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Aedes aegypti is a vector for transmitting several tropical fevers. Only the female bites for blood, which she needs to mature her eggs. To find a host, these mosquitoes are attracted to chemical compounds emitted by mammals, including ammoniacarbon dioxidelactic acid, and octenol. Scientists at The United States Department of Agriculture (USDA) Agricultural Research Service have studied the specific chemical structure of octenol to better understand why this chemical attracts the mosquito to its host. They found the mosquito has a preference for "right-handed" (dextrorotatory) octenol molecules.
Although Aedes aegypti mosquitoes most commonly feed at dusk and dawn, indoors, in shady areas, or when the weather is cloudy, "they can bite and spread infection all year long and at any time of day."
Once a week, scrub off eggs sticking to wet containers, seal and/or discard them. The mosquitoes prefer to breed in areas of stagnant water, such as flower vases, uncovered barrels, buckets, and discarded tires, but the most dangerous areas are wet shower floors and toilet tanks, as they allow the mosquitos to breed in the residence. Research has shown that certain chemicals emanating from bacteria in water containers stimulate the female mosquitoes to lay their eggs. They are particularly motivated to lay eggs in water containers that have the correct amounts of specific fatty acids associated with bacteria involved in the degradation of leaves and other organic matter in water. The chemicals associated with the microbial stew are far more stimulating to discerning female mosquitoes than plain or filtered water in which the bacteria once lived.
Wear long-sleeved clothing and long trousers when outdoors during the day and evening.
Use mosquito netting over the bed if the bedroom is not air conditioned or screened, and for additional protection, treat the mosquito netting with the insecticide permethrin.
Insect repellents containing DEET (particularly concentrated products) or p-menthane-3,8-diol (from lemon eucalyptus) were effective in repelling Ae. aegypti mosquitoes, while others were less effective or ineffective in a scientific study. The Centers for Disease Control and Prevention article on "Protection against Mosquitoes, Ticks, & Other Arthropods" notes that "Studies suggest that concentrations of DEET above approximately 50% do not offer a marked increase in protection time against mosquitoes; DEET efficacy tends to plateau at a concentration of approximately 50%". Other insect repellents recommended by the CDC include Picaridin (KBR 3023/icaridin), IR3535, and 2-undecanone.
Although the lifespan of an adult Ae. aegypti is two to four weeks depending on conditions, the eggs can be viable for over a year in a dry state, which allows the mosquito to re-emerge after a cold winter or dry spell.
New research is looking into the use of a bacterium called Wolbachia as a method of biocontrol. Studies show that invasion of Ae. aegypti by the endosymbiotic bacteria allows mosquitos to be resistant to the certain arboviruses such as dengue fever and Zika virus strains currently circulating.
Distribution and population control efforts
Ae. aegypti mosquito distribution in the United States
The yellow fever mosquito's distribution has increased in the past two to three decades worldwide, and it is considered to be among the most widespread mosquito species. Signs of Zika virus-capable mosquito populations have been found adapting for persistence in warm temperate climates. Such a population has been identified to exist in parts of Washington, DC, and genetic evidence suggests they survived at least the last four winters in the region. One of the study researchers noted, " ...some mosquito species are finding ways to survive in normally restrictive environments by taking advantage of underground refugia". As the world's climate becomes predictably warmer, the range of Aedes aegypti and a hardier species originating in Asia, the tiger mosquito Aedes albopictus, which can expand its range to relatively cooler climates, will inexorably spread north and south. Sadie Ryan of the University of Florida was the lead author in a 2019 study published in PLOS Neglected Tropical Diseases that estimated the vulnerability of naïve populations in geographic regions that currently do not harbor vectors i.e., for Zika in the Old World. Ryan's co-author, Georgetown University's Colin Carlson remarked,"Plain and simple, climate change is going to kill a lot of people." The Northern Territory Government Australia and the Darwin City Council have recommended tropical cities initiate rectification programs to rid their cities of potential mosquito breeding stormwater sumps. A 2019 study published in Nature Microbiology found that accelerating urbanization and human movement would also contribute to the spread of Aedes mosquitoes.
