To preventatively combat mosquitoes that carry viruses, such as those that carry dengue fever or chikungunya, the various mosquito release techniques have so far shown varying degrees of effectiveness, ANSES said on Thursday, also calling for monitoring of possible unwanted effects.
In the quest for alternatives to insecticides, releases have been tested since the 2000s to combat Aedes mosquitoes, including the tiger mosquito, by reducing their populations or reducing their ability to transmit certain viruses.
The sterile insect technique involves releasing males that have been rendered sterile by irradiation. When they mate with wild females, the latter lay non-viable eggs.
With the incompatible insect, males are contaminated by a bacterium (Wolbachia) naturally present in many insects. If a female carrying a different strain - or not carrying - of the bacteria mates with a male carrying the selected strain, the eggs will not develop.
For the replacement technique, males and females infected with a strain of Wolbachia that reduces the mosquitoes' ability to transmit a virus are released to gradually replace local mosquitoes.
After analyzing the available international scientific studies, the French National Agency for Food Safety (ANSES) notes, for the sterile insect technique, "a proven level of proof for the reduction in the egg hatching rate in Aedes albopictus and probable in Aedes aegypti."
For its part, the incompatible insect technique has the capacity to "reduce the hatching rate of eggs and the number of females of the three Aedes species studied."
However, evidence "is lacking to determine whether these techniques can effectively reduce the incidence of vector-borne diseases," according to the agency.
The replacement technique, for its part, has a "proven" effect in reducing the incidence of dengue fever and a "possible" effect in reducing that of chikungunya.
To consolidate this assessment, the agency would like additional data to be collected.
Furthermore, possible "unintentional effects" of mosquito releases (appearance of resistance phenomena in insects, disruption of food chains, modification of the dynamics of virus transmission to humans, etc.), which have so far been "little documented", should be monitored, according to her.
As these releases are not currently governed by specific regulations, ANSES also recommends creating a regulatory status for irradiated insects or those carrying Wolbachia, making their declaration to a competent authority mandatory, and also assessing their social acceptability.
But these releases "cannot, on their own, eliminate the nuisances caused by Aedes mosquitoes or the risks of transmission," the agency emphasizes.
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