The St. Croix
Mosquito Project

The Virgin Islands Department of Health (VIDOH) Vector Control Program and their partners, Verily and MosquitoMate, are beginning a project to evaluate if the Wolbachia-based Sterile Insect Technique will reduce Aedes aegypti mosquitoes on St. Croix like it has in other places around the world.

Dengue, Zika and the other mosquito borne diseases regularly impact the Virgin Islands. Unfortunately we don’t have effective tools to fight these mosquitoes and prevent outbreaks. This is why the USVI Department of Health, with the support of the Centers for Disease Control is planning to evaluate the effectiveness of the mosquito Sterile Insect Technique in the USVI. By releasing non-biting male mosquitoes, which aren’t genetically modified, we hope to reduce the number of dangerous Aedes aegypti mosquitoes.

What to know
What is the St. Croix Mosquito Project?

The St. Croix Mosquito Project is an evaluation of the Sterile Insect Technique (SIT) to reduce the amount of Aedes aegypti mosquitoes in some neighborhoods on St. Croix. Following public engagement, our partnership, led by the Virgin Islands Department of Health (VIDOH), may release non-biting, sterile male Aedes aegypti mosquitoes into some neighborhoods on St. Croix. The goal is to learn how effectively it will reduce this mosquito in our local environment. Similar programs have been used around the world with positive results.

This project uses a Wolbachia-based SIT, and does not use genetic modification (GM). Wolbachia is a naturally occurring bacterium. The VIDOH is leading the project in partnership with Verily and MosquitoMate. Funding for this project is provided by The Centers for Disease Control and Prevention (CDC) and administered by National Association of County and City Health Officials (NACCHO).

So what’s next? VIDOH and partners are already working with residents to trap mosquitoes across the island to understand where Aedes aegypti are in St. Croix. We’ve also begun outreach to inform residents about how they can protect themselves from these mosquitoes and how a sterile male release program could work in St. Croix. To find out how you can help, please contact the Outreach Coordinator for the VIDOH Vector Control Program and the St. Croix Mosquito Project at 340-690-9177 or send an email to dohvectorcontrol@usvi.onmicrosoft.com. You can also look at us for local community events including the Agricultural Fair and Wellness Wednesdays.

How is the St. Croix Mosquito Project using Sterile Insect Technique (SIT) with mosquitoes?

The project will involve releasing non-biting, sterile male Aedes aegypti mosquitoes with Wolbachia, a naturally-occurring bacterium that is found in most insects worldwide, but not in Aedes aegypti mosquitoes.

When non-biting, sterile male Aedes aegypti mosquitoes with Wolbachia are released into neighborhoods and mate with wild Aedes aegypti females without Wolbachia, the female mosquitoes’ eggs do not hatch, producing no offspring. Over time, this reduces the amount of Aedes aegypti mosquitoes in areas where non-biting, sterile male Aedes aegypti mosquitoes are released. These mosquitoes are not genetically modified (GM).

FAQ | St. Croix Mosquito Project

The Sterile Insect Technique (SIT) is a method of insect control where sterile insects are released to mate with the wild insects of the same species. Together, the released sterile insects and wild insects cannot reproduce and over time, this reduces the amount of that one insect species only. SIT has been used since the 1950s to successfully control many insects, including agricultural pests. Unlike some pesticides that can impact many different types of insects, SIT is species-specific. The St. Croix Mosquito Project is using a Wolbachia-based SIT to target Aedes aegypti mosquitoes, which can spread dengue, Zika, and chikungunya, and does not involve genetic modification.

Wolbachia is a naturally occurring bacterium that is found inside the cells of many different kinds of insects, including bees, butterflies, dragonflies and many types of mosquitoes, but not Aedes aegypti mosquitoes.

Yes, there are different types of SIT, depending on the species of insect and other reasons. The type of SIT that our project will use involves releasing non-biting male Aedes aegypti mosquitoes that have Wolbachia, a naturally occurring bacterium, in areas where biting female Aedes aegypti mosquitoes do not have Wolbachia. When the non-biting, male Aedes aegypti mosquitoes with Wolbachia mate with the wild biting female Aedes aegypti mosquitoes without Wolbachia, the female mosquitoes’ eggs don’t hatch, reducing their numbers over time. This Wolbachia-based type of SIT does not use radiation or genetic modification.