Ae. aegypti has been genetically modified to suppress its own species in an approach similar to the sterile insect technique, thereby reducing the risk of disease. The mosquitoes, known as OX513A, were developed by Oxitec, a spinout of Oxford University. Field trials in the Cayman Islands, Jacobina Brazil, and Panama have shown that the OX513A mosquitoes reduced the target mosquito populations by more than 90%. This mosquito suppression effect is achieved by a self-limiting gene that prevents the offspring from surviving. Male modified mosquitoes, which do not bite or spread disease, are released to mate with the pest females. Their offspring inherit the self-limiting gene and die before reaching adulthood--before they can reproduce or spread disease. The OX513A mosquitoes and their offspring also carry a fluorescent marker for simple monitoring. To produce more OX513A mosquitoes for control projects, the self-limiting gene is switched off (using the Tet-Off system) in the mosquito production facility using an antidote (the antibiotic tetracycline), allowing the mosquitoes to reproduce naturally. In the environment, the antidote is unavailable to rescue mosquito reproduction, so the pest population is suppressed.
The mosquito control effect is nontoxic and species-specific, as the OX513A mosquitoes are Ae. aegypti and only breed with Ae. aegypti. The result of the self-limiting approach is that the released insects and their offspring die and do not persist in the environment.
In Brazil, the modified mosquitoes were approved by the National Biosecurity Technical Commission for releases throughout the country. Insects were released into the wild populations of Brazil, Malaysia, and the Cayman Islands in 2012. In July 2015, the city of Piracicaba, São Paulo, started releasing the OX513A mosquitoes. In 2015, the UK House of Lords called on the government to support more work on genetically modified insects in the interest of global health. In 2016, the United States Food and Drug Administration granted preliminary approval for the use of modified mosquitoes to prevent the spread of the Zika virus.
The recent invention of CRISPR/Cas9 based genome editing tool have significantly expanded the scope of genome editing research in Aedes aegypti mosquito. Several scientists across the globe have already attempted this technique to engineer the genome of vector mosquitoes. The genes like ECFP (enhanced cyan fluorescent protein), Nix (male-determining factor gene), Aaeg-wtrw (Ae. aegypti water witch locus), Kmo (kynurenine 3-monoxygenase), loqs (loquacious), r2d2 (r2d2 protein), ku70 (ku heterodimer protein gene) and lig4 (ligase4) were targeted to modify the genome of Aedes aegypti using CRISPR/Cas9 tool to obtain a new mutant, which will become incapable of pathogen transmission or result in population control.
Male (left) and female (center and right) Ae. aegypti
The species was first named (as Culex aegypti) in 1757 by Fredric Hasselquist in his treatise Iter Palaestinum. Hasselquist was provided with the names and descriptions by his mentor, Carl Linnaeus. This work was later translated into German and published in 1762 as Reise nach Palästina. Since the latter is an uncritical reproduction of the former, they are both considered to antedate the starting point for zoological nomenclature in 1758. Nonetheless, the name Aedes aegypti was frequently used, starting with H. G. Dyar in 1920.
Ae. aegypti feeding on a human
To stabilise the nomenclature, a petition to the International Commission on Zoological Nomenclature was made by P. F. Mattingly, Alan Stone, and Kenneth L. Knight in 1962. It also transpired that, although the name Aedes aegypti was universally used for the yellow fever mosquito, Linnaeus had actually described a species now known as Aedes (Ochlerotatus) caspius. In 1964, the commission ruled in favour of the proposal, validating Linnaeus' name, and transferring it to the species for which it was in general use.
The yellow fever mosquito belongs to the tribe Aedini of the dipteran family Culicidae and to the genus Aedes and subgenus Stegomyia. According to one recent analysis, the subgenus Stegomyia of the genus Aedes should be raised to the level of genus. The proposed name change has been ignored by most scientists; at least one scientific journal, the Journal of Medical Entomology, has officially encouraged authors dealing with aedile mosquitoes to continue to use the traditional names, unless they have particular reasons for not doing so. The generic name comes from the Ancient Greek , a?d?s, meaning "unpleasant" or "odious".
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