Many infectious diseases are transmitted via an obligatory insect vector host for the successful completion of the pathogen’s life cycle. Managing vector-borne diseases thus involves dealing with a triad of players – the human host, the pathogen, and the vector. Mosquitoes are one such critical vector, involved in the transmission of a large number of diseases. We use evidence-based understanding of the behaviour, biology, and ecology of mosquitoes to develop better, more specific, and ecologically responsible means of controlling them.
We have designed a multi-tiered approach to this challenging problem. The first tier is environmental engineering; what environmental features support and sustain or deter mosquito populations at the larval and adult stages. In the second approach, we seek to improve methods that reduce mosquito-human encounters. For this, we use knowledge of the chemical ecology of mosquitoes and tap into traditional deterrents to identify novel compounds. Finally, we seek to use specific molecular knowledge of mosquito species to intervene in their behaviour, particularly the host seeking and mating behaviours. We apply both modern and traditional knowledge in this context to develop specific and ecologically responsible interventions.
Dengue is an annual epidemic in India. In 2019, the dengue burden in India peaked at about 1,57,315 cases and Karnataka recorded 16,986 cases. Of these, Bengaluru contributed ~50% (9,029) of dengue cases (National Centre for Vector Borne Diseases Control; NCVBDC). Like many cities, in Bengaluru, Aedes population surveillance primarily involves indoor larval surveillance as per WHO protocols to measure house index, container index and Breteau index to quantify the disease risk in a specific residential area. Source reduction (emptying water holding containers), anti-larval spraying, and providing health education/awareness are the main intervention strategies for Aedes control. The areas with highest house indices and larval counts are considered as productive. These indices record relative larval abundance in a locality for a specific period with no correlation with adult abundance and without regard for seasonal fluctuation in larval abundance. Furthermore, entomological surveys are often biased towards locations or houses with high mosquito densities or disease outbreaks.
Aedes-borne disease risk is associated with contemporary urbanization practices where city developing structures function as a catalyst for creating mosquito breeding habitats. We lack better understanding on how the links between landscape ecology and urban geography contribute to the prevalence and abundance of mosquito and pathogen spread. In this longitudinal study conducted during the COVID-19 pandemic period, we quantify the mosquito larval habitat across a gradient of urban landscape.
Investigator: Farah Ishtiaq
Brhuat Bengaluru Mahanagara Palike (BBMP), Bengaluru
Mosquitoes act as vector for spread of deadly diseases such as malaria, dengue, Zika, and chikungunya. Current methods of controlling mosquito populations for control of diseases include use of insecticide spraying, insecticide-impregnated nets and use of chemical mosquito repellents. Escalating resistance to available insecticides demands a need for novel approaches for vector control. Most of the effective repellents available in the market are costly and have side effects like asthma, cough, headache, eye irritation, etc.
We aim to identify novel mosquito attractants and repellents from plants and animals. Our priority will be to screen plants mentioned as potential mosquito repellents in traditional knowledge of different cultures. Dual choice olfactometer, wind tunnel assays, and methods like chemical fractionation, and electrophysiology will be used to find better safer, and eco-friendly mosquito repellents.
Investigator: Jay Prakash Shukla
CSIR-Central Institute of Medicinal and Aromatic Plants (CIMAP), Lucknow
Mosquitoes, both male and female, usually feed on carbohydrate-rich sources of nectar or sap. Occasionally, the female switches to taking a blood meal. This dramatic change in dietary preference is essential for the development of her eggs. Because of this, female mosquitoes of some species have become important vectors of infectious diseases such as Malaria, Dengue and Chikungunya. Interfering with the molecules that drive this change in dietary preference will be an effective way of abrogating blood-feeding behaviour and therefore disease transmission.
Many behavioural studies report that Aedes aegypti females need to mate to develop an appetite for blood. Once blood-fed, however, they suppress this appetite until their eggs are laid. In contrast, we find that virgin female Anopheles stephensi – the major vector for malaria in urban India – have a robust blood appetite that is sustained even after blood-meals. This has implications for vector control strategies that seek to interfere with mating to curb vector-borne diseases. While such strategies may be effective for Aedes species, they will likely increase disease transmission through Anopheles species.
We have looked at gene expression changes in the brain across these behavioural states to identify candidates that might promote or suppress blood-feeding. We are also developing cheaper alternatives to single cell transcriptomics for the Indian research and biomedical community, and have standardised methods that enable single cell transcriptomics to be performed on fixed tissue samples. We have promising candidates that are now being validated through RNA interference. These will be useful targets for developing small molecule interventions for blood-feeding.
Investigator: Sonia Sen