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- Why can't male mosquito feed on human blood?(7 votes)
- Because only female mosquitoes require nutrients that are in the blood, since they need these nutrients for the maturation of the eggs they carry. It's like a pregnancy diet for them, if they don't have the blood, their eggs will not become healthy and mature to release new baby mosquitoes. The male doesn't carry the eggs so he doesn't need these nutrients, then he preffers fruits and nectar from flowers :) hope it was helpful(19 votes)
- why mosquito do not infected by the plasmodium or malarial parasite?(4 votes)
- For the plasmodium: the sporozoites do not come in direct contact of circulatory system of mosquito while in human directly come in contact with circulatory system and then to hepatocytes therefore it does not infect mosquito but humans.
More over you think it as vector-host relationship, A pathogen that makes a mosquito "sick" (reduces activity or increases mortality) will generally get transmitted less, so there is strong selective pressure not to do this. However, some behaviors increase pathogen transmission despite making things more dangerous for the vector, like feeding more frequently. Several pathogens (including Plasmodium) are known to affect the behavior of infected vectors in exactly this way. There's another example in this recent paper: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0063602).(9 votes)
- Hiya, How does the parasite get to the liver without being detected by our immune system? Thanks!(5 votes)
- Hi Sophia, that's an excellent question and something a lot of people are still figuring out.
There are two branches of the human immune system; the innate and the adaptive system. The innate system can be activated immediately but it is not very specific and can't clear everything. Some parasites survive and are transported to the liver where they are able to hide from the immune system inside liver cells - a clever strategy!
The other arm of the immune system, the adaptive immune system, is actually capable of clearing most of the parasites but this takes time. In that time, the parasite is able to change its outer proteins and 'escape' the adaptive immune system. So you get this cat and mouse game where the immune system gets rid of most of the parasites, but they change their proteins, escape, and start dividing again!
If you want a more thorough explanation, here is a link to a recent open access paper looking at how P. falciparum escapes our immune system: http://file.scirp.org/pdf/AID_2016062815164090.pdf(7 votes)
- how do merozoites go inside a red blood cell(3 votes)
- It's a pretty complicated 5 step process
1. merozoites bind to the surface of RBC's using a MSP-1 (a protein that binds to band 3 on red blood cells)
2. They reorient themselves with AMA-1 so their microneme is in contact with the RBC
3. They form a junction with the RBC by producing proteins (either EBA-175 or Duffy protein depending on the strain of Plasmodium)
4. Rhoptry proteins clear out the proteins in the RBC, pushing themselves inside without ever rupturing the cell at any point
5. The vacuole created (parasitophorous vesicle) closes around the Plasmodium, creating a pocket in the RBC for the merozoite to develop into trophozoites, then either more merozoites or gametocytes.(4 votes)
- why do the sporozoites first attack the liver not the RBCs
is that cause RBCs can be infected only with the merozoites?
pls help...(3 votes)
- Yes! You almost got it. The sporozoites need somewhere to reproduce asexually without detection, and in the liver is a prime spot. Once they've been made, and are mature enough, then, and only then can they infect the RBC's.(3 votes)
- What type of liver cells do the sporozoites attack? Epithelium?(2 votes)
- can animals receive malaria too or is it only with humans(1 vote)
- Animals, birds, reptiles, rodents, can be infected with a type of malaria that is specific to that species. In other words, a region can have mosquitoes that are vectors for avian malaria and not human malaria. The good news is we have animals that can serve as models to help us learn how to eliminate plasmodium, for example. The bad news is that some of the life cycle details are also specific to the species of plasmodium and not completely transferable to the malaria species that infect people. However it is helpful that we can observe what happens in rodents or birds infected with malaria in the laboratory. https://malariajournal.biomedcentral.com/articles/10.1186/s12936-016-1451-y(3 votes)
- umm...i think the part where its said that mosquito suck blood to survive is wrong.. they suck blood,because they need the blood of warm blooded animals to develop their eggs :D they dont suck blood for survival. they do it for reproduction :D(2 votes)
- why does the plasmodium parasite need to undergo a sexual mode of reproduction? and why does it need the mosquito for this, why cant it be completed in humans?(2 votes)
- [Voiceover] 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, an 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, the 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 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, and some, some Latin American countries, some mosquitoes, the majority of which are in these areas, carry a parasite called plasmodium. And there is a couple of different types of plasmodium, but for now, we'll focus on Plasmodium falciparum, falciparum, because this type causes the highest number of deaths in humans. All right. 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 hang out in the liver for a couple of weeks, usually about two weeks. And when they're in our liver cells, they're not just passively hanging out. They're actually reproducing. So, they're asexually 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 merozoites. That's what they're called at this stage, merozoites. And when they're good and ready, they burst out of our liver cells, which obviously kills the liver cell, unfortunately, and they enter back into the bloodstream. And so, this form of plasmodium, merozoites, 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 cells are their new home. And, you know, from here, things get even more interesting. So, some of the merozoites, they do exactly what they did in the liver cells. They asexually reproduce. They create tons and tons and tons of new merozoites, which burst out of the red blood cells and go on to infect more red blood cells. But another group of merozoites, 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 gametocytes, 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 gametocytes 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 going to suck up some of the red blood cells that contain these male and female gametocytes. And here's the really wild thing. The gametocytes need to actually be inside a mosquito's gut to mature. It's incredible. So, the male and the female gametocytes, because of the, I guess, the sort of environment within a mosquito's gut, they fuse together to create a zygote. And then this plasmodium zygote goes on to develop into a new sporozoite. Remember, the initial infective form? And then, the sporozoite goes on and swims back up to the mosquito's 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, I'd 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, generally, it takes about two weeks after being bitten by an infected mosquito before 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 of weeks. So, them hanging out is exactly what that couple of 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 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 fever 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 of days. And that's because these symptoms are actually directly related to, right, they're representative of these waves of merozoites bursting out of the liver and the infected red blood cells at 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 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 be an 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 problem, 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 rupturing, 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.