Researchers carrying out studies on the Knock Down Resistance (KDR) have found that people in north Bengal are not very well aware of the Aedes mosquito habitats and their possible dangerous outcome in the dengue scenario.

The virus is transmitted to humans through bites of the Aedes mosquito, namely Aedes aegypti and Aedes albopictus. Insect biologist Dr Dhiraj Saha is leading the studies, along with scholar Dr Minu Bharati, the assistant professor of the SBS Government College, Hili, in north Bengal districts from November 2019.

The three-year-long research is based on sampling of the pupa and larvae, and conversion of the adult mosquito in laboratories.

“Dengue virus is one of the most dreadful human pathogens and it has been a regular phenomenon in India. We are conducting the study from November, last year and it has been found that most of the people here are not much aware of the habitats of the Aedes mosquito, and these issues are not addressed. Mass awareness is inevitable in proper prevention of this disease. Larval habitat destruction is the first and safest method of dengue prevention,” Dr Saha said.

The survey also cautions that continuous and unchecked usage of insecticides might give rise to insecticide resistance in target mosquitoes, hence giving rise to failure in mosquito control programmes.

Explaining the KDR, Dr Saha said it is a strategy where insects survive in an environment of regular exposure to insecticide. This reduces the efficacy of the insecticide, and is a mechanism to survive and is called target site resistance or KDR, according to him.

North Bengal, due to its high rainfall, humid temperature, and high vegetation cover provides an ideal environment for the Aedes mosquito, and thus the associated diseases, experts have said.

Additionally, the high population density, along with lack of awareness among the people on the disease, triggers ‘efficient circulation of the disease’, the survey so far has found.

“Simply changing minor practices might help prevent dengue to a great extent. Many mosquito breeding habitats have been recognised in the northern districts of West Bengal. The most common being cemented tanks and discarded tyres. Cemented tanks are basically used in motor garages to check tyre leaks. The water in the tank is neither regularly changed nor treated, thus attracting female Aedes mosquito to lay eggs and hence converting it into a mosquito breeding habitat.

In north Bengal, discarded tyres are generally not properly disposed of, rather these are stacked together and kept out in the open.

These tyres, after they get filled with rainwater, serve as efficient mosquito breeding habitats. Rainwater fills all the possible mosquito breeding habitats, such as tree holes, artificial containers, coconut shells, even dried leaves.

Thus, with the arrival of the monsoon, cases of dengue see a spike until winter, when water in different habitat dries up,” the researchers said. Dr Saha, who is also the head of the Department of Zoology at the North Bengal University, said that throughout the districts of north Bengal, resistance against commonly-used insecticides had been documented in research articles.

“More than one mechanism has been shown to confer such resistance. Both metabolic resistance and target site resistance are common in mosquitoes collected from north Bengal,” he said.

More than 1 lakh cases of dengue are reported every year in India. In 2017, among the Indian states, the highest number of dengue infections was reported in West Bengal.

The study has stressed that climatic conditions play a vital role in the transmission rate of dengue infections.

“Therefore, during this coronavirus pandemic, immediate measures should be taken for proper prevention of dengue and to reduce the menace of this viral disease. As initial symptoms of viral diseases are similar, extra caution should be paid to these diseases and their management,” Dr Saha said.