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Mosquito birth control and other ways to fight Zika virus

The Zika virus is transmitted by mosquitoes. Many cases in the U.S. are travel-related infections, involving people infected in other countries with Zika-carrying mosquitoes. But now, some U.S. cases involve local mosquitoes infecting people in nontravel incidents. As officials deal with nontravel Zika virus cases in Miami, the Food and Drug Administration has approved the use of genetically modified mosquitoes to eradicate those that carry the virus. Here are three methods of mosquito control being used to fight Zika.

Travel-related Zika cases by state

Totals as of Aug. 17

Genetically modified mosquitoes

This approach uses molecular biology as birth control for mosquitoes. Called the RIDL technique, for "release of insects with dominant lethality," it's an update to a similar pest-control technique. It is being field-tested in Brazil, the Cayman Islands, Malaysia and possibly the Florida Keys this fall.

1. Millions of mosquitoes are reared or collected and the eggs are sent to a lab. A lethal gene is microscopically inserted into the mosquito embryos that kills or disables adult females, the ones that draw blood and spread disease.

2. Once born, the males are released to mate with wild females and transfer the lethal gene.

3. The female lays eggs. When they hatch, only the male larvae develop and females die. The male offspring grow and pass the copied lethal gene to more wild female mosquitoes.


Radiation-treated mosquitoes

This technique has been used against disease-carrying insects since the 1950s.

1. Millions of male mosquitoes are reared or collected and irradiated in a lab to make them sterile.

2. The sterile mosquitoes are released into the wild over a wide area.

3. The sterile mosquitoes mate with females.

4. The females lay eggs but they are not viable or don’t hatch.


A plane sprays pesticide over the Wynwood neighborhood in Miami (Joe Raedle / Getty Images).

Pesticides

Mosquito control districts use airplanes to spray pesticides on areas where mosquitoes breed in communities affected by outbreaks. There are different pesticies for adult mosquitoes (adulticides kill adult pests immediately) and for larvae (larvicides kill young mosquitoes in a few days). Insecticides can also be applied by hand with a sprayer or fogger or by truck. A downside is mosquitoes can become resistent to pesticides over time.

Sources: OXITEC, International Atomic Energy Agency, U.S. Centers for Disease Control and Prevention

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