If a female insect without Wolbachia mates with a male insect of the same species that has Wolbachia, her eggs will not hatch, reducing their numbers over time.

Aedes aegypti mosquitoes do not naturally have Wolbachia. We release non-biting, sterile male Aedes aegypti mosquitoes with Wolbachia who mate with female Aedes aegypti mosquitoes. None of the eggs from those female Aedes aegypti mosquitoes can hatch.

Over time, the number of Aedes aegypti mosquitoes will go down in the area where the non-biting, sterile male Aedes aegypti mosquitoes with Wolbachia are being released.

Wolbachia is a bacterium that naturally lives in most insects and is not found in humans. It cannot be given to people or animals through an insect bite or contact with an insect. Wolbachia is very common: it is in more than half of insect species (bees, butterflies, and some mosquitoes, etc.) all over the world.

Our proposed project targets only one type of mosquito, Aedes aegypti. The Aedes aegypti mosquito is an invasive species that is not native to the territory or the Caribbean. There are many other mosquito types on St. Croix that support the food chain.

No. Continue to wear mosquito repellent, remove standing water around your yard and home, keep screens on your windows and doors, and fix broken screens. The Sterile Insect Technique (SIT) on St. Croix only targets a single type of mosquito, the Aedes aegypti mosquito that can spread dengue, Zika, and chikungunya, and there are still many other types of mosquitoes on St. Croix that could bite you.

We only release male Aedes aegypti mosquitoes because male mosquitoes cannot bite and cannot spread diseases to humans. Also, male mosquitoes find female mosquitoes to mate with, so they can be used successfully for the Sterile Insect Technique (SIT).

If you live in an area where non-biting, sterile male Aedes aegypti mosquitoes with Wolbachia are released, you may notice an increase in the non-biting male Aedes aegypti mosquitoes. Male Aedes aegypti mosquitoes are attracted to people to find female Aedes aegypti mosquitoes to mate with, but they cannot bite you.

We plan to release non-biting, sterile male Aedes aegypti mosquitoes with Wolbachia only in some areas of St. Croix, and we are determining those areas now. Communities outside of these areas will not have releases of non-biting, sterile male Aedes aegypti mosquitoes with Wolbachia.

There are many types of mosquitoes on St. Croix, and the St. Croix Mosquito Project only targets the Aedes aegypti mosquito. All other types of mosquitoes will be unaffected and may still bite. You should continue to protect yourself and your family to prevent mosquito bites from other types of mosquitoes by wearing repellent, removing standing water from your property and wearing long sleeves and long pants.

The Aedes aegypti mosquito can be hard to control using traditional control methods, like removing mosquito breeding sites and chemical pesticides. Our partnership is proposing SIT because it has been shown that it can reduce Aedes aegypti mosquitoes in other places, and we believe that it will work in the USVI. It can be another way to fight against Aedes aegypti mosquitoes that can spread dengue, Zika, and chikungunya.

Everyone can help control mosquitoes by removing or covering standing water in their yards, homes and businesses. Aedes aegypti mosquitoes like to lay their eggs in containers with water such as flower pots, old tires, outside toys, pet water bowls, etc.

Our partnership is monitoring Aedes aegypti mosquito numbers with mosquito traps around the island; if you see a trap, please do not disturb it.

If you’d like to get involved directly, please contact the Outreach Coordinator for the VIDOH Vector Control Program and the St. Croix Mosquito Project at 340-690-9177 or send an email to dohvectorcontrol@usvi.onmicrosoft.com.

About the team
The people behind the project

The St. Croix Mosquito Project is a VIDOH-led collaboration that brings together scientists, public health experts and community engagement specialists

Brett Ellis, PhD, MSPH Director, Territorial Public Health Laboratories, VIDOH
Krystal Seger, MSPH Entomologist, VIDOH
Lashonette Schjang, BA Public Health Educator, VIDOH
Field Team

If you see our field team, please say hello! If you have given permission to keep a mosquito monitoring trap on your property, our technicians will be checking in on them regularly. Once releases start, you will also see our drivers, who will be releasing sterile, non-biting male Aedes aegypti mosquitoes from our vans.