Satellite Rearing of Aedes Mosquito Eggs: Synchronized Empirical Test of a Novel Mass Rearing Model.

Mosquito suppression strategies based on "rear and release" of male mosquitoes are attracting renewed interest from governments, municipalities, and private businesses. These include irradiation-based sterile insect technique, Wolbachia-based technologies, and genetic modification. Each of these approaches requires the mass rearing and release of adult male mosquitoes, which typically is accomplished via a rearing facility near the release site. Although some release programs have relied on centralized rearing and shipment of adult males, adult male mosquitoes are relatively fragile, and their fitness can be diminished by temperature fluctuations, humidity, nutritional deficiencies, and other stresses that occur during shipment. Furthermore, expensive, expedited shipment is typically used to maximize the amount of adult lifetime in the field following the release. In contrast, Aedes aegypti and Ae. albopictus eggs can be desiccated and stored for long periods. They are small, and many millions of eggs can be shipped without specialized environmental conditions and using less expensive means. Here we examine a model in which mosquito eggs are centrally produced and then mailed to satellite rearing facilities. As a control, a replicate set of eggs was reared at the factory of origin. At each of the rearing sites, cloud-based software was used to track and compare rearing at the different locations. The results demonstrate similar rearing outcomes (i.e., egg hatch, immature development, and number of adult males) at each of the different sites for both species. We discuss the outcome in relation to downstream applications and potential future studies.

Laboratory Evaluation of Bigshot Maxim Against Three Species of Larval and Adult Mosquitoes, Aedes aegypti, Culex quinquefasciatus, and Anopheles quadrimaculatus.

The use of synthetic insecticides has been the main approach in mosquito control programs (MCPs) to prevent or reduce mosquito populations. The global problem of insecticide resistance and the concern of environmental impacts of synthetic insecticides have resulted in the interest of botanicals as an alternative. In this study, the botanical product BigShot Maxim, which contains cedarwood oil (14%), thyme oil (0.53%), and cinnamon oil (0.23%) as active ingredients, was examined in adulticide and larvicide bioassays against Aedes aegypti, Culex quinquefasciatus, and Anopheles quadrimaculatus. In the adulticide bioassay, 100% mortality was reached at a dilution of 1:10 after 4 h of exposure for all 3 species. In the larvicide bioassay, at the highest tested concentration (30 ppm by volume) the greatest mortality was 96.44 ± 1.44% SE for Ae. aegypti, 92.44 ± 2.07% SE for Cx. quinquefasciatus, and 33.33 ± 3.61% for An. quadrimaculatus, respectively. Insecticidal properties presented in all the experiments indicate that BigShot Maxim could be a viable alternative to some synthetic insecticides used in MCPs.

Evaluation of Lotions of Botanical-Based Repellents Against Aedes aegypti (Diptera: Culicidae).

Thirteen botanical product repellent compounds such as 2-undecanone, capric, lauric, coconut fatty acids (and their methyl ester derivatives), and catnip oil were formulated in either Coppertone or Aroma Land lotions and evaluated against laboratory-reared Aedes aegypti L. (Diptera: Culicidae) mosquitoes. These formulations contained 7-15 wt/wt of the botanical repellent as the major active ingredient either pure or as mixtures. USDA standard repellent test cages were used to determine the complete protection time (CPT) of the different formulated repellents. Two of the evaluated formulations, a 7% capric acid in Coppertone (CPT 2.7 ± 0.6 h) and 7% coconut fatty acids containing carrylic acid, capric acid, and lauric acid in Coppertone (CPT 2.3 ± 2.0 h), provided strong repellency against mosquitoes up to 3 h, which was equivalent to the (N,N-diethyl-m-toluamide) DEET control (CPT 2.7 ± 0.6 h). This work suggests future potential for these botanical product-based repellents as alternatives to commercial DEET-containing products.

Semi-field evaluation of a modified commercial My Mosquito Deleter larval trap with sticky paper against Aedes aegypti.

