DENGUE CONTROL: THE UNREALISED PROMISE OF WOLBACHIA-INFECTED MOSQUITOES

Relevance:

  • GS 2 – Issues relating to development and management of Social Sector/Services relating to Health, Education, Human Resources.
  • GS 3 – Science and Technology- developments and their applications and effects in everyday life.

Why in the news?

  • Dengue, a well-known threat in India, imposes a substantial economic burden, with direct costs estimated at approximately ₹28,300 crore annually.
  • The impact of dengue also includes a loss of 5.68 lakh years of young life each year.
  • Reducing mosquito-borne illnesses through proven interventions can significantly alleviate the burden on health systems and boost productivity.
  • There is a need to revive and fund innovative vector control programs across India to tackle the Aedes-borne triple epidemic of dengue, chikungunya, and Zika.

DENGUE CONTROL: THE UNREALISED PROMISE OF WOLBACHIA-INFECTED MOSQUITOES - UPSC

The Vector control strategies

  • Current vector control strategies, such as insecticides and community education, have achieved only modest success.
  • Clinical trials have yet to establish the safety and efficacy of India’s two dengue vaccine candidates and identify effective antiviral agents.
  • Since a female Aedes mosquito transmits dengue, chikungunya, and Zika, biological vector control methods (e.g., sterile insect techniques) seem cost-effective, but their application is limited due to mixed results.

Innovative Vector Control Methods: The Wolbachia Approach

Innovative vector control methods using the Wolbachia bacterium have been studied globally since 2009.

  • Wolbachia in Insects: Wolbachia is a naturally occurring bacterium found in many insect species, such as fruit flies (Drosophila melanogaster), but not in Aedes mosquitoes.
  • Symbiotic Relationship: Wolbachia exhibits a symbiotic relationship with its host, displaying both mutualism (providing resistance to viral infections) and parasitism (shortening life span and skewing populations toward females).
  • Wolbachia Viral Resistance: Scientists observed that Wolbachia provides resistance to viral infections in fruit flies (mutualism) but also imposes a parasitic cost by shortening the host’s life span and skewing insect populations toward a female majority.
  • Resistance to viral infections may result from direct competition between the virus and Wolbachia for the host cell’s resources.

Research at the University of Queensland:

  • In 2009, McMeniman used the wMelPop strain of Wolbachia to reduce the lifespan of Aedes mosquitoes by half. In 2011, Walker and Johnson utilized the wMel strain to promote viral resistance without affecting the mosquito’s life span.
  • Promising Results: The wMel strain’s near-normal life span allowed more mating opportunities, rapidly establishing Wolbachia in mosquito populations, making it a promising candidate for blocking dengue transmission.
  • Field Trials and Clinical Studies: Following the initial successes, field trials and clinical studies were conducted, first in Australia and then across Oceania, Latin America, and Southeast Asia under the World Mosquito Program’s guidance.
Using wMel to Combat Dengue

Transinfection Process: Laboratory personnel mechanically transfer the wMel strain to the cytoplasm of embryos or adult mosquitoes, a process called transinfection. Once successful lines are established, these mosquitoes are released into urban areas.

Strategies for Dengue Control

Population Suppression – Singapore’s Approach:

  • Infected male mosquitoes (which don’t bite humans) are released into communities, covering 35% of households.
  • When these males mate with uninfected females, they produce non-viable eggs due to “cytoplasmic instability,” reducing the Aedes population by 90%.
  • Results: Singapore estimated a 77% reduction in dengue infection risk for people in the release areas.

Population Replacement – Australia’s Approach:

  • Infected mosquitoes are released over various population centers for 1-6 months.
  • Mechanism: Mating between infected and uninfected mosquitoes produces viable wMel-carrying offspring through maternal transmission.
  • Outcome: The wMel-Aedes mosquitoes became dominant in the wild, with no new releases required since 2017. Studies conducted seven years after the initial releases show a stable wMel genome, essential for continued success.
  • Results: Australia has reported successful outcomes in dengue control, approaching dengue elimination.

Randomized Controlled Trial (RCT) in Indonesia (2021)

  • In 2021, a groundbreaking randomized controlled trial (RCT) was conducted in Indonesia as part of a multi-national effort.
  • In this trial, wMel mosquitoes were released in 12 geographic regions, with 12 similar regions serving as no-release control areas.
  • Results: After three years, residents in the mosquito deployment areas were approximately 77% less likely to contract dengue. Additionally, these residents were 86% less likely to require hospitalization due to dengue.

