Plasmodium and Malaria Overview
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Questions and Answers

What is the primary function of the apicoplast in Plasmodium?

  • Energy production
  • Host cell invasion
  • Nutrient synthesis (correct)
  • Regulating temperature

Plasmodium species are exclusively found in humans.

False (B)

Name one of the five secretory/structural organelles that make up the apical complex in Plasmodium.

Rhoptries

The life cycle of Plasmodium involves three distinct processes: sporogony, merogony, and __________.

<p>gametogony</p> Signup and view all the answers

Match the following Plasmodium species with their associated characteristics:

<p>P.falciparum = Most severe malaria P.vivax = Relapsing malaria P.malariae = Quartan malaria P.ovale curtisi = Similar to P.vivax</p> Signup and view all the answers

Which of the following structures contributes to the attachment and invasion of host cells by Plasmodium?

<p>Micronemal adhesion proteins (A)</p> Signup and view all the answers

The rhoptries and micronemes are expelled into the host cytoplasm during the invasion process.

<p>True (A)</p> Signup and view all the answers

The __________ network of microtubules is involved in the motility of the Plasmodium parasite.

<p>subpellicular</p> Signup and view all the answers

What is the process by which sporozoites reproduce in liver cells?

<p>Exoerythrocytic schizogony (A)</p> Signup and view all the answers

Hypnozoites are only formed in P. malariae and P. vivax.

<p>False (B)</p> Signup and view all the answers

What causes the cyclic pattern of fever and chills known as malarial paroxysms?

<p>Release of pyrogens in response to merozoites.</p> Signup and view all the answers

The ___________________ stage occurs when the hypnozoites are reactivated, leading to a recurrence of disease symptoms.

<p>relapse</p> Signup and view all the answers

Match the following malaria stages with their characteristics:

<p>Sporozoites = Injected by mosquitoes into the human host Merozoites = Infect red blood cells Gametocytes = Differentiated forms in the blood that are taken up by mosquitoes Ookinetes = Develop into oocysts in mosquito gut</p> Signup and view all the answers

Which of the following symptoms is NOT associated with malaria?

<p>Coughing (D)</p> Signup and view all the answers

Merozoites are present in the blood for an extended period before infecting red blood cells.

<p>False (B)</p> Signup and view all the answers

What type of macrophages are Kupffer cells?

<p>CD68 positive macrophages</p> Signup and view all the answers

The __________________ phase begins when microgametes and macrogametes fuse in the mosquito.

<p>sexual</p> Signup and view all the answers

What enhances the attraction of Anopheles mosquitoes to infected hosts?

<p>HMBPP release (D)</p> Signup and view all the answers

What is one of the consequences of renal failure caused by infected RBCs?

<p>Oliguria or anuria (C)</p> Signup and view all the answers

Premunition indicates that a pre-existing infection can protect against newly arriving conspecifics.

<p>True (A)</p> Signup and view all the answers

What is the role of heme in the action of chloroquine against malaria parasites?

<p>Chloroquine prevents the conversion of heme into hemozoin, leading to toxic buildup of heme that destroys the parasite.</p> Signup and view all the answers

As kidney function declines, urine output is reduced, leading to ______ or sometimes anuria.

<p>oliguria</p> Signup and view all the answers

Match the following terms related to malaria to their definitions:

<p>Chloroquine = First antimalarial drug that targets asexual phase Primaquine = Drug targeting hypnozoites G6PD deficiency = Increases likelihood of RBC rupture under oxidative stress Thalassemia = Erythrocytes unfavorable for Pf development</p> Signup and view all the answers

Which of the following describes a method to reduce malaria transmission?

<p>Introducing mosquito-eating fish in ponds (D)</p> Signup and view all the answers

Older individuals are more likely to exhibit high parasitemia.

<p>False (B)</p> Signup and view all the answers

What mutation allows malaria parasites to develop resistance to chloroquine?

<p>Mutation of the PfCRT protein</p> Signup and view all the answers

Hemoglobin released from destructed RBCs appears in the urine, as kidneys cannot filter urine, leading to ______.

<p>black water fever</p> Signup and view all the answers

What is the main action of artemisinin in the treatment of malaria?

<p>Acts on the asexual phase of the parasite (B)</p> Signup and view all the answers

What is the typical duration of the hot stage in malaria symptoms?

<p>2-6 hours (C)</p> Signup and view all the answers

TNF-alpha is considered an anti-inflammatory cytokine.

