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Current time:0:00Total duration:8:24

Video transcript

how is malaria diagnosed well we can think about it basically as a three-step process so remember that malaria is a disease caused by a parasite that's usually transmitted to humans through bites from infected mosquitoes so if we want to know if someone has malaria we might start by asking them if they've been bitten or if they've been to anywhere that infected mosquitoes are known to hang around like in certain tropical or subtropical countries we'd also double check to see if they were having any malaria symptoms like a flu-like illness or alternating chills and fevers that's sort of typical of a malaria illness so after we have this little conversation with the person right that's step one in our three-step process we would then move on to step two which is a physical exam so remember that malaria has two phases a liver phase where a whole bunch of sporozoites go in and infect the liver cells and then reproduce into thousands and thousands of marrows o lights and then there's a red blood cell phase where initially those same Marisa whites they burst out of your liver cells and they get into your bloodstream where they infect your red blood cells so in the physical exam well we kind of look for any clues on the outside of your body that might be able to tell us if these things are happening on the inside of your body so we know something might be going on in the liver right so we actually feel for the liver to see if it's enlarged because all of the inflammation that be happening if the liver cells were bursting or if they're infected that would make the liver in large a bit the other physical things we look for on a person mostly have to do with red blood cells so once the red blood cells start to get infected or once they start to get damaged right because of all these marrow sites that are infecting them these damaged red blood cells start to collect in the spleen which lives all the way over here beside the stomach and the spleen is responsible for screening our blood and sort of pulling out and recycling any old or damaged red blood cells so all of these damaged red blood cells are all of a sudden going to start filtering into the spleen and that'll cause some congestion in the spleen and you know there's also some inflammation happening in here too now so the spleen starts to enlarge starts to get bigger and in some cases it can enlarge really really massively so we try to feel for an enlarged spleen and remember red blood cells are bursting right and having lots and lots of nice healthy red blood cells as part of what gives us humans our nice warm coloring right to our skin so if we're losing lots of red blood cells we would start to go pretty pale so we look for pallor which just means abnormal paleness that happens when you don't have enough red blood cells circulating around and this power is easiest to see in the hands and in the face and then finally we might look for jaundice which will happen when Billy Ruben from inside the red blood cells get out and deposit under our skin good so that's step two that's our physical exam now on to step three this is the most specific the most definitive way of diagnosing malaria and it is a couple of lab tests so there's a few different tests we can do to diagnose malaria but I'll just describe the two most common ways so one way is by a blood smear so we take some blood from the person we stick it on a microscope slide you can see my nice microscope slide here with blood on it and then we look at it under a microscope to try to sort of directly visually pick out any malaria parasites right just using our own two eyes so you might have heard of a test called a thick and thin film and that's actually what this is here you can see that there's one sort of puddle of blood that's really thin and one the other puddle is a bit thicker right there's a bit more blood here and anytime we look at blood under a microscope we just call it a blood film so why do we need both the thick and the thin films well in the thick film we can zoom in a bit here this is our thick film if we were to look at it through a microscope this gives us a really broad view of the person's blood so there's a good amount of blood here that we can see all at once within our microscopes field of view so we're pretty quickly able to tell if it looks like there might be any parasites hanging around in there and indeed in this thick we can see that you know maybe that's a little Plasmodium there and maybe there's something going on over there and maybe over there again the main thing with this thick film is that we can look at lots at once to make sure we're getting a good representative sample of the person's blood but we don't get too much detail in a thick film and in fact remember that there's a couple different types of Plasmodium there's false sipper my backs there's Ovalle but we can't really differentiate them on a thick film we need our thin film for that so let's move over to our thin film and you can immediately see that it's a lot more detailed right because it's thin right it's basically just a single layer of blood cells they're not sort of all jumbled all over each other like in the thick film so we can see more detail and we can already see that there's some trophies alights in these red blood cells it's kind of weird but this used to be the marrow site that infected this red blood cell initially and now it's turned into a trophy Zoid which is what goes on to multiply into tons more marrow Zoids it reverts back to being called a marrow so I once it starts to reproduce and then here actually here's a red cell where that's already happened right this red cell is packed with marrow sites so we can definitely see that this person has a malaria parasite infection just by looking at the blood films and we can actually also pick out this false if M subtype of Plasmodium on the on this thin film and right here here's a vivax subtype so on the thin film we can tell the difference alright one last test we'll talk about so this one's called a rapid detection test or an R DT and this will give us our results in only about 15 minutes and you don't really need any training to do it whereas our thick and thin films although theoretically they could be done really quickly you need well first of all you need a microscope and second you need someone with a really skilled I to actually look at the blood films and these might not always be available so our D T's how do they work well essentially you take a drop of blood from usually a finger prick and then you actually collect the drop of blood with a special dipstick and this dipstick is really interesting it kind of works like the pregnancy tests that can test your urine to see if you're pregnant except obviously this is testing for malaria and hopefully using your blood and not your ear so here's a dipstick and on it there's all of these antibodies stuck all over its surface right and so these antibodies essentially look for two different things in the blood so let me set you up here so when red blood cells get infected with malaria parasites our red cells start to produce enzymes that end up being displayed they get stuck on to the outside of our red cell membranes and so some of the antibodies on the dipstick they'll be looking to grab on to any of these enzymes that they might be able to find in the blood sample right because that could mean that there's a Plasmodium infection one issue with that is that some of the enzymes only get produced in Plasmodium falciparum infections and not in infections by other types of Plasmodium and that's still usually okay because remember false supermum causes the vast majority of infections but in any case the dipstick also looks for something else so each subtype of Plasmodium produces a slightly different version of an enzyme that they all have called Plasmodium lactate dehydrogenase or p LD h so this is an enzyme that helps a Plasmodium make energy to do all of its dirty work and so our dipstick it actually has antibodies on it that can bind to each of the different p LD H's that the different subtypes of Plasmodium would make so based on the kind of p LD h that our dipstick antibodies bind to that's how we know what type of malaria parasite we're dealing with and that's important because some subtypes need their own special kind of treatment for us to completely remove them from our system