Environmental and Safety Considerations:

  • Natural Occurrence: Wolbachia naturally occurs in 60% of insect species and does not infect humans or vertebrate animals.
  • Non-African Ecosystems: Aedes mosquitoes are relatively recent in non-African ecosystems, primarily due to the slave trade, global trade, travel, and rapid urbanization over the past 50 years.
  • Genetic Engineering: Scientists do not classify wMel transinfection as genetic engineering since it does not involve integrating the bacterium’s genome into the host’s genome.
Mel Programs in India

  • Global Dengue Burden: India contributes to a third of the global dengue burden.
  • Rising Dengue Cases: Dengue cases in India have increased more than fivefold, from 28,066 cases in 2010 to 157,315 cases in 2019, according to data from the National Vector Borne Disease Control Programme.
  • Economic Impact of Dengue Deaths: Dengue-related deaths are more expensive than severe hospitalized non-fatal dengue cases, with up to 90% of these costs being out-of-pocket expenditures, as reported in a study from Vellore (International Journal of Infectious Diseases, Vol. 84, July 2019).

Current Status:

  • India currently lacks an active wMel mosquito release program.
  • On July 5, 2022, the Indian Council of Medical Research — Vector Control Research Center (ICMR-VCRC) provided an update on developing two colonies of Puducherry wMel Aedes strains.
  • Since 2018, successful studies have been conducted, but government approvals are still pending.
  • Recently, ICMR reported the natural presence of Wolbachia in Aedes mosquitoes in Northeast India, though its significance remains unclear.

Implications for India:

  • The success of field trials and the Indonesian RCT underscores the potential benefits for India.
  • The wMel strategy could be highly cost-effective, especially in reducing the burden of other emerging infections like Zika, Japanese encephalitis, and chikungunya.
  • Given the challenges with insecticides—such as resistance, safety concerns, and limited effectiveness—the wMel strategy becomes increasingly important.
  • Public messaging about planned mosquito releases is crucial, especially in the era of social media and disinformation.
  • India can learn from the experiences of mosquito releases in cities across 14 different countries.

Way Forward for Dengue Control in India

  • Establish a Wolbachia Release Program: Initiate the development and implementation of a Wolbachia-infected mosquito release program across urban areas in India, focusing on regions with high dengue incidence.
  • Secure Government Approvals: Expedite the approval process for Wolbachia programs by engaging with policymakers and regulatory bodies to facilitate timely implementation.
  • Conduct Pilot Studies: Implement pilot projects in selected cities to assess the effectiveness and safety of Wolbachia mosquito releases before broader rollout.
  • Enhance Public Awareness: Develop comprehensive public messaging campaigns to educate communities about the benefits and safety of Wolbachia interventions, addressing potential concerns and misinformation.
  • Collaborate with International Partners: Leverage experiences and best practices from countries like Singapore, Australia, and Indonesia to inform program design and execution.
  • Monitor and Evaluate: Establish robust monitoring and evaluation frameworks to assess the impact of Wolbachia releases on dengue transmission rates and overall public health outcomes.
  • Integrate with Existing Health Systems: Ensure that Wolbachia programs are integrated into existing public health frameworks and vector control strategies to maximize effectiveness.
  • Invest in Research and Development: Support ongoing research to explore the potential of Wolbachia and other innovative vector control methods, including genetic engineering and other biological control strategies.
  • Address Environmental Considerations: Conduct environmental impact assessments to ensure that Wolbachia releases do not adversely affect local ecosystems.
  • Strengthen Healthcare Infrastructure: Enhance healthcare capabilities to manage potential increases in dengue cases during the transition to Wolbachia-based control methods.

Alternative articles

https://universalinstitutions.com/dengue-surge/

https://universalinstitutions.com/genetic-engineering-is-a-double-edged-sword-the-only-solution-is-to-accelerate-the-good-side-of-these-technologies-discuss-250-words/

Source: https://www.thehindu.com/sci-tech/health/dengue-control-the-unrealised-promise-of-wolbachia-infected-mosquitoes/article68519838.ece

Mains question

Discuss the economic burden of dengue-related deaths in India. Evaluate the effectiveness of current vector control interventions. How can innovative strategies improve outcomes? (250 words)