UF Researcher Designs Pill To Control Mosquitoes

December 02, 1997

VERO BEACH---Dov Borovsky wants to put mosquitoes on a diet.

Under the Borovsky three-day diet plan, legions of anorexic little buzzers would just starve to death. And that's exactly the idea.

The University of Florida scientist says a mosquito "diet pill" he has perfected alters mosquito digestion, making it impossible for them to feed, lay eggs or survive.

As a mosquito control breakthrough, the diet pill could save lives.

"We hope this can stop the advance of malaria and other mosquito-borne diseases," said Borovsky, an insect biochemical and molecular biologist at the Florida Medical Entomology Laboratory, a part of UF's Institute of Food and Agricultural Sciences. "It works on all mosquitoes, all over the world."

In the mosquito control war, mosquitoes are winning. There are more than 3,000 species of mosquitoes. Worldwide, mosquito-borne diseases infect about 700 million people each year and kill 3 million, according to the Centers for Disease Control.

But the diet pill, which could be on the market within a year, is a promising new weapon, not only because it is wickedly efficient but because it also is safe for the environment.

And this diet plan is no secret. Borovsky is quite willing to share his recipe for mosquito death.

First, take 100,000 mosquito ovaries, dried and crushed into a powder that contains their digestive control hormone. From the nearest pool or pond, scrape off the green scum, also known as chlorella, an algae. Insert the hormone into the chlorella, make it into a pill, then place the pill into any water body where mosquitoes are known to breed. Then watch the larvae feast on the chlorella. Famine follows.

Borovsky said when he first pulled out mosquito ovaries, homogenized them and inserted them back into mosquitoes, he found that the mosquitoes produced no more eggs.

"So at first we thought we had a birth control pill," Borovsky said. "But then we found that the reason they were not producing eggs was because they were not digesting, so then we knew we had a diet pill, not a birth control pill.

"Fortunately, now we can synthesize the hormone, so we don't have to use 100,000 ovaries for each batch anymore," Borovsky said.

The synthesized hormone is inexpensive, as is chlorella, which is found and produced worldwide. Chlorella, in fact, turns out to be the perfect ride for the mosquito hormone, because it can be freeze-dried and stored for long periods and then brought back to life as the deadly diet pill.

The mosquito fen-phen is benign environmentally. Unlike DDT and some other pesticides, it does not alter the environment in any way, except for poisoning the larval lunch. Mosquitoes that feed on the hormone-laced chlorella starve to death within 72 hours.

"This is a natural bullet that we can use in the environment because the hormone doesn't stay in the environment," Borovsky said. "The chlorella stops producing the hormone within three weeks."

That's by design, Borovsky said. If the hormone were incorporated into the chlorella genome and chlorella continued to produce the hormone, making it omnipresent in the environment, mosquitoes could become resistant to it. But the hormone sits outside the genome, and after the third division of the chlorella it no longer can be detected.

Of course, Borovsky points out, if mosquitoes become resistant to their own reproductive hormone that could have unknown adverse consequences for them as well.

"We have to stay a step ahead of them or outsmart them all over again," Borovsky said.

In the decade since he began work on the pill, Borovsky has made believers out of even the most ardent doubters.

"Ten years ago, everybody was laughing at us, but now they are taking us seriously," Borovsky said. "Eight years ago, at a Vancouver meeting, a colleague harshly criticized this work. He just did not believe it."

The next step, Borovsky says, is to develop diet pills for infamous agricultural pests. Current methods to keep agricultural pests from molting fall short of protecting crops, Borovsky said.

"A pest that doesn't molt but still feeds is still a problem," Borovsky said. "By putting the diet pill into the crop or into the plant, the insect feeds and then dies before it takes its next meal."


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University of Florida

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