Mosquitoes Given Shots to Block Spread of Dengue Fever

Using tiny needles finer than a human hair, researchers have been able to inject into mosquitoes an altered virus that keeps the flying pests from infecting people with dengue fever, a study said Friday.

Experts said the work opens up a possible new avenue for controlling diseases, such as malaria, that are carried by mosquitoes.

Inoculating individual bugs may not be practical, said Ken Olson, a researcher at Colorado State University in Fort Collins, but the study has shown “it is feasible to molecularly alter a mosquito so that the dengue virus cannot reproduce.”

Dengue fever is spread when a mosquito takes blood from a human who has the disease.

The virus reproduces in the mosquito salivary glands and is then injected into a new victim when the mosquito attacks another human.

The disease can be lethal, causing severe fever, bleeding and shock.

Olson, lead author of the study, said the researchers altered another virus, called Sinbis, so that it made a protein that blocked the replication of dengue viruses.

The researchers then injected the Sinbis virus into the abdomen of mosquitoes that can carry the dengue fever virus. Some of the mosquitoes also were injected with the dengue virus.

Eleven days later, Olson said, the saliva and the salivary glands of the mosquitoes were analyzed for the presence of dengue virus.

Among the mosquitoes injected with the altered Sinbis virus “there was no dengue virus,” he said. “The dengue did not replicate.”

Dr. Louis H. Miller, a tropical disease expert at the National Institutes of Health, said the work is important because it explores methods of controlling the mosquito without insecticides.

How do you get a mosquito to sit still for an injection?

“If you put them on ice, they go to sleep,” explained Olson. He said the researchers put batches of the mosquitoes in refrigeration and then worked with them on a chilled table that kept the insects unconscious.

While the mosquitoes were asleep, the researchers used the minute needles to inject one microliter of the altered virus into their abdomens.

Olson said one microliter is such a small bit of liquid that it might not cover the period at the end of a sentence.