Controlling Dengue Using Bacteria

• 28 Aug 2020

Why in News

Researchers from the World Mosquito Program have used mosquitoes infected with Wolbachia bacteria to successfully control dengue in Yogyakarta city of Indonesia.

• The World Mosquito Program is an Australia-based not-for-profit initiative that exists to protect the global community from mosquito-borne diseases.

Wolbachia

• Wolbachia are natural bacteria present in up to 60% of insect species, including some mosquitoes.
• However, Wolbachia is not usually found in the Aedes aegypti mosquito, the primary species responsible for transmitting human viruses such as Zika, dengue, chikungunya and yellow fever.
• Wolbachia is safe for humans, animals and the environment.

Key Points

• About: The Aedes aegypti mosquito, that spreads Dengue and other diseases such as chikungunya, Zika and yellow fever cannot do so when they are artificially infected with a bacterium, Wolbachia.
  
  • The bacteria Wolbachia “inhibits” viral infection, that is, even if people encounter mosquito bite, they will not be infected. This happens because bacteria does not allow the virus to replicate in the mosquito thereby minimising its number within the mosquito.
• Method: The scientists infected some mosquitoes with Wolbachia and then released these in the city where they bred with local mosquitoes, until nearly all mosquitoes in the area were carrying Wolbachia bacteria. This is called the Population Replacement Strategy.
• Results: At the end of 27 months, the researchers found that the incidence of dengue was 77% lower in areas where Wolbachia-infected mosquitoes had been released, as compared to areas without such deployments.
  
  • This method does not only block Dengue Virus but also many other viruses present in mosquitoes.
• Mass Production: A French company InnovaFeed, which produces insects to feed livestock, is partnering with WMP to develop the first industrial-level production of Dengue- controlling mosquitoes.
• Other Developments: Indian Council of Medical Research (ICMR) also has been working on a similar project developing a strain of Aedes aegypti containing Wolbachia, known as Puducherry Strain.
  
  • The strain was developed at the Vector Control Research Centre (VCRC), Puducherry in collaboration with Monash University in Australia.

Dengue

• Dengue is a mosquito-borne tropical disease caused by the dengue virus (Genus Flavivirus), transmitted by several species of mosquito within the genus Aedes, principally Aedes aegypti.
• Symptoms include fever, headache, muscle and joint pains, and a characteristic skin rash.
• There are four strains from Type I-IV, of which Type-II and IV are considered more severe.
• Incidence of dengue has grown dramatically around the world in recent decades, with a vast majority of cases under-reported, according to the World Health Organization (WHO).
• WHO estimates 39 crore dengue virus infections per year, of which 9.6 crore show symptoms.
• India registered over 1 lakh dengue cases in 2018 and over 1.5 lakh cases in 2019, according to the National Vector-Borne Disease Control Programme (NVBDCP).
  
  • NVBDCP is the central nodal agency for prevention and control of six vector borne diseases i.e. Malaria, Dengue, Lymphatic Filariasis, Kala-azar, Japanese Encephalitis and Chikungunya in India. It works under the Ministry of Health and Family Welfare.
• The dengue vaccine CYD-TDV or Dengvaxia was approved by the US Food & Drug Administration in 2019, the first dengue vaccine to get the regulatory nod in the US.
  
  • Dengvaxia is basically a live, attenuated dengue virus which has to be administered in people of ages 9 to 16 who have laboratory-confirmed previous dengue infection and who live in endemic areas.

Source: IE