Can Bacteria-Infected Mosquitoes Stop the Spread Of Zika?

Experts in infectious disease believe that one of the least appreciated organisms on earth is wolbachia. This particular organism infects millions of invertebrates including shrimps, spiders and even parasitic worms as well as nearly 2/3rd of insects. Once inside the invertebrate, the wolbachia takes over the host’s reproductive system and also greedily prevents them from acquiring other very common infections.

Ever since the outbreak of the Zika virus in South America in 2015, researchers have been suspecting that the wolbachia may be protecting the mosquitoes from the Zika virus. New research now reveals that perhaps releasing the wolbachia infected mosquitoes into the wild may help curb this Zika virus epidemic.

So far, no vaccine is available and the Zika virus has already reached the North American continent. Unlike other infections, the Zika virus is known to affect the fetus during pregnancy causing severe deformations of the skull and face.

The wolbachia was initially discovered nearly 90 years ago when researchers in Boston found the organism in some mosquitoes. At that time, no significance was attributed to this finding. What they discovered was that instead of just circulating in the blood, the wolbachia started to reside in individual cells. Hence when the mosquito bites, the wolbachia cannot be easily transferred to another host. All infected mosquitoes carry wolbachia in their eggs and the offspring are also born infected. Over the few decades, the wolbachia has evolved into many other strains using a range of tricks to increase its numbers inside invertebrates. In almost all cases, the number of infected female hosts appear to have increased.

Some of the wolbachia strains make it nearly impossible for an infected male to reproduce offspring with an uninfected female. The eggs in most cases fail to mature. It is this cytoplasmic incompatibility that gives the wolbachia-infected females a key advantage in the reproduction rate, since they are able to mate successfully with uninfected and infected males.

In one study from Australia, it was observed that when the wolbachia found residence in mosquitoes, it now completely blocked the dengue virus from infecting other hosts. At present nearly 390 million individuals are infected with the dengue virus each year and the assumption is that if the mosquitoes carrying the infection are protected from it, then they will not be able to transmit the virus to humans.

Currently this theory is being tested out in the field. In 2011 hundreds of thousands of wolbachia carrying mosquitoes were released in northern Australia and quickly established themselves in the wild. Today, the majority of the mosquitoes, including Aedes aegypti, the strain that transits the Zika virus, have also been found to carry wolbachia.