Q.Is vaccine available against malaria ? Give reason for your answer.
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🔒 Start your 14-day free trial to unlock the full solution →Concept understanding — Life Cycle of Plasmodium (Malaria)
Malaria is caused by Plasmodium species — P. vivax, P. ovale, P. malariae and P. falciparum — each producing a distinctly named type of malaria with its own erythrocytic-cycle duration (48 hours for vivax/ovale, 72 hours for malariae, 36–48 hours for falciparum). It is transmitted only through the bite of an infected female Anopheles mosquito.
P. vivax is digenic: humans are the secondary host, the female Anopheles mosquito the primary host. The cycle has three phases — schizogony, gamogony and sporogony. A feeding mosquito injects sporozoites into the human bloodstream; these enter liver cells and undergo asexual schizogony (exo-erythrocytic schizogony), producing merozoites. Released merozoites invade RBCs and pass through early trophozoite and signet-ring stages into a schizont bearing yellow-brown Schuffner's granules; the schizont divides and the erythrocyte lyses, releasing fresh merozoites and haemozoin toxin — this erythrocytic cycle repeats roughly every 48–72 hours, producing the classic pattern of fever and chills (malarial paroxysms), driven partly by malarial toxins triggering macrophage release of TNF-α and interleukin. Some merozoites instead become macro- and micro-gametocytes; ingested by a mosquito, these fertilize in its gut to form a diploid zygote (ookinete), which develops on the gut wall into an oocyst and undergoes meiotic sporogony to yield sporozoites that migrate to the salivary glands, ready to restart the cycle at the next b …
Historically, no fully effective vaccine has been available against malaria because the causative parasite, Plasmodium, has an unusually complex life cycle with multiple developmental stages (sporozoite, merozoite, gametocyte) in both the mosquito and human host, and it also shows antigenic variation, constantly changing its surface proteins to evade the host's immune response - making it very difficult to design a single vaccine that targets it effectively. In 2021, the WHO approved RTS,S/AS01 (Mosquirix), the first malaria vaccine, but it gives only partial/moderate protection and is not a complete solution. …
No fully protective malaria vaccine has traditionally existed because Plasmodium's complex, multi-stage life cycle and antigenic variation make it hard to target, though a partially effective vaccine (RTS,S) is now available.
Malaria is caused by protozoan parasites of the genus Plasmodium, which have a complicated life cycle that alternates between the female Anopheles mosquito vector and the human host, passing through several morphologically and antigenically distinct stages - sporozoites (injected by the mosquito), liver-stage merozoites, blood-stage merozoites that infect red blood cells, and gametocytes (taken up by the mosquito). Because each stage expresses a different set of surface antigens, and the parasite can also alter these surface proteins (antigenic variation) to dodge the host's immune response, it has been extremely difficult to develop a single vaccine that provides strong, lasting immunity - unlike for many viral or bacterial diseases with simpler, stable antigens. For a long time this meant control relied mainly on vector control (mosquito nets, insecticides) and drug treatment rather than vaccination. More recently, the WHO recommended RTS,S/AS01 (Mosquirix) in 2021, and R21/Matrix-M more …
- CBSE 2025Set ANNUAL1 markQ.Fill in the blank: The malarial parasite requires two hosts ___ and mosquitoes to complete its life cycle.
›Reveal solutionSolution
Plasmodium completes its life cycle using humans as the intermediate host (asexual/liver and blood stages) and the female Anopheles mosquito as the definitive/primary host (sexual stage).
The malarial parasite Plasmodium multiplies asexually inside the human liver and red blood cells, causing the disease's symptoms, but its sexual cycle (production of gametes and sporozoites) occurs inside the gut of the f …
- CBSE 2025Set ANNUAL1 markMCQQ.The infective stage of malarial parasite in the salivary gland of mosquito is(a) Streptozoites(b) Sporozoites(c) Mesozoites(d) All of these
›Reveal solutionSolution
In the malaria parasite's (Plasmodium) life cycle, the sporozoite is the stage that develops in the mosquito's salivary glands and is infective to humans.