Aedes aegypti (L.) is a major vector of yellow fever, dengue, and Zika viruses, and its management can be difficult, especially in situations where insecticide usage is restricted and resistance is present. Traps and trapping techniques have mostly been used for monitoring populations of adult mosquitoes, but several commercially available traps have been evaluated and used to reduce nuisance populations of adult mosquitoes (Kline 2006). Suppression of Ae. aegypti, in particular, requires a suite of integrated control measures. One measure gaining more attention is to attract and kill gravid females by exploiting their oviposition behavior. Recently, a commercial larval trap for control of Culex mosquito larvae has been developed and marketed. The commercial brand name is My Mosquito Deleter (MMD; Destin, FL). When gravid female Culex mosquitoes lay their eggs in the MMD larval trap filled with water, the larvae after hatching from eggs will fall downward through the MMD's baffle system. The mosquito larvae cannot come to the surface due to the physical barrier from the baffle ring and black cone, resulting in larval mortality. During the preliminary experiment with the original MMD trap full of water, no adult mosquitoes were collected when larval mosquitoes were commonly recorded, because the gravid mosquitoes flew away after they laid their eggs. In order to catch gravid Aedes mosquitoes when they come to the trap to lay their eggs on water within the containers, we modified the MMD trap by placing sticky paper around the inside at the top of the trap (at the water line) after removing the baffle ring and lowering the water level to create an air pocket. The purpose of the study was to investigate the capability of a trap originally designed to trap Culex larvae to attract and kill gravid Ae. aegypti females with a simple and inexpensive modification by adding a piece of black sticky paper and lowering the level of water, in contrast to the unmodified MMD trap with a lower level of water.

Larvicididal Activity of Natural Repellents Against the Dengue Vector, Aedes aegypti.

The present research aimed to evaluate the larvicidal activity of several recently discovered natural repellents formulated in lotions against larvae of Aedes aegypti. We used a modified larval bioassay method by the World Health Organization standards in evaluating larval mortality at 24-, 48-, and 72-h exposure. Among the test repellents, 2-undecanone showed 100% mortality of Ae. aegypti larvae, followed by catnip oil, capric acid, coconut oil fatty acids, methyl caprate, methyl laurate, and coconut oil methyl esters. The repellent, 2-undecanone showed median lethal concentration (LC50) values of 73.07, 26.45, and 15.68 ppm at 24-, 48-, and 72-h exposure, respectively. Larvicidal activity varied among the other repellents tested.

Evaluation of boric acid as toxic sugar bait against resistant Aedes aegypti mosquitoes.

Current methods of broad area application of contact insecticides used in mosquito control are becoming less effective, primarily due to resistance within mosquito populations. New methods that can deliver ingestible insecticides are being investigated as a means to mitigate resistance. This study evaluated insecticide delivery through toxic sugar baits (TSB) and resulting mortality of susceptible and resistant strains of Aedes aegypti. Two Ae. aegypti strains were evaluated using a 1% boric acid TSB: the susceptible Orlando 1952 (ORL) strain and the resistant Puerto Rican (PR) strain. The TSB resulted in high mortality for both ORL and PR strain of Ae. aegypti. Average mortality of female mosquitoes given TSB was 90.8% for PR and 99.3% for ORL. Our study suggests that targeting resistant mosquitoes with ingestible insecticides through TSBs could be a viable alternative to current mosquito control strategies and should be considered when developing an integrated vector management program.

Impact of Three Species of Aquatic Plants on Anopheles quadrimaculatus and its Effect on the Efficacy of Boric Acid Sugar Baits.

The purpose of this study was to investigate the sugar-feeding behavior of Anopheles quadrimaculatus by measuring the impact of different aquatic plants on its survival. At the same time, the potential use of boric acid in toxic sugar bait (TSB) applications to the leaves of these plants was also evaluated. Mean survival rates of mosquitoes after 120 h feeding on 3 common aquatic plant species-Thalia geniculata, Pontederia cordata, and Limnobium spongia-were 10.55%, 1.86%, and 6.21%, respectively. No significant difference in mortality between mosquitoes feeding on separate plant species was detected (P = 0.05). The TSB efficacy was evaluated by leaf dip bioassay to compare 24-h mortality of mosquitoes feeding on leaves treated with TSB formulation (1% boric acid, 10% sucrose) and leaves dipped in 10% sucrose. Mortality was significantly higher for TSB-treated leaves for T. geniculata (t = 12.5, df = 8, P < 0.0001) and P. cordata (t = 5.42, df = 8, P = 0.0006) than for L. spongia (t = 1.4003, df = 8, P = 0.199). One-way ANOVA analysis showed no significant difference in efficacy between TSB-treated leaves of the 3 plants.