Aquatain® causes anti-oviposition, egg retention and oocyte melanization and triggers female death in Aedes aegypti

Abstract

Background In arboviral disease systems where the virus can be transmitted from male to female vectors and from one generation to the next, targeting the female (especially when she is gravid) can help alter the persistence of the virus in nature and its transmission. A typical example is Aedes aegypti, which has become unmanageable due to the development of insecticide resistance. Despite evidence that monomolecular surface films prevent the selection of genetic resistance, their potential in Aedes vector control remains largely unexplored. Methods We examined the oviposition, egg retention, oocyte melanization, and female mortality of the Cayman Islands strain of Ae. aegypti, using choice (balanced and unbalanced) and no-choice bioassays involving Aquatain® Mosquito Formulation (AMF; Aquatain Products Pty Ltd.), a polydimethylsiloxane–based liquid used for mosquito control. Results When presented with similar opportunities to oviposit in two sites treated with AMF and two other sites with untreated water (control), egg deposition rates were significantly higher in the untreated water sites than in the AMF-treated sites (P < 0.05). We also observed a matching pattern of egg deposition preference in environments with more options in terms of AMF-treated sites. Females laid significantly more eggs when water was the only available medium than when all sites were treated with AMF (P < 0.05). Also, significantly more mature eggs were withheld in the AMF no-choice environment than in the no-choice test involving only water (P < 0.05). Internal oocyte melanization was not observed in females from the oviposition arenas with the lowest AMF presence (equal-choice and water-based no-choice); in contrast, this physiological response intensified as the number of AMF-treated sites increased. Female death occurred at high rates in AMF-treated environments, and this response increased with the increasing presence of such egg deposition sites. Conclusions This study demonstrated that AMF acted as a deterrent signal to ovipositing Ae. aegypti and as an indirect adulticide. These results suggest that AMF may be a promising control tool against the dengue vector, and this warrants further evaluation under field settings. Graphical Abstract

Toxicity, Ovipositional Behaviour and Electrophysiological Response of Rice Moth <i>Corcyra cephalonica</i> (Stainton) Adults to Essential Oils

“…The reduced (Papachristos and Stamopoulos, 2002). The negative physiological and behavioural impacts, egg resorption and structural alterations in the follicle were reported to cause egg retention (Dieng et al, 2022). E. citriodora and O. basilicum EOs recorded reduced egg production, which might be attributed to the altered respiratory patterns, repellence and behavioural changes brought about by exposure to essential oils (Correa et al, 2015;Silva et al, 2017).…”

Drones for Area-Wide Larval Source Management of Malaria Mosquitoes

“…On the other hand, we used a commercial drone platform (the Agras MG-1 S), normally used for precisionspraying of crops, to apply AMF on mosquito larval habitats. AMF is a commercially available surface film, with polydimethylsiloxane (PDMS) as its major constituent, with known lethal physical action against the aquatic stages of mosquitoes [36][37][38]. AMF obtained WHO prequalification in December 2018 and is now included as a larvicide for use by the UN and other organizations and countries [39].…”