Dhaka North City introducing ‘Bti’ against Aedes, what will happen?

The expert opinion about eradicating Aedes mosquito, responsible for spreading dengue, is to strike on its breeding grounds first. But that does not seem to be happening that much.

Dhaka North City Corporation (DNCC) this time has brought Bacillus thuringiensis israelensis (Bti) to destroy the mosquito breeding grounds. This has been proven effective in many countries, said experts.  

Bti is a sort of bacteria which destroys mosquito larvae. One of its characteristics is that it does not have any side-effects on the human body. Not only that, it does not harm any other marine life either when applied on water. DNCC mayor Md Atiqul Islam told Prothom Alo last Thursday that the Bti is now waiting to be examined by customs at the port.

Dengue infection is seeing a huge rise in the capital and has spread to other parts of the country. The death toll is also increasing. While running the larvae survey at the beginning of the year, the health department had warned that dengue could increase at a massive rate this time. And that’s exactly what is happening in reality.

In context to the situation turning critical, Mushtaq Hossain of the Institute of Epidemiology, Disease Control and Research (IEDCR) said, “Measures that are taken to control epidemics should now be taken to control dengue also. Dengue has now turned into an emergency for public health in Bangladesh. Measures should be taken to control it. And, Aedes mosquito should be destroyed at the breeding source.”

The news of Bti being introduced came amid a dengue situation like this. And this news has comforted entomologists. Professor of zoology at Jahangirnagar University and entomologist Kabirul Bashar told Prothom Alo, “Bti has been proven effective in eradicating Aedes mosquitoes in many countries. Now DNCC has taken initiative to introduce it and that is certainly a good news.”

US’ Centers for Disease Control and Prevention (CDC) says that in case of an outbreak of a mosquito-borne disease, local government agencies take up extensive programmes for mosquito control. One of those is to apply Bti, which destroys the larvae. However, it cannot control grown-up mosquito. This bacterium is naturally produced right in the soil. It has been in use around the world for more than 30 years now.

Bti kills the larvae of mosquitoes, flies as well as other insects. Since it destroys the larvae, mosquitoes are reduced in number. And if mosquitoes cannot breed, it reduces the chances of chikungunya, yellow fever, dengue and zika outbreaks.

Entomologist Kabirul Bashar said that mosquito larvae consume crystals of this bacterium as food and it dissolves inside the larvae to produce a toxic substance, which kills the larvae. And, if these dead larvae are consumed by the living ones, eventually it will kill them as well. In this way, the life cycle of the larvae will automatically be destroyed.

According to CDC data, Bti is found in different formulation like pills, liquid, lump, powder etc. It can be applied to the water accumulated at any spot, water stored in different containers, pond, sewer, drain, marsh or any other places. This larvae-repellent can be spread through vehicles, airplanes or hand pumped spray machines.

As per US’ Environmental Protection Agency (EPA) data, it’s neither harmful for the environment, nor it causes any harm to humans, pet or other animals, marine lives and bees.

This pesticide is EPA-approved. The effectiveness and safety of the pesticides, approved by this agency, are proven through research. Bti being sprayed in a residential or any other wide-spread area from trucks or from the sky has been proven to be safe.

Apart from residential areas, it is also used in commercial and agricultural areas. It is also used in organic farming. Bti can also be applied to frozen water, following user guidelines, where mosquitoes can lay eggs. But, its application does not cause any damage to food grains or water.

CDC considers Bti to be the most effective method when it comes to coordinated mosquito management. Till now, Kolkata City Corporation has achieved significant success in preventing Aedes mosquito from breeding and in dengue control. Their coordinated mosquito control programme has been proved to be highly effective.

Kolkata Municipal Corporation’s chief vector control officer Debashish Biswas told Prothom Alo that Bti is being used to control the spread of Aedes in Kolkata since 1996. It has been proved quite effective. Till last Saturday, only 160 dengue patient had been identified in the state, he added.

DNCC is importing Bti in powder formulation. Meanwhile, the decision of using Bti on an experimental basis was taken based on the decision of Dhaka South City Corporation (DSCC)’s committee on the selection of insecticide to be used for mosquito control, coming from their meetings held on 11 October, 2021 and 5 February, 2023. But they did not initiate any procedure for the purchase of that. DSCC uses an insecticide named Temifs to kill dengue larvae.

Chief health officer (in-charge) at DSCC, Fazle Shamsul Kabir told Prothom Alo, “Temifs have been proved to be effective enough. We are not thinking of changing this at the moment. Every organisation does have their own work strategy. DNCC wants to use Bti, that’s their decision. We have our own technical committee. If they recommend any alternatives in future, we’ll decide about that.”

When asked, “If Bti is used only in one of the two adjoining cities, how effective will the mosquito control of Dhaka be?” entomologist Kabirul Bashar said that it is only natural that every organisation will work according to its own ideologies and plans. But, it’s better to use pesticides that are more effective and environment-friendly with lesser health risks.