How this bacterial strain from mosquito gut may help combat dengue                                                                 


Mosquito being reared at the molecular microbiology lab, Bharathiar University

One of the novel ways being experimented to control dengue and chikungunya is to release mosquitoes infected with a bacteria, Wolbachia, which prevents replication of disease-causing virus in the guts of mosquitoes. Now Indian scientists have found that a strain of wolbachia naturally occurs in mosquito species, Ae. Aegypti, in South India.

Wolbachia is shown to hinder the replication and dissemination of pathogens in mosquito besides, inducing reproductive abnormalities. Therefore, researchers have been artificially infecting mosquitoes with wolbachia and exploring if such mosquitoes may be released to for controlling dengue.

Though, the prevalence of wolbachia in Culex mosquito was detected in 1924, the wolbachia infection of Anopheles mosquitoes was detected only in 2014. Now scientists in Coimbatore have identified a new strain of wolbachia belonging to the supergroup B in Ae. Aegypti.

“We wanted to find out if Aegypti mosquitoes from Western Ghats that invade Coimbatore city harbour wolbachia either as a free-living entity or integrated with the mosquito genome. The rationale in targeting Aegypti mosquitoes from Western Ghats was that they breed in the wild and this probably widens the scope to tap their diversity,” explain researchers from Bharathiar University and Pondicherry University who conducted the study.

Mosquitoes being collected from field in Coimbatore

"Wolbachia is shown to hinder the replication and dissemination of pathogens in mosquito besides, inducing reproductive abnormalities. "

Certain strains of wolbachia have proven efficient to interfere with mosquitoes’ biology thereby reducing virus transmission. It is also safe to humans. That’s why scientists have been trying to transinfect this bacterium into mosquito eggs artificially and release them. Mostly, the bacteria get expelled from the mosquitoes in subsequent generations, unless the infection happens in a natural way. So finding the natural occurrence of wolbachia strains in these mosquitoes is important.

The researchers collected mosquitoes from various regions of Coimbatore. They confirmed the presence of wolbachia using specific 16S rRNA gene primers and Multi Locus Sequence Typing. The team also examined the bacterial spread in the mosquito’s body using Transmission Electron Microscopy. They found high bacterial density in reproductive tissues compared to other body tissues. This implies the possibility of natural infection in the subsequent generations.

“Wolbachia interrupts viral replication in mosquitoes. This results in low viral concentration within mosquitoes, making them incapable of transmitting the disease. We are now studying the mechanism of reproductive abnormalities in mosquitoes caused by this bacterium as well as the impact of wolbachia bacteria on replication of disease-causing viruses,” said Sivaraman Balaji, a member of the research team, while speaking to India Science Wire.

“Yet another dimension in the dynamics of control of Ae. aegypti mosquitoes is to look for variants in wolbachia genome exhibiting potential traits which hitherto have not yet been studied nor exploited. More studies need to be carried out to assess its importance and efficacy in controlling Ae. aegypti population,” researchers have observed.

The study results have been published in the journal FEMS Microbiology Letters. The research included S. Jayachandran (Pondicherry University); S. R. Prabagaran and Sivaraman Balaji (Bharathiar University).
India Science Wire

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