Context: With insecticide resistance in mosquitoes rising to alarming proportions, it has become imperative that newer approaches to mosquito control gain prominence. Gene-drive technology is one such approach, which has been used in outdoor trials in India, Brazil, and Panama.

Background:

• Mosquitoes are insects that are known to transmit or serve as vectors for deadly diseases like dengue, malaria, Zika, lymphatic filariasis, and yellow fever.
• The earliest known mosquitoes from the fossil record date back at least 70 million years, and evidence of mosquito-borne diseases like malaria dates back to Egyptian mummies from 2000 BC.
• The rapid urbanisation of the world’s population has led to annual surges in mosquito-borne illnesses like dengue. Coupled with climate change, the mosquito-borne diseases have expanded into new territories. E.g., Indigenous cases of dengue in France in recent years.

Restraining Mosquito Population with CRISPR:

• Using genome sequencing techniques, scientists have access to the whole genome sequences of multiple mosquito species.
• They have created a system that restrains populations of mosquitoes by leveraging advancements in Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) – based genetic engineering.

1. Gene drive technology:

• Gene drive is a type of genetic engineering technique that can permanently change the traits of a population or even an entire species so that they do not follow the typical rules of heredity.
• Gene drives are genetic elements that pass from parents to unusually high numbers of their offspring, thereby spreading quickly. Gene drives occur naturally but can also be engineered.

How does it work?

• The gene drive technology is designed to introduce a genetic tweak in the population of a species by altering the rules of inheritance from parent to offspring.
• Firstly, using the CRISPR gene editing tool, a gene called ‘doublesex’ in female mosquitoes is disrupted. 
• This genetic tweak of the double-sex gene follows gene drive inheritance. Here, the gene drive inheritance makes the female mosquitoes inherit two copies of the disrupted gene.
• When the female mosquitoes inherit two copies of the disrupted gene, they develop like males and are unable to bite or lay eggs.
• Unable to bite, those mosquitoes can not transmit malaria-causing parasites from their bodies to humans.

2. precision-guide Sterile Insect Technique (pgSIT): 

• Sterile Insect Technique is an environmentally safe and proven technology to suppress wild populations.
  • Males do not transmit diseases, so the idea is to release more and more sterile males.
  • The population of mosquitos can be suppressed without relying on harmful chemicals and insecticides. 

• To further advance its utility, a novel CRISPR-based technology, termed precision-guide Sterile Insect Technique (pgSIT) is described. pgSIT is a new scalable genetic control system that uses a CRISPR-based approach to engineer deployable mosquitoes that can suppress populations.
• It alters genes linked to male fertility—creating sterile offspring—and female flight in Aedes aegypti, the mosquito species responsible for spreading diseases including dengue fever and chikungunya. 
• pgSIT mechanistically relies on a dominant genetic technology that enables simultaneous sexing and sterilization, facilitating the release of eggs into the environment and ensuring only sterile adult males emerge. The system is self-limiting and is not predicted to persist or spread in the environment.
• pgSIT eggs can be shipped to a location threatened by mosquito-borne disease or developed at an on-site facility that could produce the eggs for nearby deployment.
• Once the pgSIT eggs are released in the wild, sterile pgSIT males will emerge and eventually mate with females, driving down the wild population as needed.

Associated Risks:

• Drastic reduction in the mosquito population could alter food chains and ecosystems that involve mosquitoes. So, it is likely that the gap in the food chain could be ‘invaded’ by other mosquitoes or other insects.
• Other unintended consequences can be unforeseen ecological disruptions or the potential for engineered genes to spread beyond target mosquito populations.

Hence, some of these concerns are valid and require extensive data collection, close monitoring, and multistakeholder discussions surrounding the adoption of these technologies.