Welcome, kids, to the next module where we discuss the disease malaria. In the part 1, we talk about the causative agent, the transmission and the life cycle in the human host.
Now, when I talk about malaria, kids, this is a mosquito borne infectious disease, right, and who is the cause of organism. Yes, it is the Protist Plasmodium and this Plasmodium is commonly referred to as the ‘Malarial Parasite’. Now, if you talk about the incidents of malaria all over the world. If you see it is predominant in the tropical and sub-tropical regions, especially most of the Asia, the Sub Saharan Africa and South America, right.
Now, moving forward we said Plasmodium, right. There are about 4 species of Plasmodium that can infect humans and transmit this disease, right. So, which are they, number one is Plasmodium Falciparum then we have Plasmodium Vivax, Plasmodium Ovale and the last one is Plasmodium Malariae. Now remember, kids, amongst all these species, Flaciparum is the one that is going to cause the most severe form of malaria and we will see, why, okay.
Now, talking about the transmission of this disease, we said it is transmitted by the mosquito right. So, it is transmitted when an infected female Anopheles mosquito will bite human, right. Now, when this mosquito bites the human that is when the malarial parasite will enter human body, okay, and now therefore this becomes a vector mediated or a vector borne disease.
Now, kids, who told us the malaria is spread by mosquito bites. It is this great man here, Sir Ronald Ross. He was doctor in the Indian Army and he got a Nobel Prize for establishing the fact that malaria is caused by the bite of female Anopheles mosquito. How does this disease result? It is due to multiplication of the parasite within RBCs.
Now, kids, you saw that I am constantly stressing on the fact that it is the female Anopheles mosquito, right. So, remember that only and only female Anopheles mosquitoes feed on human blood. What about the males? The male Anopheles mosquitoes they feed on plant sap. So, do you think malaria will be transmitted because of the male Anopheles mosquitoes? Definitely not they will never spread the disease.
Now, talking about the life cycle of this Plasmodium parasite, it’s fairly a complicated one because it involves two hosts. One is the human host and human are the secondary host because asexual phase of the life cycle of Plasmodium takes place in humans. And who is the primary host, it’s the female Anopheles mosquito because the sexual reproduction of Plasmodium happens in the mosquito.
So, now let’s begin with the life cycle in human host. Now, let’s say an infected female Anopheles mosquito bites a human, right. So, in the saliva of the mosquito the Plasmodium is present, right. And therefore with the saliva of the mosquito we are going to be seeing the Plasmodium entering the human body, okay. And the form in which it enters is the Sporozoites form. Now, as soon as they enter the human body these Sporozoites, they migrate to that big organ up there which is the liver and then these Sporozoites infect the liver cells or Hepatocytes. Now, within the liver cells what is going to happen, these Sporozoites they start developing, they start multiplying, right, and they multiple into this form known as the Schizonts. And these Schizonts later on are going to develop and divide to form, what do you see here is the Merozoite. Now, remember Merozoite is the asexual Haploid form of Plasmodium. Now, these Merozoites from the liver cells they are going to rupture them, break open and come outside and they are going to enter into the blood stream and go into the RBCs. So, they infect the RBCs. Now, within the RBCs the Merozoites starts multiplying, right. So, they start multiplying initially into what you see the ring form. Now, some of the Merozoites they develop into what you going to see here that is the Gametocytes. Now, these Gametocytes will remain within the RBCs and majority of the ring forms they develop into the next form that is the Trophozoites form. And these Trophozoites further more divide to form more Schizonts and these Schizonts then divide to form more Merozoites and then these Merozoites from one RBC they break out and start infecting fresh, newer RBCs. So, you saw that within the RBCs what we are seeing is that the Plasmodium is multiplying in asexually, right. Merozoites in the RBC undergoing multiple fission, multiplying asexually forming the Schizonts which develop into more Merozoites and then these Merozoites go and infect fresh RBCs. So, now this happens over and over and over again, right, and several such cycles are going to keep happening. And kids, what is the one classical symptom of malaria? It is fever, right, the waves of fever that come. So, remember the waves of fever are because of the Merozoites escaping and infecting newer RBCs.
So, if we talk about the life cycle in human host. It’s divided into two phases. One is the infection of the liver which we call as Pre-Erythrocytic phase and the next one is the infection of RBCs which we call as the Erythrocytic phase, right.
Now, kids, with that we finish this module and I will be seeing you in the next module. Till then enjoy learning with Robomate.
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