Integration of irradiation with cytoplasmic incompatibility to facilitate a lymphatic filariasis vector elimination approach

Background. Mass drug administration (MDA) is the emphasis of an ongoing global lymphatic filariasis (LF) elimination program by the World Health Organization, in which the entire 'at risk' human population is treated annually with anti-filarial drugs. However, there is evidence that the MDA strategy may not be equally appropriate in all areas of LF transmission, leading to calls for the augmentation of MDA with anti-vector interventions. One potential augmentative intervention is the elimination of vectors via repeated inundative releases of male mosquitoes made cytoplasmically incompatible via an infection with Wolbachia bacteria. However, with a reduction in the vector population size, there is the risk that an accidental female release would permit the establishment of the incompatible Wolbachia infection type, resulting in population replacement instead of population elimination. To avoid the release of fertile females, we propose the exposure of release individuals to low doses of radiation to sterilize any accidentally released females, reducing the risk of population replacement. Results. Aedes polynesiensis pupae of differing ages were irradiated to determine a radiation dose that results in sterility but that does not affect the survival and competitiveness of males. Laboratory assays demonstrate that males irradiated at a female sterilizing dosage of 40 Gy are equally competitive with un-irradiated males. No effect of irradiation on the ability of Wolbachia to affect egg hatch was observed. Conclusion. An irradiation dose of 40 Gy is sufficient to cause female sterility, but has no observed negative effect on male fitness. The results support further development of this approach as a preventative measure against accidental population replacement.