‘Inadequate action plan to worsen dengue situation this year’

Dr Kabirul Bashar is a professor of the zoology department at Jahangirnagar University, and a renowned medical entomologist and scientist. He is also a popular public speaker on dengue, chikungunya, malaria, and filariasis in Bangladesh.

He is working as an international exchange adviser and collaborative professor at Kanazawa University of Japan. Dr Bashar serves as the consultant to the Global Fund, National Malaria and Dengue Control Programme, and several other multinational companies.

The professor is an editorial board member of many international journals. Kamran Siddiqui of The Business Standard interviewed him recently on the mosquito control situation in Bangladesh.

Why did you choose mosquitoes as your work domain?

I started my career in 2000 at the then Dhaka City Corporation (DCC). During my work there, I found that mosquitoes were a severe problem in Bangladesh, and realised the necessity of an expert in the mosquito control field. After that, I chose the subject of my research.

In 2009, I received three scholarships for my PhD and chose the topic of mosquito research in Japan. Since 2000, I have been working on that tiny deadly insect which is of great importance to public health.

How many mosquito species are found in Bangladesh and how many of them spread diseases?

A total of 123 mosquito species were recorded by various scientists from Bangladesh at different times. Among those, 22 species have the record of transmitting diseases in the Southeast Asian region.

When was the first dengue case found in Bangladesh?

A dengue case was first identified in Dhaka in 1964, and at that time it was called the "Dhaka Fever". In 2000, a mass spread of dengue occurred in Dhaka, infecting a total of 5,500 people and killing 93, according to the Directorate General of Health Services (DGHS).

Since then, the disease appeared more or less every year in Dhaka. Unfortunately in 2019, dengue spread all over Bangladesh in both urban and rural areas, infecting more than 1 lakh people and killing 156.

Which mosquito species are dengue vectors?

Two species of Aedes mosquitoes, Aedes aegypti and Aedes albopictus, are the vectors of dengue, chikungunya, and zika across the world.

Aedes aegypti is the primary vector and albopictus is the secondary vector. These two species are transmitting dengue in Bangladesh.

How can people recognise these two species?

Both the species have white spots on their bodies and legs. Aedes aegypti is considered as a domestic mosquito, which prefers to stay near human residences. It is also known as the urban mosquito. They breed or lay their eggs in artificial water containers.

After a survey and research conducted in different areas of Dhaka, we have observed that Aedes mosquitoes have a good connection with unplanned urbanisation.

Meanwhile, the albopictus mosquitoes like to live in rural areas, especially outside of the house. They like forests and vegetation. They breed in natural containers such as bamboo stumps, leaf axils and tree holes. This species is also known as the Asian tiger mosquito.

Dengue spread widely all over the county last year and chikungunya also spread 2 years ago. Why did we fail to control the mosquito population?

Aedes mosquito has an interesting characteristic. Their egg is like the seed of paddy, which can survive for 6-12 months in a dry condition. Dengue spread over the country at a very large scale last year and chikungunya's spread was high in 2017.

We had predicted the issue in February last year. We needed to implement an Integrated Mosquito Management plan to control Aedes mosquito population before the spread of these diseases.

I had learnt that manpower is scarce for mosquito control in both Dhaka North and South city corporations. They do not have an expert – medical entomologist – for mosquito control.

Every mosquito has its specific nature and breeding habits, and target-specific control measure is required for each species. Mosquito control is a science and it should be managed scientifically with the suggestion of experts.

How do you evaluate the capacity and measures of Dhaka city corporations to control mosquito?

The city corporations are the main driving force in mosquito control. An entomologist is necessary to control the mosquito population. But the authorities do not have any. Moreover, they do not even have sufficient manpower for mosquito control.

They should have a strong action plan regarding Culex and Aedes mosquitoes. Both Dhaka North and Dhaka South called me several times. We have given our suggestions regarding the management of both genera.

However, they have informed me about a lot of limitations.

The city corporations have a mosquito control programme with a special focus on Culex. The species is born in drains, small water bodies, and dirty water. But Aedes is not like that. So, the controlling system of both will not be the same.

Besides, most of the spray-men of the city corporations are elderly people. They spray the medicine on the road and outside of homes through a fogger machine. But Aedes do not stay on the roadside normally. So, the spray-men need to be trained regarding Aedes control.

Are there any comprehensive measures to control mosquito populations in Bangladesh?

In Bangladesh, we are not controlling mosquitoes through comprehensive measures or integrated vector control methods, but we need to implement those methods.

What will be the dengue situation in 2020?

The dengue cases in January 2020 are higher than that of the previous year. Therefore, we can predict that the dengue situation will worsen this year if the year-round dengue management action plan is not implemented.

So, I requested both the city corporations to start the Integrated Vector Management action from March 2020.

What is your suggestion for this year's dengue management?

The Integrated Vector Management is a rational decision-making process that seeks to optimise the use of resources in vector control.

Its purpose is to improve the effectiveness and achieve sustainability in vector prevention and control activities, which includes processes such as the selection of methods based on knowledge of biology, disease transmission and morbidity, and the use of multiple interventions, often combined in a synergistic and synchronised fashion.

Other processes are: a collaboration of the health sector with other public and private sectors related to the environment, whose mandate influences or can influence vector reduction; and engaging and mobilising communities.

Integration of families and other key partners (such as education and finance), the establishment of a legal framework to underpin an integrated, inter-sectoral approach, and capacity building are also necessary processes for vector prevention and control activities.

Tell us about mosquito control insecticides.

Insecticides are a quick and powerful way to get rid of mosquitoes around the yard, but unfortunately, they are only temporary. The effect usually lasts only as long as the insecticide is present.

So, as soon as it drifts away or dries out, mosquitoes return.

There are a variety of products available on the market for mosquito control. Insect Growth Regulator, and larvicides are chemicals designed to be applied directly to water to control mosquito larvae.

Adulticides are used in fogging and spraying to control adult mosquitoes. Synergists can be mixed with insecticides, which are not toxic to the mosquitoes themselves, but they make adulticides more effective. The selection of proper insecticides is the key requirement for mosquito control.

Over time and through repeated use, insecticide resistance can occur in mosquito populations. The ability of mosquitoes to resist insecticides represents a serious threat to the prevention of diseases such as malaria, dengue and chikungunya, and will threaten efforts to prevent epidemics.