Innovative Mosquito Reduction

The image discusses reducing invasive Aedes mosquitoes, highlighting that male Aedes aegypti do not bite and feed on nectar.

Sterile Insect Technique (SIT) and Incompatible Insect Technique (IIT)

These techniques have successfully reduced invasive Aedes aegypti populations in the Unites States and other countries and have been incorporated into Integrated Vector Management (IVM) programs to support evidence-based, environmentally responsible mosquito control. 

The methods used in California involve male mosquitoes. Male mosquitoes do not bite and they do not spread diseases.

What methods/techniques are being used to reduce Aedes aegypti mosquitoes in California and abroad?

Overall, there are two techniques:

1. Sterile Insect Technique (SIT)

SIT was first developed in the United States and has been used by government agencies to control insect pests, such as screwworms, invasive Mediterranean fruit flies, and other agricultural pests since the 1950s. Now, it is being used to control Aedes aegypti mosquitoes in California, Florida, and internationally. 

SIT involves the sterilization of non-biting male mosquitoes. When these males mate with female mosquitoes in the environment, all eggs produced by the female do NOT hatch. 

SIT Success Stories 

Current SIT programs for agricultural pests in the United States

  1. New World Screwworm in the United States
  2. Mediterranean fruit fly

IIT is currently used by mosquito and vector control agencies in California, Florida, and other countries and has successfully reduced Aedes aegypti mosquitoes. 

2. Incompatible Insect Technique (IIT)

This technique slightly differs from SIT because it uses Wolbachia, a common bacteria found in approximately 60% of insects, such as butterflies, bees, and dragonflies. It is added to male invasive Aedes mosquitoes, such as Aedes aegypti.  Once the Wolbachia male mosquito mates with female mosquitoes of the same species, all eggs that are laid do NOT hatch because of the Wolbachia. 

IIT Success Stories 

Current IIT programs in the United States and other Countries

  1. Hawaii - Wolbachia male mosquitoes have been released in Hawaii to reduce mosquito populations that transmit avian malaria and help protect endangered Hawaiian honeycreepers.
  2. Singapore - Successful suppression of dengue (a disease transmitted by the Aedes aegypti mosquito) in Singapore after Wolbachia male releases.

IIT is currently used by mosquito and vector control agencies in the United States and other countries and has successfully reduced Aedes aegypti mosquitoes. 

**NOTE: Both techniques of male mosquito releases are often grouped together as Sterile Insect Techniques (SIT) because they result in eggs that do not hatch. They are eco-friendly, safe, and effective, and they share the same goal: reducing invasive Aedes mosquito populations.

using three (3) main methods:

Wolbachia (technique: IIT) 

How does this Incompatible Insect Technique (IIT) method work?

  1.  Non-biting male mosquitoes with Wolbachia are released within a specified area.
  2. The released Wolbachia male mosquitoes mate with the female mosquitoes of the same species present in the area.
  3. After mating and taking a blood meal, the female mosquitoes lay eggs that do NOT hatch.

Learn more about the method:

 

Irradiation/X-ray (technique: SIT) 

How does this Sterile Insect Technique (SIT) method work?

  1.  Non-biting male mosquitoes are exposed to a low dose of X-rays, which sterilizes them.
  2. The sterilized males are released into a specified area, where they mate with wild female mosquitoes of the same species.
  3. The female mosquitoes lay eggs after taking a blood meal, but the eggs do not hatch. Over time, this reduces the mosquito population, resulting in fewer female mosquitoes, fewer mosquito bites, and a lower risk of mosquito-borne disease.

Learn more about the method:

 

Self-limiting mosquitoes 

How does this method work?

  1. Non-biting male mosquitoes carrying a self-limiting trait are released within a specified area.
  2. The released male mosquitoes mate with wild female mosquitoes of the same species.
  3. After mating and taking a blood meal, the female mosquitoes lay eggs. These offspring inherit the self-limiting trait and do not survive to adulthood. Over time, this reduces the mosquito population, resulting in fewer female mosquitoes, fewer mosquito bites, and a lower risk of mosquito-borne disease.

Learn more about the method:

 

The image depicts three methods of Sterile Insect Techniques: Wolbachia, Irradiation, and Self-limiting mosquitoes.

Why is SIT/IIT being used for reducing Aedes aegypti mosquitoes?

Invasive Aedes mosquitoes, such as Aedes aegypti, are very difficult to control once they are established in an area. 

Here are some of the reasons why invasive Aedes mosquitoes, like Aedes aegypti, are difficult to control:

  1. These mosquitoes, also referred to as "ankle biters", have evolved to thrive in populated areas. They prefer to bite humans and lay eggs in small, hidden water sources, sometimes as small as a bottle cap. 
  2. They also lay eggs that can survive 6+ months outside of water on the sides of containers and plants in and around homes (different from local/native species). This mosquito is often transported to new areas in the egg stage.
  3. Additionally, several invasive Aedes populations have developed resistance to pesticides used for adult mosquito control.

By using an environmentally safe tool from our Integrated Vector Management (IVM) toolbox, the District aims to decrease the number of Aedes aegypti mosquitoes in the area. Fewer mosquitoes mean fewer biting females, reduced nuisance and public health impacts, and a lower risk of transmission of mosquito-borne diseases, such as dengue, chikungunya, and Zika. 

Why is SIT/IIT effective for reducing Aedes aegypti mosquitoes?

        1. Only female mosquitoes bite; they need a blood meal to produce eggs. 

Mosquito-borne diseases are spread through mosquito bites. Male mosquitoes do not bite and do not spread diseases. This means residents in the area will not experience more bites from the released male mosquitoes. 

         2. Female mosquitoes only mate ONCE.

Once a released male mosquito mates with a female mosquito, that female mosquito produces eggs (after a blood meal) that will never hatch.  

         3. Mosquitoes can only mate within the same species.

This ensures that releases of one mosquito species pose no risk to people, animals, pets, or the environment. Local mosquitoes in the environment are unaffected.

Leveraging and using Innovative Mosquito Reduction Techniques

SIT/IIT are one component in our Integrated Vector Management toolbox. The Alameda County Mosquito Abatement District remains committed to using environmentally sensitive and effective approaches to mosquito control for all communities and the environment in Alameda County. 

Integrated Vector Management Program Toolbox

Learn more about Innovative Mosquito Reduction