India needs more entomologists

With global warming and climate change, the surge in dengue cases has been dominating the news. It’s logical that these issues are discussed together, as they are deeply linked. The shift in climatic conditions is enabling dengue to spread to previously unaffected areas, infecting an increasing number of people. The only effective means of shielding ourselves from this escalating threat is through decisive public health action. These measures against mosquitoes and other disease vectors include fogging, inspecting buildings for stagnant water, applying larvicides, and guiding people on personal protection. To understand the spectrum of vector-borne diseases, both old and new, and to develop control strategies, we need a cadre of public health entomologists.

Medical entomology, a crucial and fairly complex field within preventive healthcare, deals with disease-transmitting insects, known as vectors, responsible for spreading diseases like malaria, lymphatic filariasis (LF), elephantiasis, and kala-azar, all of which have a significant impact on lives and livelihoods. Newly detected infections like zika (transmitted by the same species of mosquito as dengue) and others like scrub typhus, transmitted by a mite, largely go undiagnosed in India. It is imperative that we no longer neglect this field.

Amid challenges like climate change affecting mosquito behaviour and insecticide resistance, entomology is crucial for disease elimination. While advanced diagnostics and treatments are essential, understanding disease patterns and vector behaviour is vital for prevention. Entomologists provide valuable insights into changing insect behaviour, species variants and genetic changes, and locating breeding grounds—critical considerations for disease elimination efforts.

Entomology has played a pivotal role in reducing the burden of kala-azar and LF. The impact of this is evident in the decline of kala-azar, transmitted through sandfly bites, with cases dropping from 157 per 10,000 in 2014 to zero in 2023, nearing its elimination. Similarly, for LF, a debilitating mosquito-borne disease, transmission has decreased, with 101 out of 333 high-burden districts achieving infection levels below the target threshold.

In the kala-azar programme, entomologists played a vital role, developing strategies to curb sandfly populations and addressing insecticide resistance. LF Transmission Assessment Surveys (TAS), which involve testing at-risk populations for filarial antigens to determine the levels of infection in a given population, were critical for developing subsequent strategies. Recognising that early detection and prompt treatment are crucial, India has focused on enhancing the accessibility and quality of diagnostic tools and therapies in underserved areas. Mobile clinics,
community health workers, and telemedicine initiatives have brought healthcare
services closer to vulnerable populations.

However, while celebrating these successes, significant challenges persist—challenges that can be addressed through entomology. A worrying increase in dengue cases has been recorded in recent years. Factors such as urbanisation, inadequate water and waste management contribute
to the breeding of Aedes mosquitoes, the primary vectors
for dengue. This is where entomologists come in. By mapping disease hotspots, entomologists assist in evaluating control measures, developing targeted interventions, and determining resource allocation.

Rising temperatures, increased rainfall, and changing ecological conditions have expanded the geographic range of insects, allowing them to thrive in regions where they were previously absent. Through research and surveillance, public health entomologists can address threats using cutting-edge research in genomics to understand insects’ disease-transmission abilities. For example, the Tata Institute for Genetics and Society, Bengaluru, identified genetic mutations linked to insecticide resistance in mosquitoes, paving the way for improved vector control strategies. Other methods, like the sterile insect technique, Wolbachia infection of mosquitoes, and genetic manipulations, including gene drive technology, are being tested in different species of mosquitoes to prevent disease transmission.

Currently, there are not nearly as many public health entomologists engaged with state governments and municipalities as there should be. Given the critical role they play in public health, there should be at least one entomologist in every district. ICMR has now increased their capacity for public health entomologist training to about 70 per year, and medical colleges must follow suit. Without their expertise, tailored interventions, early detection, and rapid response to vector-borne disease outbreaks will not be possible. Entomologists’ inputs are crucial for safeguarding the health of our communities.

(The writer is the chairperson of the M S Swaminathan Research Foundation and a former chief scientist at WHO)