<p>False (B)</p> Signup and view all the answers

What are the symptoms of severe malaria?

<p>Respiratory distress, anemia, hypoglycemia, metabolic acidosis, renal failure, coma</p> Signup and view all the answers

Malarial paroxysm cycles for Vivax and Ovale occur every ____ hours.

<p>48</p> Signup and view all the answers

Match the following complications of malaria with their descriptions:

<p>Cerebral malaria = Reduced consciousness and coma Severe malarial anemia = Destruction of erythrocytes Metabolic acidosis = Accumulation of waste due to blockage Rosetting = Infected RBCs binding to uninfected RBCs</p> Signup and view all the answers

Which species of malaria is considered the most pathogenic?

<p>Plasmodium falciparum (C)</p> Signup and view all the answers

PfEMP1 proteins allow infected red blood cells to bind to endothelial walls.

<p>True (A)</p> Signup and view all the answers

What do merozoites produce to evade the host's immune response?

<p>PfEMP1 proteins</p> Signup and view all the answers

The enzyme ______ neutralizes toxic heme into harmless hemozoin crystals during the digestion of hemoglobin.

<p>plasmepsin</p> Signup and view all the answers

Which process leads to the increased metabolic demand of infected erythrocytes?

<p>High metabolic demand of the parasite (D)</p> Signup and view all the answers

Rosetting refers to the binding of infected RBCs to each other.

<p>True (A)</p> Signup and view all the answers

What is the role of PTEX in Plasmodium-infected erythrocytes?

<p>PTEX allows the parasite to expel its proteins into the RBC cytoplasm.</p> Signup and view all the answers

The cycle of malaria infection typically manifests every ____ hours for the malaria species Plasmodium malariae.

<p>72</p> Signup and view all the answers

Which of the following processes describes the destruction of erythrocytes leading to jaundice in severe malaria?

<p>Hemolysis (A)</p> Signup and view all the answers

Flashcards

Apicomplexa

A phylum of parasitic protozoa known for their complex life cycles and ability to invade host cells. They include important human pathogens like Plasmodium (malaria) and Toxoplasma.

Apicoplast

A remnant of a chloroplast found in some apicomplexan parasites. It's essential for their survival, potentially involved in host cell invasion and nutrient synthesis.

Apical Complex

A specialized structure composed of five organelles at the anterior end of apicomplexan parasites, used for attaching to and invading host cells.

Sporogony

The sexual stage of the apicomplexan life cycle, occurring in the mosquito host. It involves the production of sporozoites, which are infectious to humans.

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Merogony

The asexual stage of the apicomplexan life cycle, occurring in the human host. It involves the multiplication of parasites within red blood cells.

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Gametogony

The stage in the apicomplexan life cycle where male and female gametes (sex cells) are produced. Occurs within the mosquito.

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Host Cell Invasion

The process by which apicomplexan parasites enter host cells. The apical complex plays a key role, using specific proteins to attach and penetrate the cell membrane.

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Plasmodium Species

The genus of apicomplexan parasites that cause malaria. Different species have different characteristics and cause varying degrees of disease severity.

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Sporozoite

The initial stage of the malaria parasite that is injected by an infected mosquito into a human host.

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Kupffer Cells

Specialized macrophages found in the liver that filter blood and can get infected by sporozoites.

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Hepatocyte

A liver cell that gets infected by sporozoites after they pass through Kupffer cells.

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Exoerythrocytic Schizogony

Asexual reproduction of the malaria parasite within a liver cell where the parasite replicates and divides without cytoplasmic division.

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Merozoite

The product of exoerythrocytic schizogony – a parasite cell that is released from the liver and infects red blood cells.

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Hypnozoite

A dormant stage of the Plasmodium vivax and Plasmodium ovale parasites that remains in the liver and can reactivate later, causing relapse.

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Relapse

The recurrence of malaria symptoms due to the reactivation of hypnozoites in the liver.

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Recrudescence

The recurrence of malaria symptoms due to ineffective immune response or inadequate drug treatment.

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Ring Stage

The early stage of the malaria parasite within a red blood cell, characterized by a ring-shaped appearance.

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Sequestration

The process where infected red blood cells containing Plasmodium falciparum parasites adhere to the lining of blood vessels, especially in the brain, causing blockage and severe complications.

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NO and Brain

Nitric Oxide (NO) causes vasodilation in the brain, which can lead to intracranial hypertension (increased pressure in the skull). This can interfere with normal neurotransmission, causing symptoms like psychosis and coma.

