Dengue menace: We need entomologists to introduce vector management system

We all know that dengue is a vector-borne disease, and the Aedes mosquito spreads it. Other than dengue, it also spreads diseases like Zika and Chikungunya. But what we do not know is that dengue is the most transmitted disease in this world. 

Every year, 5 to 20 crore people get infected by dengue. More than 100 countries are struck by it. In the last few years, it spread rapidly because of our growing worldwide movement.

But that is not the only reason. 

In our country, unplanned construction, waste disposal systems, and climate change are the most prominent reasons for the fast spread of dengue infection. Also, our vector control system is not quite up to date either. Rather, in the 1950s, this measure was way stricter, and we also used to spray strong insecticides. Until 1970, there were not many cases of dengue.

However, in 2000, dengue took a dangerous turn when we reported 6,000 dengue patients for the first time. After that, the numbers were like a rollercoaster – sometimes noticeable, sometimes average, but never less than 300. 

From 2014, the second phase began, and the numbers gradually started jumping. And in 2018, we saw a spike. For this growth, I blame our deadly combination of humidity, temperature and excessive rainfall. There is no doubt that these three components have helped to increase the growth of dengue. 

Dengue virus causes dengue fever. It has four serotypes titled DENV 1,2,3, and 4. These serotypes have an interesting feature that when you are affected by one of them, your body grows an immunity against that. 

But the twist is that it makes you more fragile to the other serotypes and increases your chances of the severity of the disease. In recent years, we have observed more cases of this severity of the disease.

In 2020, we found all four serotype patients. This is an alarming situation because it automatically increases the chances of complications for patients. On the other hand, it puts children in the danger zone as they do not have any protection against the serotypes. That is why, over the past few years, we have received more children than adults as patients.

Now, the question is, what can we do to control this situation? 

According to the World Health Organisation (WHO), we must think about a global vector control response strategy. If we can plan this properly, we might be able to control dengue. So, under this global vector control response, we can introduce an integrated vector management system for us. There will be two parts: technical and management. We will look after Aedes mosquitoes' breeding source, larval control and adult control in these two parts.

Now, the breeding source is directly connected to our urban plan. The more we urbanise, the more we use plastic containers, tires and construct new buildings. Unfortunately, the rapid growth is uncontrollable, and so is Aedes's breeding source, as we remain unaware. 

But the alarming thing is we have exposed our rural areas too. Since irregular rainfall has been added to this list, the situation has become more acute, which is reflected in the past few years' infection rates.

To decrease the infection rate, we need to reconsider our vector control measurements. But to observe those, what do we need? Entomologists. Now the question is, how many do we have? 

We have fewer than ten entomologists when we require hundreds of entomologists only for  Dhaka city. We must have at least one entomologist at each ward. Also, institutions and training centres for research purposes are essential.

Sadly, we depend more on mosquito extermination employees, who do not understand anything and follow the rules blindly. Without understanding the life cycle of Aedes, we cannot fight dengue, but we are doing exactly that. 

As we are ignoring the entomological part, automatically, the insecticide part is being discounted. And corruption is playing a vital role in this system. The workers cannot verify whether the original insecticide is used as we lack laboratories. So, we are just fogging, but the result is zero – both in knockdown and mortality rate. 

On top of that, our current system is not working because there is no community engagement. How do we expect to take care of such a dangerous disease through some day labourer who lacks proper training? 

I am proposing to our city corporations to recruit entomologists. It will be easier to conduct surveys on all the indexes like abandoned containers, breeding sources, and adult density of Aedes mosquitoes. This way, we would be able to plan on how much we need to depend on insecticide. 

The other thing I propose is to introduce community engagement. The landlord, ward counselor, and community leaders should be in charge of their area and clean it. 

Last but not least, we must not forget to implement our law: The Infectious Diseases (Prevention, Control and Eradication) Act 2018.

But in the long run, we should think of different strategies. Maybe, we can build a team of entomologists and take strategies for dengue prevention and control under the local government, for five to 10 years. 

We will include the Ministry of Environment, Forest and Climate Change, Ministry of Health and Family Welfare, and Ministry of Religious Affairs. We need to plan for a greener, cleaner, and pollution-less city, where anything against the environment will be banned for vector control.

In Singapore, dengue is known as an environmental disease, and they have been successful in decreasing it tenfold, following the methods that I have mentioned. We can also follow these environmental management methods as the dominant vector control strategy.

Be-Nazir Ahmed, Former Director of Disease Control at Directorate General of Health Services. Illustration: TBS

Dr Be-Nazir Ahmed is a former director of Disease Control at the Directorate General of Health Services.