The dengue virus has now spread from cities to remote rural areas. The population density of the Aedes mosquito, the vector of the dengue virus, is measured on the Breteau Index. The index is based on the presence of Aedes mosquito larvae in terms of the number found in wet containers in every 100 houses in a particular area.
The situation is considered vulnerable only if the value of this index is more than 20. But this Breteau value is 47.10 in the Barguna municipal area and 163.04 in the district headquarters. So, this shows how terrible is the density of mosquito population in an area. So, why will there not be a dengue epidemic there? There are two species of the Aedes mosquito that have carried the dengue virus in Bangladesh for a long time. These are Aedes aegypti and Aedes albopictus. A survey in 2024 showed that out of the two species, 99 per cent of Aedes species that were found in cities or towns were Aedes aegypti and 1 per cent of the mosquitoes were Aedes albopictus.
In villages, the picture is, however, completely opposite. A survey that the Institute of Epidemiology, Disease Control and Research conducted in collaboration with the National Institute of Preventive and Social Medicine and the University of Dhaka in 2024 found that 95 of the Aedes mosquitoes were Aedes albopictus and 5 per cent of them were Aedes aegypti in rural areas. This is because Aedes albopictus is called a forest mosquito. Its main breeding ground is natural sources, which could be the base of the leaves of banana trees, the bamboo grove, the leaf aisle of the taro and tree holes, etc.
Aedes aegypti is a domestic mosquito. It usually breeds in artificial water sources such as water collected in tyres, coconut husks, packets of chips, plastic containers, buckets, under-construction buildings, etc. The density of the mosquito depends on the type of buildings, location, the presence of water containers, cleanliness, etc. In suburbs, the density of Aedes albopictus depends on the proximity of houses. Why is the situation so terrible in villages compared with cities, especially in Barguna? Out of 9,867 dengue patients, 4,443 are reported to have been from the Barisal division and 2,669 of them are from Barguna. Out of 42 death so far caused by dengue, 12 were in Barisal and six of them were in Barguna.
What is the cause and remedy for this severity? The reason is the population density of mosquitoes. As the density of mosquitoes increases, the number of patients increases. The issue that needs to be considered seriously is, therefore, the presence of infected mosquitoes and public awareness. The density of Aedes albopictus has been there in villages. However, they were not infected with the dengue virus. Whenever a mosquito in a city infects someone in the village and it is not properly contained with specific contact tracing, because there was a lack of proper contact tracing, the infected mosquito becomes reckless.
It continues to carry out its attack without any hindrances. It continuously infects people through cross-transmission. And, the number of patients increases. The procession of death becomes longer. In the absence of proper public awareness, the number of death increases. People become disoriented. They become depressed because of the pain of losing members of their family or friends. The air of Barguna has, thus, gradually become heavier because of the cries of people. The people of Barguna have always lived, fighting with tbe nature. People there store water in containers because of the shortage of drinking water.
They do not understand that the Aedes mosquito larvae grow in the stored water and it is out of their consideration. They think that it is a normal water insect. But, the fact is that they are Aedes mosquito larvae, the main carrier of the dengue virus. People engaged in the struggle for living, thus, allow mosquitoes to breed in their own houses. So, it is now time for not only the people of Barguna but also the people of the whole country to become aware of the situation. Drinking water containers must be thoroughly cleaned with detergent powder at least twice a week and then water can be stored there again.
Areas around the houses where Aedes mosquitoes, Aedes albopictus and Aedes aegypti, can lay eggs should be destroyed. Units of the local government ministry such as municipalities, union councils, etc, discharge their duties properly. The people or entities responsible should regularly apply larvicides and adulticides. It has become essential to evaluate and monitor the application of larvicides and adulticides regularly in the morning and evening. A public awareness committee should be formed with prominent people of society and heads of various religious institutions to regularly monitor the situation. Young people are a key to social changes and they should be involved in such activities.
Inter-network should be established involving entities starting from the district administration to the union councils and dengue should be tackled by controlling Aedes mosquitoes in a coordinated manner. At the same time, it is important to take the same measures in other places. The effectiveness of conventional insecticides on mosquitoes should be tested by testing their active ingredients. In short, a crash programme should be run in the integrated pest management approach. Entomological advice is important in this work. Relief from this vulnerable situation can come only through the proper application of a sustainable method determined by experts.
It is always necessary to remember that this is a mosquito-borne disease. Instead of panicking, awareness and involvement are needed. It is necessary to focus on reality, not rumours. Barguna district covers an area of 1,831 square kilometres where only 10,10,000 people live. Given the expanse of the whole country, action should be commensurate to head off the spread of dengue.
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Professor Dr Md Golam Sharower is head of entomology at the National Institute of Preventive and Social Medicine, Dhaka.
