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Video transcript

what is malaria and importantly why do I have this mosquito drawn here that seems a little bit weird well the mosquito here is actually pretty important malaria is a disease and infectious and often fatal disease that is transmitted to humans and other animals as well not just humans but it's transmitted most often by us being bitten by an infected mosquito and interestingly malaria is primarily a disease of the liver and of the red blood cells and as you'll sort of see in a few minutes here this kind of explains some of the symptoms that we see in malaria and we'll talk about those a little bit later on but first let me zoom in here and let's talk about what happens in a mosquito bite so here's our skin right and we'll say that these are blood vessels under the skin and here's our blood and out here is our friendly well not so friendly in this case but our mosquito and what is she doing here like why are mosquitoes always biting us well it's because they need to feed on blood in order to survive right they're like little flying vampires which incidentally is my personal worst nightmare so that's what she's doing around here she's trying to get at our blood by biting us real nice so to do that she will poke her little proboscis that's what this pointy mouth thing is called a proboscis through our skin to access all of our blood vessels underneath and from there she'll start to suck up some blood right and she'll start to fill up her little thieving tummy and then she'll take off all satisfied right she's happy and she goes off and and that's not usually a problem for us I mean I'm not advocating for mosquitoes here people get bitten by mosquitoes all the time and they're fine but some mosquitoes particularly ones that live in certain more tropical parts of the world right closer to the equator like some African countries and some Asian countries into some Latin American countries some mosquitoes the majority of which are in these areas carry a parasite called Plasmodium and there's a couple different types of Plasmodium for now we'll focus on Plasmodium falciparum falciparum because this type causes the highest number of deaths in humans alright so now let's add in some parasites to our mosquito here and see what happens when someone gets bitten by an infected mosquito and actually let me point out that I keep saying she when I talk about our mosquito here and that's because the Plasmodium parasite is usually transmitted by a female Anopheles mosquito Anopheles is just the genus and that's because females feed on blood while the male mosquitoes feed on other things like nectar from flowers and plants and such so how does she do it well once she's happily sort of drinking our blood some of the parasites from within her saliva they'll sort of swim over from inside her mouth to our bloodstream so that's kind of step one of the infection and what happens after that is that the parasites which are actually called sporozoites at this stage they have their own special name sporozoites and there's usually a whole bunch of them they swim through our bloodstream until they get to our liver and then they say to themselves hey this looks like a really fun place to hang out let's stay here for a while so they do they actually infect our liver cells and they they hang out in the liver for a couple weeks usually about two weeks and when they're in our liver cells they're not just passively hanging out there they're actually reproducing so they're a sexually reproducing and they're creating thousands of little parasite babies little offspring and so they reproduce and they reproduce and they reproduce for a couple of weeks until they build up this massive army of marrows a'ight so that's what they're called at a stage marrows o lights and when they're good and ready they burst out of our liver cells which obviously kills the liver so unfortunately and they enter back into the bloodstream and so this form of Plasmodium parasites they're going to go on and infect our red blood cells so they'll find red blood cells in our bloodstream not really too hard to do and from there they'll get inside them red their new home and you know from here things get even more interesting so some of the Mara sites they do exactly what they did in the liver cells they asexually reproduce they create tons and tons and tons of numeira sites which burst out of the red blood cells and go on to infect more red blood cells but another group of marrow sites once they infect a red blood cell they kind of shape-shift they do this really weird thing where they change form into what are called immature gummy toe sites and some will be male and some will be female and this will all make sense in a minute here so you'll just have to bear with me for a second and you'll see what these gamete asides do so what happens now well when we get bitten by yet another mosquito right these darn flying vampires whether they're infected or not there's a really good chance that while they're siphoning up our blood they're gonna suck up some of the red blood cells that contain these male and female gamete ascites and here's the really wild thing the gamete Oh sites need to actually be inside of mosquitoes gut to mature it's incredible so the male and the female gamete asides because of the I guess the sort of environment within a mosquitoes gut they fuse together to create a zygote and then this Plasmodium zygote goes on to develop into a new sporozoite remember the the initial infective form and then the sporozoite goes on and swims back up to the mosquitos salivary glands so now they're ready to be injected back into another human host it's incredible so this is sort of a really bizarre example of the circle of life probably not the kind of example you had in mind when you were watching The Lion King ad imagine so these Plasmodium parasites rely on both mosquitoes and some warm-blooded animal to reproduce unfortunately this group of warm-blooded animals includes us humans so before we wrap up I just want to briefly talk about the symptoms that you'd experience if you had a malaria infection so it generally takes about two weeks after being bitten by an infected mosquito or we start seeing any symptoms so why is that well remember that the Plasmodium sporozoites travel to the liver and hang out for a couple weeks so them hanging out is exactly what that couple-week asymptomatic period is but when they sort of burst out of our liver cells and then later on start to burst out of our infected red blood cells that's when we start to see the classic symptoms of malaria as we start to lose red blood cells and and as the immune system starts to take notice so when the immune system gets involved it kicks off a flu-like syndrome so just picture what you felt like when you last had the flu it's really similar to that but quite a bit more dangerous so things like really high fevers and headache and you know muscle pain and just generally feeling really unwell and there's actually a classic symptom associated with malaria called paroxysm temperature paroxysm where the person will sort of cycle between sudden coldness and shivering and fever and sweating and these paroxysmal symptoms they kind of come on and off about every 36 to 48 hours every couple days and that's because these symptoms are actually directly related to right they're representative of these waves of marrows Oh lights bursting out of the liver and the infected red blood cells that these staggered sort of cyclical times once they build up enough to launch a new wave essentially and remember how I said that red blood cells are getting destroyed well red blood cells inside them they have these proteins called bilirubin proteins and when they leak out into our bloodstream they tend to deposit under our skin and and just them being there gives our skin a bit of a yellowish tinge so this is known as hemolytic jaundice jaundice referring to the yellowing of the skin and hemolytic means the bursting of red blood cells which is why it's happening so the last thing I'll mention we classify an illness with malaria into two broad groups so uncomplicated and severe so uncomplicated malaria would in infection where a person has just these symptoms that I've described right flu-like symptoms with this paroxysm and maybe some jaundice and this type is pretty easily treated with medications there's anti malarial drugs that can kill off the Plasmodium parasites and the person can usually get back to being a hundred percent better but there's also a severe malaria which is when the person will also develop some serious organ problems like maybe some lung problems so they can't breathe properly or some circulatory problems like super low blood pressure or severe anemia because of all these blood cells that are up drink or they might develop some brain problems which might make the person really weak or might give them a really decreased level of consciousness so if a person has severe malaria they need to be taken to a hospital right away because in addition to the sort of standard anti malarial drugs they will likely need intensive care and constant monitoring to maximize their chances of survival