Within the female Anopheles mosquito, the malarial parasite undergoes sexual reproduction and sporogony, ultimately producing thousands of sporozoites that migrate to and accumulate in the mosquito's salivary glands. When the mosquito bites a human to take a blood meal, these sporozoites are injected into the bloodstream. They travel to …
- CBSE 2025Set ANNUAL1 markMCQQ.During the life cycle of Plasmodium, sexual reproduction takes place in :(a) Human(b) Female Anopheles mosquito(c) Male Anopheles mosquito(d) Both(a) and (b)
›Reveal solutionSolution
Sexual reproduction of Plasmodium (gamete formation and fusion) happens only inside the gut of the female Anopheles mosquito; in humans only asexual multiplication occurs.
The malarial parasite Plasmodium has two hosts:
- Human (intermediate host): only asexual reproduction (schizogony) takes place — first in liver cells, then repeatedly inside red blood cells. Rupture of infected RBCs releases merozoites and toxic haemozoin, producing the classic recurring chills and high fever of malaria. …
- CBSE 2025Set ANNUAL1 markMCQQ.Haemozoin is :(a) A toxin from Plasmodium species(b) A precursor of haemoglobin(c) A toxin from Haemophilus species(d) A toxin from Streptococcus
›Reveal solutionSolution
Haemozoin is a haemoglobin-breakdown pigment/toxin generated by the malarial parasite Plasmodium as it feeds on red blood cell contents.
When the malarial parasite (Plasmodium vivax, P. falciparum, etc.) infects red blood cells, it digests the host cell's haemoglobin as a nutrient source. This digestion releases free haem, which is toxic to the parasite; to detoxify it, the parasite polymerises the haem into an insoluble, inert pigment called haemozoin (also called malaria pigment). The periodic rupture of infected RBCs releases haemozoin along with other parasite metabolic products (collectively acting as toxins) into the bloodstream, which triggers the classic cyclical fever and chills of malaria. It is not …
- CBSE 2024Set D1 markMCQQ.In malaria, the product released by mosquito into blood that causes chill and fever:(a) Haematin(b) Schuffner's dots(c) Haemozoin(d) Haemotoxin
›Reveal solutionSolution
Rupture of RBCs by the malarial parasite releases the toxic pigment haemozoin into the blood, triggering chills and high fever.
Malaria is caused by the protozoan parasite Plasmodium (e.g., P. vivax, P. falciparum), transmitted by the bite of an infected female Anopheles mosquito.
Inside the human body, the parasite multiplies within red blood cells (the erythrocytic cycle). When a large number of RBCs rupture simultaneously (synchronously) to release a new generation of merozoites, they also release a toxic substance called haemozoin (a haemoglobin-breakdown pigment) into the bloodstream.
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- CBSE 2024Set ZOOLOGY1 markMCQQ.What is the infective stage of malarial parasite?(a) Sporozoite(b) Merozoite(c) Trophozoite(d) Gametocyte
›Reveal solutionSolution
The sporozoite, injected by the female Anopheles mosquito's bite, is the stage that infects humans with malaria.
The malarial parasite (Plasmodium) has a life cycle that alternates between the human host and the female Anopheles mosquito vector. When an infected female Anopheles mosquito bites a human, it injects thousands of sporozoites (formed in its salivary glands) into the person's blood. These sporozoites are the infective stage - they enter liver cells, multiply, and are then released into the blood as merozoites, which infect and rupture r …
- CBSE 2023Set ANNUAL1 markMCQQ.Exo-erythrocytic schizogony of Plasmodium takes place in :(a) Stomach(b) RBC(c) Liver(d) Leucocytes
›Reveal solutionSolution
Exo-erythrocytic schizogony of Plasmodium — the asexual multiplication stage occurring outside red blood cells — takes place in the liver.
