Wolbachia emerges as an alternative strategy against dengue

The bacterium can block virus in Aedes (Dengue, zika and chikungunya-causing) mosquitoes from replicating

By   |  Published: 9th Dec 2019  12:17 amUpdated: 9th Dec 2019  1:17 am
Mosquito breeding is so intense that even during dry season like winter, authorities continue to employ traditional methods such as fogging. — File photo

Hyderabad: A commonly occurring bacterium Wolbachia has emerged as a possible alternative strategy to stop rampant breeding of Aedes aegypti mosquito and check dengue in India.

The recent scientific development concerning Wolbachia has relevance in Telangana where public healthcare systems and entomologists from the municipal wings received a lot of flak for struggling to check mosquito breeding, which led to dengue outbreak in Hyderabad between July and August.

The menace of Aedes aegypti (which causes dengue) and Aedes albopictus (which causes chikungunya) breeding is so intense that even during dry season like winter, the public health institutions and municipal sanitation wing continue to employ traditional methods such as fogging and releasing of oil balls, comprising husk, sand and oil, for one-time kill of mosquitoes in water bodies.

What is Wolbachia and how it can help?

Wolbachia is a commonly occurring bacterium that infects 60 per cent of insect species. Researchers, however, have figured out that it does not harm the Aedes mosquitoes but can block virus in them from replicating, which reduces the risk of transmission of dengue and other viral diseases such as zika and chikungunya when they bite.

This means that Wolbachia-infected mosquitoes are unable to transmit viruses such as dengue, zika, chikungunya and yellow fever. Moreover, when they breed, they pass-on the bacteria to the offspring, which means the viral diseases such as dengue etc are not transmitted by subsequent generations of Aedes.

Field trials

The World Mosquito Program (WMP), a non-profit organisation funded by Bill and Melinda Gates Foundation and many other philanthropic organisations, is conducting field trials of Wolbachia-infected mosquitoes in India, Australia, Indonesia and Brazil.

In a recent international conference in US, the WMP had presented its studies on Wolbachia and Aedes aegypti mosquitoes. The Wolbachia trials in Australia, Indonesia and Brazil indicated a 76 per cent drop in dengue cases in Indonesia, while 75 per cent and even lower in Brazil. Surprisingly, in Queensland, Australia, there was a 96 per cent reduction of dengue infections due to Wolbachia.

India experience

India has been relatively a late entrant in realising the potential of Wolbachia in reducing vector-borne ailments. Recently, Indian Council of Medical Research (ICMR), World Mosquito Program (WMP) and ICMR-Vector Control Research Centre (VCRC) have taken up the project to conduct field trials of Wolbachia-infected Aedes aegypti in Puducherry.

In fact, this September, VCRC invited experts from across the world to participate in the project titled ‘Alternative strategy for dengue control in India’. As part of this trial, the ICMR researchers will release Aedes aegypti mosquito carrying Wolbachia in the field and conduct bio-safety studies. The study essentially will focus on identifying and assessing risks associated with the release of Aedes mosquitoes carrying Wolbachia into naturally occurring populations.

The ICMR and WMP laboratory studies on the impact of Wolbachia on dengue and chikungunya viruses were completed. In the coming months, researchers will introduce Wolbachia-infected mosquitoes in two regions of six lakh population in Puducherry and will rigorously evaluate the impact on the transmission of dengue and other ailments. The ICMR has also collaborated with Monash University of US to develop such mosquitoes.

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