The Aedes Aegypti, or Yellow Fever Mosquito

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The Aedes aegypti mosquito is one of the most lethal organisms in human history. It is the main vector of several tropical diseases, including yellow fever, dengue fever, chikungunya, and the zika virus. The zika virus, in particular, has attracted attention due to that infection being implicated in an epidemic of babies being born with microcephaly, or unusually small heads in northeastern Brazil. Microcephaly is related to a number of health problems, including developmental delays, intellectual disabilities, and various lifelong health problems.

The A. aegypti mosquito isn’t the only species of mosquito that can spread the zika and other infections to humans. But the fact that this mosquito prefers to feed on people, and breeds near to where people live, has made it an extremely effective vector of human diseases. The A. aegypti often lays its eggs in man-made containers like open septic tanks, toilets, showers, and discarded urban trash that catches rainwater.

Because these mosquitoes prefer to feed on people, and because they usually breed in man-made habitats in densely-populated areas, they are particularly effective at spreading diseases to people. The anopheles mosquitoes that spread malaria tend to live in less densely-populated rural areas, preferring to lay their eggs in swampy or marshy areas rather than in man-made containers. The A. aegypti, on the other hand, are often called an “urban mosquito” because their preference for breeding in artificial containers near to places where people live.

The A. aegypti most likely originated in tropical Africa, and was spread to the Americas due to the Atlantic slave trade and triangular trade in the 17th century. The 1st recorded outbreak of yellow fever in the Americas, which was undoubtedly spread by this mosquito, took place in Barbados in 1647. A year later another outbreak was recorded in Mexico’s Yucatan Peninsula. In the centuries that followed, there were reoccurring outbreaks in ports and cities in the Americas and southern Europe, including one major epidemic in Philadelphia in 1793.

By spreading yellow fever, the A. aegypti altered world history. For example, yellow fever could determine the outcome of wars by decimating armies. When the British tried to invade Cartagena in Spanish-ruled New Granada in 1741, yellow fever killed many of their men and helped to ensure that they were defeated. British and French Napoleonic invasion forces in Saint-Domingue suffered similar fates in the 1790s and early 1800s during the Haitian Revolution. The A. aegypti mosquito also influenced the building of the Panama Canal. Frenchman Ferdinand de Lesseps tried, and failed, to build an Atlantic-Pacific canal across the Panama Isthmus in the 1880s and 1890s. This failure was partly due to the high death rate from yellow fever and malaria. The US took over the project after scientists discovered that yellow fever and malaria were transmitted by mosquitoes. By taking successful anti-mosquito measures, the Americans were able to successfully complete the Panama Canal.

This description of the A. aegypti mosquito was written by Leland Ossian Howard for the US government in 1913. Howard was the head of the US Bureau of Entomology in the early 20th century. Howard was involved in some of the early US government-sponsored research into the A. aegypti. Some of the information provided by Howard is outdated. For example, he calls that A. aegypti the “Aedes calopus”, assumes that it was native to the Americas , and that yellow fever was caused by protozoa like malaria . But his observations on the life stages and behavior of the A. aegypti mosquito are still accurate today.