Boosting the sterile insect technique with pyriproxyfen increases tsetse flies Glossina palpalis gambiensis sterilization in controlled conditions

Abstract

Tsetse flies (Diptera: Glossinidae) are the main vectors of animal and human trypanosomoses in Africa. The Sterile Insect Technique (SIT) has proven effective in controlling tsetse flies when applied to isolated populations but necessitates the production of large numbers of sterile males. A new approach, called boosted SIT, combining SIT with the contamination of wild females by sterile males coated with biocides has been proposed for large-scale control of vector populations. The aim of the study was to evaluate this new approach using pyriproxyfen on the riverine species Glossina palpalis gambiensis (Vanderplank, 1949) in the laboratory. The contamination dose and persistence of pyriproxyfen on sterile males, the impact of pyriproxyfen on male survival, and the dynamics of pyriproxyfen transfer from a sterile male to a female during mating, as well as the impact of pyriproxyfen on pupal production and adult emergence, were evaluated in the laboratory. For this purpose, a method of treatment by impregnating sterile males with a powder containing 40% pyriproxyfen has been developed. The results showed that the pyriproxyfen has no impact on the survival of sterile males. pyriproxyfen persisted on sterile males for up to 10 days at a dose of 100 ng per fly. In addition, the horizontal transfer of pyriproxyfen from a treated sterile male to a female during mating could be measured with an average of 50 ng of pyriproxyfen transferred. After contacts without mating, the average quantity transferred was more than 10 ng. Finally, the pyriproxyfen powder was very effective on G. p. gambiensis leading to 0% emergence of the pupae produced by contaminated females. These promising results must be confirmed in the field. A large-scale assessment of this boosted pyriproxyfen-based SIT approach will be carried out against tsetse flies in Senegal (West Africa).

Larviposition site selection mediated by volatile semiochemicals in Glossina palpalis gambiensis

“…The aggregation behaviour described in the present study may be taken into account as an additional aid for this method as it may lead to the contamination of larval sites, as described in mosquitoes (Pleydell & Bouyer, 2019). Indeed, after contacts between impregnated sterile males and females but without mating, biocide is transferred to the female that will be thereafter released in the larviposition site (Laroche et al ., 2020). Therefore, female larviposition behaviour may increase the impact of boosted SIT through the contamination by progeny of other females, thereby enhancing control strategies.…”

Sex-specific sub-lethal effects of low virulence entomopathogenic fungi may boost the Sterile Insect Technique

“…For example, in the case of tsetse flies, sterilized males can be impregnated with pyriproxyfen, an insect growth regulator molecule that inhibits larval development (Sullivan and Goh, 2008). Laboratory studies have shown that these males can transfer this insect growth regulator to females for up to ten days through simple contact, even if mating fails, effectively preventing them from producing viable offspring (Laroche et al, 2020). Mathematical and agent-based modelling identified the conditions of where field efficacy may be greater than for classical SIT (Diouf et al, 2022; Haramboure et al, 2020; Pleydell and Bouyer, 2019).…”