GENETIC MANIPULATION OF MOSQUITOES

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Context

• The fight against mosquito-borne diseases enters a new era as genetic engineering gives mosquito control an upgrade.

Details

The Ongoing Battle Against Mosquitoes

• Throughout the annals of human history, mosquitoes have persistently buzzed in the background of human existence, presenting a dual challenge of irritation with their relentless bites and peril through the transmission of deadly diseases.

A Long-Standing Problem

• The earliest evidence of mosquitoes dates back at least 70 million years, with Egyptian mummies from 2000 BC bearing testimony to the ancient existence of mosquito-borne diseases like malaria.

A Multitude of Diseases

• Beyond the specter of malaria, which claims the lives of over half a million people every year and afflicts nearly 250 million, mosquitoes act as vectors for a diverse array of diseases.
• These include dengue, Zika, lymphatic filariasis, and yellow fever. Understandably, our relationship with these diminutive, bloodsucking insects has been fraught with hostility.

Challenges in Mosquito Control

Urbanization and Disease Surges

• The rapid urbanization of the world's population, particularly in burgeoning economies like India, has engendered annual surges in mosquito-borne illnesses, most notably dengue.

Insecticide Resistance

• Coupled with the looming specter of climate change and its far-reaching consequences, mosquito-borne diseases have expanded into new territories.
• Notably, indigenous cases of dengue have emerged in France in recent years.

The Role of Existing Control Methods

• In the relentless battle against mosquitoes, a plethora of tools has been deployed, ranging from mosquito nets to insecticides and the strategic use of symbionts like Wolbachia.

Genetic Manipulation of Mosquitoes

Unlocking Genetic Potential

• In the past two decades, advances in genomic sequencing techniques have equipped us with the ability to decode and manipulate the genetic makeup of organisms, furnishing us with innovative tools to combat mosquito-borne diseases.

Reference Genomes for Anopheles stephensi

• Progress in next-generation sequencing techniques has provided us with comprehensive genome sequences for numerous mosquito species.
• Notably, researchers from the University of California, the Tata Institute of Genetics and Society, and the Institute of Bioinformatics and Applied Biotechnology have played pivotal roles in constructing high-quality reference genomes for Anopheles stephensi, a primary malaria-vector mosquito.

Gene Drive Technology

Revolutionizing Control

• The cornerstone of genetic mosquito manipulation is the systematic control of mosquito populations by interfering with their reproductive mechanisms.
• Researchers worldwide have devised various genetic modification strategies to achieve this, with one of the most significant innovations being gene-drive technology.

The Pioneering Work of Austin Burt

• This groundbreaking technology originated with the work of Austin Burt, a professor at Imperial College London, who introduced it in a 2003 paper published in Royal Society Proceedings.
• Gene-drive technology operates by having a protein cut the mosquito's DNA at a site that does not encode a specific genetic sequence in the genome.
• This initiates a natural cellular mechanism to repair the DNA, compelling the cell to incorporate a sequence known as the "drive sequence" into the damaged portion.

Disrupting Malaria Transmission

• Numerous versions of gene-drive technology have emerged in scientific literature, all focused on reducing mosquito populations' reproductive capabilities or rendering them sterile.
• This, in turn, hinders the malaria parasite's ability to replicate within the mosquito's gut.
• A recent paper in Science Advances highlights the successful genetic enhancement of a gene expressed in the midgut of mosquitoes to produce two antimicrobial substances, magainin 2 and melittin.
• These substances are detrimental to the development of the Plasmodium parasite in the mosquito's midgut and also reduce the lifespan of female mosquitoes.
• Computational models suggest that this approach could significantly disrupt malaria transmission.

Real-World Applications

Genetically Modified Mosquitoes in the U.S.

• In 2020, the S. Environmental Protection Agency granted authorization for the release of genetically modified mosquitoes called OX5034 in counties in Florida and Texas.
• Developed by Oxitec, these mosquitoes carry a gene sensitive to an antibiotic, tetracycline. Extensive field trials conducted by the company in Brazil preceded this authorization.
• Genetically modified male OX5034 mosquitoes mate with female mosquitoes, but the self-limiting gene prevents female offspring from surviving.
• Consequently, male mosquitoes disappear from the environment after approximately a dozen generations.

Positive Outcomes in Trials

• Similar trials involving genetically modified mosquitoes have been conducted in India, Brazil, and Panama under outdoor but controlled conditions.
• Early results from these trials demonstrated substantial reductions in mosquito populations, with a staggering 90% decline observed during the trials.
• Further trials have indicated that these technologies can significantly decrease the incidence of dengue.

Benefits and Risks

• These innovative technologies hold the promise of mitigating the threats posed by mosquitoes. However, they also introduce a set of benefits and risks.

The Ecological Impact and Unknown Consequences

• An immediate implication is that the drastic reduction in the mosquito population could disrupt food chains and ecosystems that depend on mosquitoes.
• It is plausible that other mosquito species or insects could fill the ecological void left behind.
• The long-term and short-term consequences of such disruptions remain uncertain, posing a challenge for policymakers.

Challenges and Concerns

Multifaceted Challenges

• The genetic engineering of mosquitoes and trials involving genetically modified mosquitoes have encountered multifaceted challenges in different parts of the world.

Valid Concerns

• Critics have voiced valid concerns regarding unintended consequences, including unforeseen ecological disruptions and the potential for engineered genes to spread beyond targeted mosquito populations.

Regulatory Guidelines

In response to these challenges, the Department of Biotechnology recently released comprehensive guidelines for genetically engineered insects. These guidelines outline procedures and regulations for researchers working with such insects in the country.

Conclusion

The enduring struggle between mosquitoes and humankind serves as a testament to human ingenuity in our fight against vexing adversaries shaped by evolution. As we navigate the complexities of genetic engineering and its impact on ecosystems, we must tread carefully, acknowledging the profound implications and uncertainties that accompany this groundbreaking technology. The balance between eradicating mosquito-borne diseases and preserving ecological equilibrium remains a pressing concern, one that demands careful consideration and responsible decision-making.

PRACTICE QUESTION Q. Explain the concept of gene-drive technology and its potential applications in mosquito population control. Discuss the key principles and ethical considerations associated with this technology. (250 Words)

https://www.thehindu.com/sci-tech/science/mosquito-control-gene-drive-technology-benefits-risks/article67287784.ece