What is Wolbachia
Wolbachia is a safe, naturally occurring bacterium found in more than 60% of insect species, including butterflies, bees, dragonflies and some species of mosquitoes such as Aedes albopictus and Culex quinquefasciatus. Organisms in the natural environment have been continuously exposed to Wolbachia for millions of years. Wolbachia CANNOT survive in the environment outside insect hosts
Wolbachia DOES NOT harm humans or animals
- Humans and animals have always been exposed to Wolbachia. This happens when they come into contact with insects, eat insects, or eat foods such as fruit that are exposed to insects.
- Despite this, there are no reports of Wolbachia causing harm to humans or animals.
Wolbachia CANNOT be transferred through a mosquito bite
- Humans and animals are constantly exposed to the bites of female mosquitoes that naturally carry Wolbachia, but there are no reports of Wolbachia transmission via bites.
- A study found that human volunteers exposed to bites from female Wolbachia-carrying Aedes aegypti (Wolbachia-Aedes) mosquitoes showed no immune response to Wolbachia.
Wolbachia CANNOT survive outside insects
- Wolbachia can only survive inside insect cells. Wolbachia cannot survive in the outside environment.
- When the host insect dies and decomposes, Wolbachia decomposes naturally together with the insect’s body.
Wolbachia DOES NOT survive after being ingested
- There are no reports of mosquito predators (such as fish, lizards, and frogs) becoming infected with Wolbachia.
- A study found that spiders fed on Wolbachia-carrying mosquitoes did not acquire Wolbachia.
Is it safe to release male Wolbachia-Aedes mosquitoes?
NEA’s comprehensive risk assessment (see detailed reports below) of Wolbachia-Aedes suppression technology has determined it to be safe, with no risk to human health and insignificant risk to ecology. This conclusion is consistent with findings from other groups around the world.
The risks associated with releases of male Wolbachia-Aedes mosquitoes are low or negligible:
- Low risk of community becoming less vigilant with source reduction. Wolbachia-Aedes suppression technology is not a silver bullet, and is intended to complement, not replace, source reduction efforts. Continued community source reduction efforts are critical for the success of the technology.
- Negligible risk from temporary increase in male mosquito numbers following a release, as male mosquitoes do not bite or transmit disease.
- Negligible risk from unintentional release of female Wolbachia-Aedes mosquitoes. Unintentional release of large numbers of female Wolbachia-Aedes is avoided with laboratory security and robust sex-sorting processes achieved through technologies developed with NEA’s partner, Orinno Technology Pte. Ltd. NEA is also collaborating with Verily Life Sciences LLC to use artificial intelligence to separate the male from the female mosquitoes with very high accuracy. To find out more about Verily’s sorting technology, please click here. However, as sex-sorting is not 100% accurate, a very small number of female Wolbachia-Aedes mosquitoes can still be released. This number is too small to have any noticeable impact on biting, and the ability of the females to transmit disease would largely be blocked by Wolbachia. NEA also takes the additional step of exposing sorted pupae to low-dose X-ray irradiation to sterilise any remaining females. This prevents Wolbachia from establishing itself in the mosquito population, as the small number of females released will not be able to reproduce. Prevention of establishment is important for the continued effectiveness of Wolbachia-Aedes suppression technology, which relies on incompatible matings between Wolbachia-carrying males and wildtype non-Wolbachia-carrying females.
- Negligible or low risk of niche replacement by Aedes albopictus, the secondary vector of dengue in Singapore. Aedes albopictus prefers greenery, while Aedes aegypti prefers urban spaces. NEA’s vector population surveillance data indicates a low risk of niche replacement if the community continues to carry out source reduction.
- Negligible risk of endangering other species in the ecosystem. Mosquitoes typically make up a very small percentage of the diet of predators such as frogs, lizards, or spiders, and there are no predator species that depend solely on Aedes aegypti as a food source.
Risk assessment reports
To assess the safety of Wolbachia-Aedes suppression technology, NEA conducted critical reviews of existing knowledge and research, and consulted international and local experts and stakeholders, including researchers, medical and healthcare professionals, and non-governmental organisations. Detailed risk assessment reports can be found at the links below:
NEA's publication on 'How Safe is Wolbachia for AedesControl? A risk assessment for the use of male Wolbachia-carrying Aedes aegyptifor suppression of the Aedes aegypti mosquito population’
Risk assessment for the use of male Wolbachia-carrying Aedes aegypti for suppression of the Aedes aegypti mosquito population
Impact assessment on the release of X-ray or similar treated Wolbachia-Aedes mosquitoes for the urban Aedes aegypti mosquito population
NEA also commissioned an independent risk assessment, which similarly concluded that Wolbachia-Aedes suppression technology is safe: