs to be continuous with the same intensity for long periods, if we are to ensure any impact on the control of dengue infections.