Suppression or replacement?
There are two major strategies in field trials today that use Wolbachia to reduce the transmission of mosquito-borne diseases.
Suppression strategy: This approach, which NEA is now piloting under Project Wolbachia – Singapore, aims to reduce mosquito-borne disease transmission by suppressing mosquito populations. It involves the release of non-biting male Wolbachia-carrying mosquitoes to mate with urban female mosquitoes. As these matings produce eggs that do not hatch, continued releases result in reduced mosquito populations. Besides Singapore, this approach is also being piloted by disease control programmes in Australia, China, Thailand, and the US, among other countries. Click here to read more about how this approach works.
Replacement strategy: This approach aims to replace field mosquito populations with Wolbachia-carrying mosquitoes, which have a reduced ability to transmit diseases such as dengue. It involves the release of both non-biting male and biting female Wolbachia-carrying mosquitoes, which then introduce Wolbachia into field mosquito populations. This approach is being piloted by disease control programmes in Australia, Brazil, Indonesia, Malaysia, and Vietnam, among other countries.
Why is the Wolbachia suppression strategy most suitable for Singapore?
After extensive laboratory studies, literature reviews, and consultation with experts, NEA determined that the
Wolbachia suppression strategy was most suitable for Singapore’s context. Here are some of the most important factors we considered:
| | Strategy |
| Considerations | Replacement | Suppression
(NEA’s chosen approach) |
| Biological | Our lab studies found that when introduced into local Aedes aegypti mosquitoes, Wolbachia only partially blocks dengue transmission. This may make the replacement approach less effective in Singapore’s context. A rise in mosquito population could theoretically negate the partial block, or even result in an increase in dengue transmission. | Suppression approach targets the mosquito population itself, and does not rely on Wolbachia’s ability to block disease transmission. |
| Social acceptance | After decades of good vector control in Singapore, the release of female mosquitoes (required by the replacement approach) will increase biting pressure. | Suppression approach involves the release of only male mosquitoes, which do not bite or transmit disease. |
| Public
education | The release of female mosquitoes in the replacement approach is at odds with Singapore’s long-standing focus on prevention of mosquito breeding, and may send mixed signals to the public. | Suppression approach is consistent with Singapore’s decades of public messaging on staying vigilant against mosquito breeding. |
| Ecological | The replacement of field mosquito populations with Wolbachia-carrying insects may be permanent. It has been shown to successfully impede dengue transmission. However, subsequent suppression of Wolbachia-Aedes population cannot rely on the same Wolbachia-Aedes, and will require more time and alternative measure.
| Release of male Wolbachia-Aedes can be halted at any time and leaves no ecological footprint. Replacement with Wolbachia-Aedes can follow suppression if needed. |