DENGUE is a neglected tropical disease listed by the World Health Organization. In other words, it is primarily a disease of disadvantaged communities who lack access to proper housing and basic amenities worldwide. The environment that favours mosquito breeding is inevitably hostile to humans. Environmental pollution, poor water management, and inadequate sewage disposal have become constant companions of Bangladesh鈥檚 rapid urbanisation. Waste and water management remain the most pressing issues for all city corporations and municipalities. Mosquitoes take full advantage of these conditions, spreading pathogens with ease and causing the loss of precious human lives.
Mosquito-borne diseases are no longer confined to the monsoon belt, nor restricted to Dhaka. Statistics show that the most severe dengue outbreak occurred in 2023, with September proving particularly devastating: around one-third of all dengue cases that year were reported in that month, along with about a quarter of the total deaths. October and November were also alarming. In 2024, the peak shifted, with October and November recording the highest number of cases, November being the worst. In 2025, July and August have already seen record numbers, with September starting on the same trajectory. The outlook suggests that this dangerous trend will continue for at least three more months. Had even a third of the preventive measures been effectively enforced, the situation would not have reached such a critical state.
Among the various control methods, pesticide application remains a key tool鈥攅specially during emergencies. Pesticides are typically applied at two stages of the mosquito life cycle: larvicides target larvae, while adulticides target adult mosquitoes. When applied scientifically鈥攊n the correct dosage, at the right time, and in the proper manner鈥攑esticides can significantly reduce mosquito density. In turn, this lowers both dengue incidence and mortality.
However, the quality of pesticides, their storage, manufacturing process, transportation, and the safe disposal of expired products must all comply with scientifically recognised standards and standard operating procedures, backed by effective legislation. Concerns have been raised as to whether the pesticides currently in use truly meet these standards. If this issue is not resolved, the long-term use of expired or substandard pesticides鈥攍acking the required levels of active ingredients and proper formulation鈥攚ill not only fail to control mosquito populations but will also severely disrupt ecological balance. Insufficient or inappropriate application often kills beneficial insects before the target species, thereby worsening the spread of harmful pests.
Reports also suggest discrepancies between the pesticide samples inspected at the time of procurement and those later applied in the field. Storage conditions after purchase can further reduce effectiveness. These uncertainties can only be eliminated through rigorous testing of the active ingredients in pesticides, with decisions guided by the results. Such testing must be conducted by accredited laboratories. Samples should be collected randomly, in the presence of expert teams, and tested under their direct supervision. Many believe that without verifying active ingredient levels, mosquito density cannot be reduced, nor can outbreaks and deaths from mosquito-borne diseases be curbed.
In a densely populated country like Bangladesh, public health often suffers neglect, much like food safety. At different times and in different circumstances, the most fundamental needs of the people are pushed aside. Yet every human life is invaluable. If even one preventable death occurs, it is an unacceptable loss. Responsibility for such losses rests collectively on society and the state鈥攖hose who die are not strangers, but our own people.
Testing the active ingredient is also critical for other reasons. Malathion, widely used in mosquito control, has been proven in several countries to harm the environment due to its toxicity. It is well known that when a pesticide is used continuously for five years, its effectiveness declines as insects develop resistance.
History also provides lessons. When Paul Hermann M眉ller discovered DDT in 1939, it was hailed as a miracle and earned him the Nobel Prize in Medicine in 1948. Yet within decades, it became a curse, with ample evidence documented in Rachel Carson鈥檚 landmark book Silent Spring. This underlines the need to prioritise environmentally friendly biological control methods, while rigorously testing the active ingredients of conventional chemical pesticides.
There is no alternative to a scientific, realistic assessment of pesticide use鈥攐ne that takes into account the health of both humans and the environment鈥攁nd to making policy decisions based on the evidence.
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Dr Md Golam Sharower is professor and head, department of entomology, National Institute of Preventive and Social Medicine.