01. What is Wolbachia?
Wolbachia are safe, natural bacteria present in up to 60% of insect species, including some mosquitoes. However, Wolbachia is not usually found in the Aedes aegypti mosquito, the primary species responsible for transmitting viruses such as Zika, dengue, chikungunya and yellow fever.
For many years, scientists have been studying Wolbachia, looking for ways to use it to potentially control the mosquitoes that transmit human diseases. The World Mosquito Program’s research has shown that when introduced into the Aedes aegypti mosquito, Wolbachia can help to reduce transmission of theZika, dengue, chikungunya and yellow fever viruses to people.
You can read our Wolbachia factsheet here.
02. How does Wolbachia work?
Wolbachia works in two ways within a mosquito. The first way is to boost the natural immune system of the mosquito to make it harder for the mosquito to support the Zika, dengue, chikungunya or yellow fever infection. If the mosquito can’t get infected, then it can’t transmit these viruses to people.
The second way Wolbachia works is by competing against viruses for key molecules like cholesterol. Both the viruses and Wolbachia need cholesterol to survive inside the mosquito. When Wolbachia is present, it consumes these molecules and makes it harder for the viruses to grow. If it’s harder for the viruses to grow, then it’s harder for them to be transmitted.
Learn more about how Wolbachia works here.
03. How does the World Mosquito Program use Wolbachia?
The WMP introduces Wolbachia into male and female Aedes aegypti mosquitoes in the laboratory and releases them into the wild. Aedes aegypti mosquitoes are the primary vector that transmit the Zika, dengue, chikungunya and yellow fever viruses.
Once Wolbachia carrying mosquitoes are released, they breed with wild mosquitoes. Over time, the majority of mosquitoes carry Wolbachia. These mosquitoes have a reduced ability to transmit viruses to people, decreasing the risk of Zika, dengue, chikungunya and yellow fever outbreaks.
Our Wolbachia method can protect communities from mosquito-borne diseases without posing risk to natural ecosystems. Unlike most other initiatives, our method is natural and self-sustaining.
04. Is Wolbachia safe?
Wolbachia is safe for humans, animals and the environment. The WMP’s Wolbachia method helps to protect communities from mosquito-borne diseases like Zika, dengue, chikungunya and yellow fever and does so without risk to natural ecosystems or human health.
Following years of laboratory and field-based research, the WMP’s findings have been subjected to rigorous independent assessments. The results concluded that there is negligible risk associated with the release of Wolbachia carrying mosquitoes and that Wolbachia is safe for people, animals and the environment.
05. Will the bite of a mosquito with Wolbachia hurt more than a normal bite?
No, people who are bitten by an Aedes aegypti mosquito containing Wolbachia will not notice any difference or be harmed in any way.
06. Is Wolbachia harmful to the environment?
No, Wolbachia are naturally occurring bacteria that are safe for humans, animals and the environment.
For more information, read the CSIRO's Risk Assessment Report.
07. Do other animals carry Wolbachia?
Wolbachia is common among arthropods (including insects, spiders and other small animals with no backbone). Up to 60% of insect species naturally carry Wolbachia, including butterflies, dragonflies, moths and some mosquito species, but not the primary species of mosquito involved in the transmission of Zika, dengue, chikungunya and yellow fever.
Wolbachia is also found in certain types of roundworms – known as nematodes – but this is very different to the insect Wolbachia that we work with. Wolbachia is not found in any larger animals such as mammals, reptiles, birds and fish.
08. What type of Wolbachia does the World Mosquito Program work with?
Wolbachia refers to a whole genus of bacteria, of which there are many different types and strains. We’ve examined several strains of insect Wolbachia, and the most effective strain we’ve found is the one that we are currently using in the field - wMel.
Lately, our researchers have been examining new strains of Wolbachia, wMelCS, wRi and wPip, with exciting results. While we have had great success in establishing our current Wolbachia strain, wMel, in wild mosquito populations, testing additional strains could improve the impact of our work and provide a strategy to account for the possible evolution of resistant viruses.
As outlined in our new report, a new strain wMelCS warrants further investigation for potential release in our future field trials. You can read more about this latest research here.
09. How is Wolbachia transferred between mosquitoes?
Wolbachia can only be transmitted from parent to offspring inside the female’s egg. When a male mosquito that carries Wolbachia mates with a female without the bacteria then that female’s eggs don’t hatch.
Wolbachia infected female mosquitoes do not suffer from this effect and produce normal numbers of offspring – which carry Wolbachia. Initially, this reproductive effect will be very small as there will be few Wolbachia carrying mosquitoes in the population, but over successive generations the numbers of males and female mosquitoes with Wolbachia will increase.
This process is called cytoplasmic incompatibility (CI) and is important for Wolbachia propagation in mosquitoes.
Please refer to our short 3-minute animated video on CI for more information.
10. Is Wolbachia directly affected by the temperature in the environment?
Wolbachia and mosquitoes can both be affected by high temperatures. At high temperatures, the density of Wolbachia decreases in the mosquito (larvae and adults) and maternal transmission of Wolbachia is reduced. Importantly however, the evidence of successful Wolbachia establishment in Indonesia, northern Australia, Brazil and Colombia indicates that temperature is not typically a problem for establishing Wolbachia.