Operational use of household bleach to "crash and release" Aedes aegypti prior to Wolbachia-infected mosquito release.

Dengue (family Flaviviridae, genus Flavivirus, DENV) remains the leading arboviral cause of mortality in the tropics. Wolbachia pipientis has been shown to interrupt DENV transmission and is presently being trialled as a biological control. However, deployment issues have arisen on methods to temporarily suppress wild mosquito populations before Wolbachia-infected mosquito releases. By suppressing wild populations, fewer Ae. aegypti releases are required to achieve a sustainable Wolbachia density threshold. Furthermore, public distress is reduced. This study tests the application of domestic bleach (4% NaCIO) to temporarily "crash" immature Aedes populations in water-filled containers. Spray application NaClO (215 ppm) resulted in a mean 48-h mortality of 100, 100, 97, and 88% of eggs, second-instar larvae, fourth-instar larvae, and pupae, respectively. In the field, NaClO delayed ovipositing by 9 d in cooler months, and 11 d in hotter months, after which oviposition resumed in treated receptacles. We found bleach treatment of pot-plant bases did not cause wilting, yellowing, or dropping of leaves in two ornamental plants species. Domestically available NaClO could be adopted for a "crash and release" strategy to temporarily suppress wild populations of Ae. aegypti in containers before release of Wolbachia-infected mosquitoes. The "crash and release" strategy is also applicable to other mosquito species, e.g., Aedes albopictus (Skuse), in strategies using released mosquitoes.

Sampling biases of the BG-sentinel trap with respect to physiology, age, and body size of adult Aedes aegypti (Diptera: Culicidae).

Currently, Aedes aegypti (L.) control strategies are being developed that involve manipulation of the vector at the adult stage (e.g., the use of the bacterial endosymbiont Wolbachia to shorten the life span of the vector population). These novel strategies demand adult sampling methods to measure changes in population size, structure (age, sex ratio), and, ultimately, the success of the program. Each sampling method presents certain biases. Once these biases are defined, methods used to estimate population size and structure can be calibrated accordingly, resulting in more accurate and complex estimates of the vector population. A series of mark-release-recapture experiments with adult Ae. aegypti were conducted in a large outdoor flight cage and an indoor setting in far north Queensland, Australia. The biases of the BG-Sentinel trap (BGS) were investigated across several categories, as follows: 1) mosquito age; 2) sex; 3) physiological status; and 4) body size. Biases were not detected across age groups or body sizes. A significant bias was detected across physiological groups: nulliparous females were recaptured at a significantly lower rate than all other groups except blood-fed parous females, which were also recaptured at a low rate by the BGS. Males were recaptured at a higher rate than all groups, but only a significant difference in recapture rates was observed between males and nulliparous females. Previous studies show that the BGS is a highly effective tool for Ae. aegypti surveillance. The BGS proves to be a reliable tool in Ae. aegypti surveillance with consistent sampling outcomes. The sampling bias of the BGS is measurable and can be used to generate more accurate estimates of the adult population and its attributes.

Evaluation of BG-sentinel trap trapping efficacy for Aedes aegypti (Diptera: Culicidae) in a visually competitive environment.

The BG-Sentinel (BGS) trap uses visual and olfactory cues as well as convection currents to attract Aedes aegypti (L.). The impact of the visual environment on trapping efficacy of the BGS trap for Ae. aegypti was investigated. Four- to 5-d nulliparous female and male Ae. aegypti were released into a semicontrolled room to evaluate the effect of the presence, reflectance, and distribution of surrounding harborage sites on BGS trapping efficacy. Low-reflective (dark) harborage sites near the BGS had a negative effect on both male and nulliparous female recapture rates; however, a more pronounced effect was observed in males. The distribution (clustered versus scattered) of dark harborage sites did not significantly affect recapture rates in either sex. In a subsequent experiment, the impact of oviposition sites on the recapture rate of gravid females was investigated. Although gravid females went to the oviposition sites and deposited eggs, the efficacy of the BGS in recapturing gravid females was not compromised. Ae. aegypti sampling in the field will mostly occur in the urban environment, whereby the BGS will be among oviposition sites and dark harborage areas in the form of household items and outdoor clutter. In addition to understanding sampling biases of the BGS, estimations of the adult population size and structure can be further adjusted based on an understanding of the impact of dark harborage sites on trap captures. Outcomes from this suite of experiments provide us with important considerations for trap deployment and interpretation of Ae. aegypti samples from the BGS trap.

Evaluation of three traps for sampling Aedes polynesiensis and other mosquito species in American Samoa.

The efficacy of the recently developed BG-Sentinel mosquito trap baited with BG-Lure (a combination of lactic acid, ammonia, and caproic acid) was evaluated in American Samoa against the omnidirectional Fay-Prince trap and the Centers for Disease Control and Prevention (CDC) light trap, both baited with carbon dioxide. The BG-Sentinel trap captured the greatest number of the important filariasis and dengue vector Aedes (Stegomyia) polynesiensis at all 3 collection locations; however, its catch rate was not significantly different from that of the Fay-Prince trap at 2 of the 3 trapping locations. The CDC light trap caught very few Ae. polynesiensis. The Fay-Prince trap was more efficient than the other 2 traps for collecting Aedes (Aedimorphus) nocturnus, Aedes (Finlaya) spp., Culex quinquefasciatus, and Culex annulirostris. The efficacy and convenience of the BG-Sentinel suggest further research is warranted to evaluate its potential as a possible efficient and safe alternative to landing catches for sampling Ae. polynesiensis in research and control efforts against filariasis and dengue in the South Pacific.