Ugh get out of here, leave you stupid mosquito.
I don’t want your stupid diseases!
hey guys Julia here for DNews
Mosquitoes are often seen as one of the most annoying creatures on this planet and arguably
one of the most deadly.
These buzzing nuisances carry deadly diseases like yellow fever, dengue fever, lymphatic
filariasis and, famously, malaria.
According to the World Health Organization, Malaria infects over 500 million a year and
kills 3 million.
So, why are mosquitoes such good carriers of disease, especially malaria?
Well interestingly #NotAllMosquitoes!
Of the 3,000 species of mosquitoes, only three seem to be the ones spreading most of the
human diseases we’re familiar with.
Anopheles mosquitoes carry malaria, filariasis, and encephalitis (an inflammation of the brain)
Culex mosquitoes carry encephalitis, filariasis, and the West Nile virus
and Aedes mosquitoes carry encephalitis, yellow fever and dengue fever
In fact many species of mosquito aren’t good carriers of disease at all!, According
to Dr. Kenneth D. Vernick, a microbiologist at the University of Minnesota, “most mosquitoes
are malaria-resistant and the susceptible ones are the oddballs."
Most mosquitoes actually fight malaria with their immune responses to parasites.
After a mosquito sucks up it’s bloody meal, a peritrophic matrix, (or barrier) forms in
between the bug’s lining of their midgut and the blood.
While it can take a few hours to form, it does trap some parasites inside, possibly
providing protection against some of them.
The malaria parasite doesn’t infect mosquitoes at all, it never enters their circulatory
system.
Another response mosquitoes have, is to coat the parasite in a melanin capsule, but this
comes at a cost.
The mosquito has to commit resources to coat the invader, which takes resources away from
things like reproduction, resulting in the infected mosquitoes becoming less fertile.
So though the parasite can enter the mosquitoes body, it often doesn’t make them sick.
Which is good for the parasite or virus.
Because if their host dies, they die too.
And malaria's next trick is getting from the mosquito into a human body.
Probably yours.
The parasite uses some of the very things that help a mosquito feed to easily enter
the next host.
Mosquitos have substances in their saliva that widen blood vessels, promote bleeding,
and shut down the human body’s natural first lines of defense.
These evolutionary advantages help invaders slip into their next host; with an injection
directly into the bloodstream, they bypass a lot of immune defenses.
And some parasites actually change a mosquito’s behavior to make it easier for them to achieve
this goal.
One study in PLOSone found that malaria makes humans smell more attractive to mosquitos.
And another study published in The American Journal of Tropical Medicine and Hygiene found
that malaria makes mosquitoes feed longer.
It invades the mosquito’s salivary (SAL UH VERY) glands while in the sporozoite (spore-oh-zoh-ite)
stage, which probably helps the parasite get into the next host easier.
But in their invasion, these young viruses interfere with the mosquito’s saliva production
which the mosquito needs to locate blood vessels in a host.
With impaired salivary abilities, it takes longer for the mosquitoes to feed to get the
same amount of blood.
Which is just fine with the parasite.
It gives them more time to jump to their new host!
So though mosquitoes are good at ferrying parasites like malaria to our bloodstream,
they don't benefit from their morbid task, and instead put themselves in more danger,
and can even become infertile.
The saying goes don’t kill the messenger, but in this case….you should totally kill
the messenger.
I agree with one cornell university researcher who called mosquitos “the most vile and
useless species on Earth.”
Why don’t we just get rid of them all?
Well Trace and Natalia find the answer in this episode right here.