Thursday, August 31, 2017

The mosquito microbiome: An ally in the fight against disease

The annoying buzz of pesky little mosquitoes. At this time of year, the sound can be heard in backyards all around the world. Due to emerging threats like Zika and Dengue virus, people are becoming more and more familiar with the harm these little devils can cause. While vaccines and treatments for many mosquito-borne illnesses remain elusive, some researchers are placing new hope in other micro-organisms who may be able to play a role in preventing these dangerous diseases.

Previous work focused on malaria and its vector, the anopheline mosquitoes, has implicated micro-organisms, such as bacteria or fungi, within the mosquito to have an effect on the mosquito's ability to transmit the disease. Numerous studies in both Anopheles stephensi and Anopheles gambiae have shown that microbes in their midguts can influence the malarial parasite's ability to develop and transmit to new hosts. This is also not a new concept in the Aedes mosquitoes, the vectors for many of the mosquito-borne viruses. Wolbachia bacteria have been successfully introduced multiple times into these mosquitoes to prevent infection in the past.

Most previous studies have focused on introducing microbes to adult mosquitoes. In the field, this naturally presents challenges with application as adult mosquitoes are constantly migrating from place to place. However, recent work highlights that similar strategies could be used on mosquito larvae to influence their ability to transmit disease as adults. Larvae are much more targetable, due to the relative ease of identifying larval development sites.

In the latest study of the mosquito microbiota and its effects on vectorial capacity (the ability of a vector, like the mosquito, to transmit a particular disease), researchers found that differences in bacterial colonization of larvae could have an effect on the adult mosquito's traits. This means that by changing the bacteria larvae are exposed to, you could influence their ability to transmit disease as adults.

While there are many environmental concerns that will need to be addressed before a strategy altering the bacterial make-up of mosquito breeding sites, this new study and the growing body of work focusing on the mosquito microbiome's effects on vectorial capacity offer hope for new strategies to control disease spread. Perhaps some day we will be able to add a simple pellet of bacteria to a pool of water with mosquito larvae and prevent all the subsequent adults from transmitting disease. This may seem like a far-fetched dream today, but with continued research, it could one day be a reality.

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