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Malaria and Kidney Failure

Malaria-infected red blood cells (RBCs) accumulate in the small blood vessels of the kidneys, obstructing blood flow. This blockage causes acute tubular necrosis, damaging kidney tubules and impairing kidney function, leading to renal failure.

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Black Water Fever

In severe malaria, damaged red blood cells release hemoglobin into the urine, giving it a dark, almost black color. This is called black water fever.

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Malaria Immunity

People living in malaria-endemic regions often develop immunity to severe infections. This immunity is slow to develop and short-lived, meaning it fades if they move to a malaria-free area or stop getting infected.

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Premunition

A pre-existing malaria infection offers protection against new malaria infections, preventing serious disease symptoms. This is called premunition.

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Malaria and Age

Older individuals in malaria-endemic areas are less likely to have high levels of parasites in their blood (parasitemia) and experience severe complications.

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Sickle Cell Anemia and Malaria

People with sickle cell anemia, even if they only carry one sickle cell allele, have a resistance to malaria. Sickle-shaped red blood cells are less suitable for parasite replication.

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Ovalocytosis and Malaria

Oval-shaped red blood cells are resistant to malaria parasites. These cells are harder for the parasite to invade.

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Duffy-Negative and Malaria

People who are Duffy-negative are resistant to Plasmodium vivax, a type of malaria parasite. They lack the Duffy antigen, which the parasite uses to enter red blood cells.

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Thalassemia and Malaria

People with thalassemia, a blood disorder affecting hemoglobin production, are less susceptible to malaria. Their red blood cells are unfavorable for parasite development.

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Malarial Paroxysm Cycle

The cyclical pattern of symptoms in malaria, including the hot stage, sweating stage, and recovery phase, recurring every 48 hours for vivax and ovale, and every 72 hours for malaria.

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TNF-alpha

A cytokine produced by the host's immune system that contributes to fever and inflammation in malaria. It is also a pyrogen, meaning it causes fever.

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Pyrogen

A substance that causes fever, such as TNF-alpha, produced by the host's immune system.

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Endogenous Pyrogen

A pyrogen produced by the host's own body, unlike exogenous pyrogens which come from external sources.

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PfEMP1 Protein

A protein found on the surface of infected red blood cells (RBCs) that allows them to bind to endothelial walls and avoid destruction by the spleen.

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Rosetting

When infected red blood cells bind to uninfected red blood cells, forming clusters and enhancing parasite survival.

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Antigenic Variation

The ability of Plasmodium parasites to change their surface antigens, allowing them to evade the host's immune system.

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Parasitophorous Vacuole (PV)

A membrane-bound compartment within an infected red blood cell where the parasite resides and grows.

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Knobs

Protrusions on the surface of infected red blood cells caused by the parasite's PfEMP1 proteins, which aid in adhesion to blood vessel walls and sequestration.

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Maurer's Clefts

Structures within infected red blood cells that facilitate the movement of parasite proteins.

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PTEX

A protein transporter in the parasite that allows it to expel its own proteins into the cytoplasm of the host red blood cell.

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Cerebral Malaria

A severe complication of malaria caused by the parasite P. falciparum, where infected red blood cells block blood flow to the brain, leading to coma, seizures, and other neurological problems.

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Severe Malarial Anemia

A severe complication of malaria, characterized by a decrease in red blood cells, due to the destruction of infected red blood cells by the parasite.

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Study Notes

Plasmodium and Malaria

  • Phylum Apicomplexa: Includes Plasmodium, Cryptosporidium, Toxoplasma, Babesia, among others. Majority are obligate intracellular parasites, except Cryptosporidium.
  • Likely evolved from predatory flagellates/dinoflagellates. Retained apicoplast (chloroplast remnant) acquired by secondary endosymbiosis.
  • Apicoplast is crucial for parasite survival; involved in host cell invasion and nutrient synthesis.
  • Apical complex (apical organelles): used for attachment and invasion of host cells.
  • Apical complex structure: Polar ring (unknown function), Conoid (spiral microtubules), Rhoptries (secretory, anterior), Micronemes (small, connect to rhoptries), Subpellicular microtubule network.
  • Rhoptries and micronemes are involved in host RBC invasion; other organelles' functions less well understood.
  • Plasmodium life cycle: Sporogony, Merogony, Gametogony.

