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Incompatible Insect Technique (IIT)
The Incompatible Insect Technique (IIT) uses Wolbachia, a naturally-occurring bacteria to help suppress mosquito populations. It is a safe, proven method of mosquito control.
This approach takes advantage of the fact that mosquitoes with different, incompatible strains of Wolbachia can’t produce viable offspring. Male mosquitoes with one strain of Wolbachia can only reproduce with females with a compatible strain of Wolbachia. Conversely, males with one strain of Wolbachia cannot produce viable offspring with females that have a different, incompatible strain of Wolbachia.
How It Works:
For this project, egg rafts of the southern house mosquito were collected from Hawaiʻi and sent to a facility on the U.S. continent. In a laboratory setting, researchers transferred an incompatible strain of Wolbachia into the mosquitoes, then reared large numbers of them. Once separated by sex, only male mosquitoes (which do not bite) are transported from the rearing facility and released back into mosquito breeding grounds in Hawaiʻi to mate with wild females. The development and production of incompatible males is done in a facility on the U.S. continent because Hawaiʻi doesn’t currently have a facility for producing large amounts of incompatible male mosquitoes
We can think of Wolbachia bacteria as tiny puzzle pieces inside mosquitoes. Males and females have to have matching puzzle pieces *(i.e. matching Wolbachia strains) to successfully reproduce.
The Wolbachia-incompatible male mosquitoes are released by helicopter over native forests where the endangered honeycreepers reside. They live for only a week but have an important task: to mate with wild females. Because of their incompatible Wolbachia strains, the females lay eggs that never hatch. With consecutive releases, mosquito populations decrease because no new generations are produced. Fewer mosquitoes is great for our birds! The decrease in mosquito populations means that there will be fewer mosquitoes that are able to transmit fatal avian malaria to our endangered honeycreepers.
"The mosquito control is so hopeful, because it feels like such a big, bold new thing, combating the problem we've know was there the whole time but didn't have the ability to fight it."
Christopher Warren
Forest Bird Program Coordinator
Haleakalā National Park
Wolbachia Facts:
Wolbachia is a naturally-occurring, intracellular, bacteria found in over half of all insect species worldwide.
It is already present in Hawai'i in numerous native and non-native insects.
Wolbachia cannot be transferred from the mosquito to humans, pets, or other animals like birds and bats - it can only survive in arthropod species.
Incompatible male mosquitoes (red) are released in such numbers that they overwhelm the wild males (blue) and so are more likely to mate with wild females.
Thousands of incompatible males are about to be dropped over native forest in Maui. The males come in completely bio-degradable cardboard tubes and are deployed over a grid.
Wolbachia (in green) within the ovaries of a mosquito.
Zhiyong Xi/ Michigan State University
Wolbachia: World Use
"Wolbachia IIT has been used for decades all over the world. We know that it's safe."
Dr. Christa Seidl
Mosquito Research & Control Coordinator. Maui Forest Bird Recovery Project
There are several different techniques using Wolbachia to control mosquito disease transmission. Some techniques look to suppress the overall population while others look to replace the current population with a mosquito that is less capable of transmitting disease.
Regardless of the end goal, Wolbachia has been successfully used around the globe to reduce mosquito populations that transmit deadly human diseases such as dengue and Zika. Countries where Wolbachia releases have been used to suppress dengue, for example, include: Australia, Brazil, Columbia, Indonesia and Vietnam.
In the continental United States, homeowners in Kentucky can now purchase regular releases of Wolbachia-incompatible mosquitoes to reduce the presence of Asian tiger mosquitoes (Aedes albopictus) around their homes.