Thread by @BugQuestions

For our last #DeepDive of 2018, let's talk about a mosquito that you'll be hearing a lot about in 2019.

Aedes aegypti is one of the most important disease vectors in the world.

So...what makes it a good vector, and why is it found worldwide?

Ae. aegypti is a mosquito that's originally from sub-Saharan Africa, adapted to living in the holes in trees.

This genus has a unique egg laying behavior. They lay their eggs on surfaces above water, and those eggs are dormant until the hole fills up.

flic.kr/p/8gXkQf

In it's home range, there are two color forms.

One color form is dark, and doesn't hang out around people.

The second is lighter colored, and pretty much specifically feeds on people.

It's that second one which more or less took over the world.

Ae. aegypti was well adapted to living around people initially. It's dormant eggs allowed it to hitch-hike on transatlantic journeys, around a food source that it was specifically adapted to eat.

So when the slave trade started up, Ae. aegypti was primed for worldwide invasion.

Yellow Fever had been known in Africa long before the Europeans; the first outbreak in the Americas was recorded in the mid-1600s.

It was a hugely consequential disease, disrupting everything from agriculture to the Panama Canal.

In fact, Yellow Fever stopped the PC for 100yrs,

We first figured out that Yellow Fever was spread by mosquitoes from this guy, Walter Reed.

In the 1870s, we thought it was spread through contact.

Walter Reed used mosquitoes fed on Yellow Fever victims to spread the disease to volunteers.

The study was actually ahead of it's time in some ways. This was the first recorded case of informed consent. Volunteers were told they could die.

...and some volunteers did die.

Clara Maass, below, died after being bitten by a second time to see if immunity happened.

So, Aedes aegypti became a worldwide mosquito because it was adapted to specifically feed on people, live around people, and hitch-hike all over the world.

It's also *really* good at resisting pesticides, too. Lots of pops are resistant to DDT, etc.

askentomologists.com/2017/04/25/ddt…

More recently, a second Aedes sp. has been giving Ae. aegypti a run for it's money in terms of invasion ability: Aedes albopictus.

Ae. albopictus is successful for many of the same reasons Ae. aegypti is, except one key difference.

flic.kr/p/MTG5dK

That difference is that Ae. albopictus is a generalist, whereas Ae. aegypti feeds on humans.

So, with Ae. aegypti...something like 80-90% of bites are on people.

With Ae. albopictus, that number can be as low as 10%.

Albo spreads disease, but we'd rather have that over aegypti

This is a mosquito that we've more or less accidentically domesticated. Ae. aegypti is exquisitely adapted to living around people, and has followed us all over the globe.

In most areas where it's found, it's an invasive species. It's only native to sub-Saharan Africa.

I'm writing this from the US, and a lot of our audience is outside the US.

scielo.br/scielo.php?pid…

If you want to learn more about the history of Ae. aegypti in your neck of the woods, this is an *excellent* article which covers most of the world outside my country.