Plasmodium Life Cycle

  • Sporogony (in mosquito): Development of sporozoites in mosquito's gut.
  • Merogony (in liver and red blood cells): Asexual reproduction involving schizonts (multinucleated cells). Formation of merozoites (infectious forms).
  • Gametogony (in red blood cells): Some merozoites differentiate into sexual forms: microgametes (flagellated) and macrogametes (larger).

Host Cell Invasion Mechanism

  • Apical end attaches to host cell; rhoptries, micronemes, and dense granules are expelled into host cytoplasm.
  • Micronemal adhesins (TRAP, EGF-like, APPLE domains, lectin) facilitate attachment. Examples: Plasmodium vivax - Duffy binding protein, Plasmodium falciparum - erythrocyte binding antigen (EBA).
  • Subpellicular microtubule network involved in parasite motility, active invasion.
  • Parasitophorous vacuole (PVM) encapsulates parasite, derived from parasite and host cell membrane. PVM ruptures before merozoite release.

Human Malaria

  • Caused by 6 Plasmodium species infecting humans: P. falciparum, P. vivax, P. malariae, P. ovale curtisi, P. wallikeri, P. knowlesi.
  • Four main stages of the Plasmodium life cycle in humans:
    • Liver stage: Sporozoites enter liver cells (hepatocytes), undergo asexual reproduction (exoerythrocytic schizogony). Merozoites enter bloodstream.
    • Blood stage: Merozoites infect red blood cells (RBCs); develop into ring stages and trophozoites, ingest Hb. Produces hemozoin. Asexual reproduction (schizogony) until merozoites release into blood, inducing paroxysms
    • Sexual stage: Some merozoites differentiate into gametocytes (micro and macro). Travel in blood until consumed by mosquito.
    • Sporogony (in mosquito): Zygotes develop into ookinetes, penetrate mosquito gut wall to form oocysts. Sporozoites develop and migrate to the mosquito's salivary glands.
  • Vector transmission: Anopheles mosquitoes. Infected hosts attract anopheles by releasing HMBPP and increased CO2, aldehydes and monoterpenes from erythrocytes.
  • Hypnozoite stage: Dormant forms in liver (P. vivax, P. ovale); can cause relapses.
  • Recrudescence: Recurrence of disease in an existing infection due to immune inadequacy or suboptimal drug treatment.
  • Clinical manifestations: Flu-like symptoms, fever, muscle pain, anorexia, nausea, malarial paroxysms (chills, fever, sweats). Severe cases include anemia, respiratory stress, hypoglycemia, renal failure, and coma.

Plasmodium falciparum: Pathogenesis

  • Invades all RBC stages, particularly reticulocytes.
  • Sequestration of infected RBCs (to blood vessel walls) limits immune system response.
  • Produces PfEMP1 proteins with variable (antigenic variation) structures binding diverse host receptors, enabling sequestration and rosetting of red blood cells.
  • Knob formation (PfEMP1) on infected RBC surface for enhanced cytoadherence to blood vessels. This can lead to severe disease like cerebral malaria.

Plasmodium Pathogenesis: Mechanisms

  • Severe malarial anemia: Destruction of erythrocytes, bilirubin formation, jaundice, hemozoin accumulation, impaired immunity, decreased iron recycling.
  • Host inflammatory response: Sequestration causes impaired blood flow, resulting in hypoperfusion, ischemia, and hypoxia in organs like the brain. Cytokines (e.g., TNF-α) contribute to fever and pathogenesis.
  • Renal failure: Infected RBCs can block kidney capillaries, leading to acute tubular necrosis. Released Hb appears in urine (blackwater fever).

Immunity and Resistance

  • Limited long-term immunity in endemic regions.
  • Immune responses are slow to develop. Factors like sickle-cell anemia, ovalocytosis, Duffy-negative status, thalassemia, and G6PD deficiency can confer resistance.

Drug Resistance

  • Chloroquine acts by preventing heme detoxification; resistance arises in the PfCRT protein, which pumps chloroquine out.
  • Antimalarial drug targets include asexual parasites (chloroquine), hypnozoites (primaquine/tafenoquine), and gametocytes (gametocides).

Epidemiology and Control

  • Malaria transmission depends on human and animal reservoirs, vectors (Anopheles species), new host populations, and environmental factors.
  • Control strategies include vector control, mosquito nets, and antimalarial drugs. Mosquito control and vaccine development (Mosquirix) are also crucial.

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Explore the fascinating world of Plasmodium, the parasite responsible for malaria. This quiz covers its life cycle, evolutionary background, and unique structures that facilitate host invasion. Test your knowledge on the biology and ecology of this important organism.

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