Aedes aegypti Controls AE. Aegypti: SIT and IIT-An Overview.

The sterile insect technique (SIT) and the incompatible insect technique (IIT) are emerging and potentially revolutionary tools for controlling Aedes aegypti (L.), a prominent worldwide mosquito vector threat to humans that is notoriously difficult to reduce or eliminate in intervention areas using traditional integrated vector management (IVM) approaches. Here we provide an overview of the discovery, development, and application of SIT and IIT to Ae. aegypti control, and innovations and advances in technology, including transgenics, that could elevate these techniques to a worldwide sustainable solution to Ae. aegypti when combined with other IVM practices.

Point Protection with Transfluthrin against Musca domestica L. in a Semi-Field Enclosure.

House flies are notoriously difficult to control, owing to their tendency to live in close relationships with humans and their livestock, and their rapid development of resistance to chemical controls. With this in mind, we explored an alternative chemical control, a spatial repellent to deter Musca domestica L. from points we wanted to protect (i.e., a baited trap). Our results demonstrated that the synthetic spatial repellent, transfluthrin, is effective in preventing M. domestica adults from entering protected traps for both a susceptible strain (CAR21) and a field-acquired permethrin-resistant strain (WHF; 24 h LD50 resistance ratio of 150), comprising 22% and 28% of the total number of flies collected, respectively. These results are promising and demonstrate that transfluthrin can be an effective spatial repellent to protect points of interest where needed.

Transfluthrin diffusers do not protect two-person US military tents from mosquitoes in open field and canopy warm-temperate habitats.

Spatial repellents are volatile or volatilized chemicals that may repel arthropod vectors in free space, preventing bites and reducing the potential for pathogen transmission. In a 21-week field study, we investigated the efficacy of passive transfluthrin-impregnated diffusers placed in two-person United States (US) military tents located in canopy and open field habitats in north Florida to prevent mosquitoes from entering. Mosquito collections with US Centers for Disease Control and Prevention traps baited with light and carbon dioxide were conducted weekly for weeks 0-4, every two weeks for weeks 5-10, and monthly for weeks 11-21. Our results demonstrated that these transfluthrin-impregnated devices did not function as spatial repellents as expected and did not create a mosquito-free zone of protection. Instead, we observed consistently higher collections of mosquitoes from tents with transfluthrin-impregnated diffusers, and higher rates of mosquito mortality in collections from tents with transfluthrin diffusers, compared to untreated control tents. Based on these findings we do not recommend the use of passive transfluthrin-impregnated diffusers for mosquito protection in two-person US military tents in warm-temperate environments similar to north Florida.

Gamma-Irradiated Female Aedes aegypti Mosquitoes Exhibit Greater Susceptibility to Mayaro Virus.

Mayaro virus (MAYV) is an alphavirus endemic in many parts of Central and South America transmitted to humans by Aedes aegypti. Currently, there is no vaccine or treatment of Mayaro infection, and therefore it is essential to control transmission by reducing populations of Ae. aegypti. Unfortunately, Ae. aegypti are extremely difficult to control with traditional integrated vector management (IVM) because of factors such as growing resistance to a dwindling list of registered insecticides and cryptic immature and adult habitats. The sterile insect technique (SIT) by irradiation is gaining traction as a novel supplemental tool to IVM. The SIT is being used operationally to release large numbers of sterilized colony-reared male mosquitoes in an intervention area to overwhelm females in the natural population, eventually causing population decline because of high frequencies of unfertilized eggs. However, little is known about the effect of irradiation on vector competence for mosquito-borne viruses such as MAYV in females that may be accidentally reared, irradiated, and released alongside males. In this investigation, we exposed female Ae. aegypti pupae to radiation and evaluated vector competence after inoculation with MAYV. Infection and dissemination rates of irradiated (10 and 40 Gy) Ae. aegypti were higher than those of non-irradiated cohorts at 7 and 14 days after infection. Although these results indicate a need to maintain effective sex sorting prior to irradiation and release of Ae. aegypti, our results are consistent with several previous observations that vectorial capacity and vector competence are likely lower in irradiated than in nonirradiated females.

Climate-disease connections: Rift Valley Fever in Kenya

Entre 1950 e 1998 houve surtos de febre no Vale do Rift, no Quênia, após períodos de aumentos pluviométricos anormais. Em escala interanual, esses períodos estiveram associados à fase quente do fenômeno ENSO (El Niño/Southern Oscillation) na Africa Oriental. As chuvas alagam os criadouros de mosquitos - dambos -, cujos ovos, infectados pela via transovariana, eclodem, produzindo mosquitos Aedes, transmissores do vírus da febre do Vale do Rift aos seres humanos e, em especial, ao gado. A análise dos dados históricos sobre surtos de febre do Vale do Rift e indicadores do fenômeno ENSO - incluindo temperaturas superficiais dos Oceanos Pacífico e Indico e o Indice de Oscilaçäo Sul - mostrou que mais de 75 por cento dos surtos ocorreram em períodos quentes do ENSO. Na época estudada - 1981-1998 -, o mapeamento das condiçöes ecológicas via satélite (NDVI) - com dados normalizados sobre diferenças na vegetaçäo - evidenciou que as áreas de surto apresentaram desvios anômalos na intensidade do verde da vegetaçäo (indicador de pluviosidade alta), em particular, nas regiöes áridas da Africa Oriental - as mais afetadas pela febre. Os resultados indicam associaçäo estreita entre variabilidade climática interanual e surtos de febre do Vale do Rift no Quênia.

Further evaluation of Indoor resting boxes for aedes aegypti surveillance.

Several types, locations and intervals of artificial resting boxes were evaluated for their ability to attract Aedes aegypti males and females resting in houses in Thailand. Overall, 34% of both male and female Ae. aegypti captured resting inside houses were collected from the resting boxes. Boxes with black cloth strips covering the entrance attracted the same number of males and females as boxes without strips. There was no significant difference between the mean number of females collected in small resting boxes, with an inside surface area of about one-fifth the surface area of the larger boxes, and the larger boxes. However, significantly, fewer males were collected in the smaller box. The length of time during which the box was placed in the house prior to sampling, either a 15-17-hour interval from evening to the next morning or a 3-4- hour interval in the morning, had no effect on the number of mosquitoes collected. The position where the box was located in the house had more effect on the number of females resting in the box than it did on the number of males. Boxes placed in the dark corners of the house attracted more resting females than those placed in the lighted, open areas, usually in the middle of the house; however, the differences were not significant. The findings further confirm that resting boxes are practical for use in routine sampling of Ae. aegypti inside houses. Small boxes can be transported conveniently and are as efficient for collecting females as larger boxes. Boxes can be placed in lighted or dark areas of a house for as little as 3-4 hours to sample the Ae. aegypti house population.