In battle against spread of chikungunya and dengue, ICMR finds unlikely ally — bacteria

NEW DELHI : To control the spread of dengue and chikungunya, scientists at the Indian Council of Medical Research have turned to an unlikely new ally — bacteria.

In a project under process over the last year, ICMR researchers have developed a strain of the Aedes aegypti mosquito — the main vector that transmits the viruses that cause dengue — into which Wolbachia, a naturally occurring bacteria, is introduced.

Wolbachia “inhibits” viral infection, which means, “people will feel the mosquito bite but they will not be infected. The bacteria will not allow the virus to replicate in the mosquito and so, the virus won’t be transmitted through a bite,” according to Dr Manju Rahi, Scientist-E, ICMR.

The mosquito variant has been named the Puducherry strain since it was developed at the Vector Control Research Centre (VCRC), Puducherry in collaboration with Monash University in Australia.

The mosquitoes are being reared in the laboratory and will be released into the open during field trials by the end of October.
ICMR Director-General Dr Balram Bhargava “The strain in Puducherry is ready and we will begin the field trials in the next few months. This strain will specifically help in reducing the number of dengue cases across the country.”

Dengue is transmitted by several species of mosquito within the genus Aedes. Symptoms include fever, headache, muscle and joint pains, and a characteristic skin rash that is similar to measles. There are four strains and Type-II and IV are considered more severe and normally require hospitalisation.

“The eggs of a mosquito carrying Wolbachia bacteria were brought to VCRC in India. They hatched and then mated with Indian mosquitoes. The process is called backcrossing and it has been done 12 times. From the process, we have derived the Puducherry strain and now the mosquitoes are being reared at the laboratory in VCRC. Few approvals are pending and after that, the mosquitoes will be released for field trials,” said Dr Rahi.

“This is a population replacement strategy. With the introduction of the new strain, there will be a gradual decline in the number of dengue cases. The mosquitoes in India will be replaced with those carrying Wolbachia bacteria.” According to Health Ministry data, in reply to a question in Lok Sabha, the country has reported 6,210 cases and six deaths from dengue until June 9 this year.

In 2017, India inked a partnership with Monash University to conduct laboratory trials on a global vector-control method. The university had come up with this method a few years ago and trials were conducted in Cairns in Australia, and the results were promising.

As a part of the Memorandum of Understanding (MoU), an Aedes aegypti strain carrying Wolbachia bacteria was imported to India from Monash University