When an infected female Anopheles mosquito bites a human, it injects sporozoites into the bloodstream. These sporozoites travel to and invade liver cells (hepatocytes), where they undergo asexual multiple fission called exo-erythrocytic schizogony, producing large numbers of merozoites. This 'exo-erythrocytic' (outside-RBC) stage is distinct from and precedes the erythrocytic cycle. Option (b) RBC is where the subsequent erythrocytic schizogony occurs (merozoites released from the liver invade red blood cells and cause the cyclical fever of malaria), not the exo-erythrocyti …
- CBSE 2022Set ANNUAL1 markMCQQ.Haemozoin is :(a) A toxin from plasmodium species(b) A precursor of haemoglobin(c) A toxin from haemophilus species(d) A toxin from streptococcus
›Reveal solutionSolution
Haemozoin is the pigment/toxin produced by Plasmodium (the malaria parasite) as a by-product of haemoglobin digestion, and its periodic release causes the characteristic fever of malaria.
When Plasmodium (the causative organism of malaria) multiplies inside human red blood cells, it digests the host cell's haemoglobin for nutrition; the leftover heme component is polymerised into an insoluble, dark pigment called haemozoin (also historically called malarial pigment). When the infected RBCs rupture to release a new brood of merozoites, haemozoin and other toxic metabolic products are released into the bloodstream, triggering the immune/febrile response responsible for the classic recurring chills and high fever of malaria. It is not a precursor of haem …
- CBSE 2020Set ANNUAL1 markQ.Why does the infection of malarial parasite cause fever in humans?
›Reveal solutionSolution
The rupture of red blood cells by the malarial parasite releases a toxin that triggers the body's fever response, producing malaria's classic cyclical chills and fever.
Plasmodium, the causative protozoan parasite of malaria, invades and multiplies inside the host's red blood cells (RBCs) in a repeating cycle. At the end of each cycle, the infected RBCs rupture synchronously, releasing newly formed parasites (merozoites) to infect fresh RBCs, along with a toxic pigment substance called haemozoin (a byproduct of the parasite's digestion of haemoglobin) and other cellular debris into the bloodstream. This sudden release triggers a strong immune/inflammatory response from the host's body, which manifests as the characteristic high fever accompanied by chills and shivering, recurring at regular intervals that correspond to the parasite's synchronised reproductive cycle ins …
- CBSE 2020Set ANNUAL1 markMCQQ.Find the true and false statements from the following :(i) Plasmodium vivax is a digenic parasite.(ii) The life cycle of Plasmodium involves 3 phases namely, schizogony, polygony and sporogony.(iii) The large schizont shows yellowish - brown pigmented granules called Schuffners granules.(iv) Plasmodium infection leads to Lysis of white blood cells results in cycles of fever and other symptoms.(a)(i) - True,(ii) - True,(iii) - False,(iv) - True(b)(i) - True,(ii) - True,(iii) - False,(iv) - False(c)(i) - True,(ii) - False,(iii) - True,(iv) - False(d)(i) - False,(ii) - True,(iii) - False,(iv) - True
›Reveal solutionSolution
Plasmodium vivax is genuinely digenetic and its cycle has three named phases (schizogony, gamogony, sporogony), but statements (iii) and (iv) contain factual errors.
(i) True -- Plasmodium vivax is a digenetic parasite, needing two hosts (the Anopheles mosquito and humans) to complete its life cycle. (ii) True, reading 'polygony' as the intended term 'gamogony' (gametocyte formation) -- the life cycle is classically described in three phases: schizogony (asexual multiplication in the human liver and red blood cells), gamogony/gametogony (formation of male and female gametocytes, beginning in humans), and sporogony (the sexual cycle completing in the mosquito's gut, producing sporozoites). (iii) False -- the yellowish-brown pigment granules seen in an infected red blood cell/schizont are malarial pigment (hemozoin), a haem-breakdown by-product; Schuffner's granules/dots are a separate, fine pink-red stippling seen in the cytoplasm of P. vivax-infected red blood cells, not the pigment inside the …
- CBSE 2016Set ANNUAL1 markMCQQ.Black water fever is caused by :(a) Plasmodium vivax(b) Plasmodium malariae(c) Plasmodium ovale(d) Plasmodium falciparum
›Reveal solutionSolution
Black water fever is a dangerous complication of Plasmodium falciparum malaria.
P. falciparum causes the most severe form of malaria; in some cases massive destruction of red blood cells releases so much haemoglobin that it darkens the urine — the condition called black water fever, which can also involve kidney damage. P. vivax, P. malariae and P. ovale cause milder …
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