WEEK 7-Lec 1.3

MED3ATB 2021 Eucaryotic Parasites Part 3: Malaria - Mick Foley

Page 1

• Title: Eucaryotic Parasites Part 3 (Malaria: a detailed example)

Page 3: The Individual Burden of Malaria

• Excessive Energy Requirement

• Anaemia

• Iron Deficiency

• Obstruction of Circulation

Page 4: The Global Burden of Malaria

• Exposure and Infection Rates

  • 2-3 billion people exposed across tropical areas worldwide

  • Over 500 million infected annually

  • More than 2 million deaths each year

• At-Risk Populations

  • Pregnant women and children are at greatest risk

• Leading Cause of Childhood Death

  • Plasmodium falciparum is a significant contributor

• Challenges

  • No effective vaccine available

  • Drug resistance is a growing problem

Page 5: Life Cycle of Malaria Parasite

• Stages of Development

  • Sporozoites

  • Liver stage

  • Ookinete

  • Red Blood Cells (RBC)

  • Zygote

  • Merozoites

  • Gamete formation in mosquito gut

Page 6: Types of Plasmodium Species

• Human-Infecting Species

  • P. falciparum

  • P. vivax

  • P. ovale

  • P. malariae

  • P. knowlesi (Monkey malaria)

Page 7: Symptoms of Malaria

• Common Symptoms

  • Headache

  • Periodic fever (48h for P. malariae, 72h for P. vivax)

• Stages of Fever

  • Cold stage: chills and shivering

  • Hot stage: high fever (up to 41°C), enlarged spleen and liver, anemia

  • Sweating stage: resolution of fever

Page 8: Pathogenesis of Malaria

• Mechanisms of Disease

  • Antigenic variation (PFEMP1)

  • Cytoadhesion to blood vessels

  • Evasion of spleen destruction

  • Pregnancy-associated pathogenesis affecting multiple organs (cerebral, kidney, lungs)

Page 9: Host Defense Mechanisms

• Red Blood Cell Adaptations

  • Deformation of RBCs aids in oxygen delivery

  • Malaria parasites invade and grow within RBCs

  • Human adaptations to combat malaria include sickle cell anemia, which makes RBCs inhospitable to the parasite

Page 10: Sickle Cell Anemia

• Sickle Cell Anemia is a genetic blood disorder characterized by the presence of abnormal hemoglobin, which causes red blood cells to become rigid, sticky, and shaped like crescent moons (or sickles). This abnormal shape can lead to blockages in blood vessels, pain, and various complications. Although sickle cells are resistant to malaria, individuals with the disorder may suffer from severe health issues due to the sickling of their blood cells.

• Resistance to Malaria

  • Sickle cells are resistant to malaria but have drawbacks

  • Abnormal hemoglobin mutation leads to fragile and stiff cells

  • Individuals with one sickle cell gene experience mild disease; those with two have severe disease

Page 11: Types of Innate Resistance

• Hemoglobin Abnormalities

  • Sickle-cell

  • Thalassemias

  • HbC and HbE erythroids

• Other Erythrocyte Mutations

  • Glucose-6-phosphate dehydrogenase deficiency

  • PK deficiency

  • Elliptocytosis

  • Southeast Asian ovalocytosis

  • Duffy antigen receptor negativity

  • Gerbich antigen receptor negativity

  • Other rare mutations

Page 12: Geographic Distribution of Malaria and Disorders

• High Malaria Risk Areas

  • Red indicates areas with high malaria risk

  • Hatched areas show distribution of red blood cell disorders

Page 13: Host Defense Mechanisms Against Parasites

• Genetic Factors

  • Evolutionary loss of important host factors

  • Host alterations affecting parasite survival

• Immune Responses

  • Unspecific: Phagocytosis (Leucocytes), gastric acids

  • Specific: Humoral (antibodies, complement system), cellular (T-cells, macrophages)

Page 14: Mechanisms of Immune Evasion

• Strategies Used by Parasites

  • Antigenic variation

  • Encapsulation

  • Retreat into vital tissues

  • Absorption of antibodies

  • Molecular masking

  • Immune suppression/modulation

  • Immune decoys

Page 15: Intervention Strategies

• Preventive Measures

  • Avoid contact with contaminated water

  • Avoid fecal/urine exposure

  • Target free-living stages (miracidia, cercaria, eggs)

  • Vector control (molluskicides, predators like carp/ducks)

  • Treat/remove host reservoirs (e.g., cows)

• Host resistance refers to the ability of an organism's body, like a human or animal, to defend itself against infections, including those caused by parasites like malaria. This can involve various mechanisms like genetic factors, immune responses, and adaptations that help to protect the host from becoming ill.

Page 16: Factors Influencing Disease

• Key Influencing Factors

  • Parasite pathogenesis

  • Host resistance and genetics

  • Environmental factors (habitat, temperature, behavior)

  • Population density

This note summarizes the key points from the transcript on malaria, covering its burden, symptoms, host defenses, and intervention strategies

Life Cycle of Malaria Parasite

Stages of Development:

1. Sporozoites - The infective stage injected into humans by mosquito bites.

2. Liver Stage - Sporozoites travel to the liver, where they develop and multiply.

3. Ookinete - Formed in the mosquito's gut after feeding on infected blood.

4. Red Blood Cells (RBC) - Merozoites released from the liver invade RBCs.

5. Zygote - Result of gamete fusion, develops in the mosquito's gut.

6. Merozoites - Released back into the bloodstream to infect more RBCs.

7. Gamete Formation - Last stage occurs in the mosquito gut to continue the lifecycle.

malaria is caused by parasites from the genus Plasmodium. These parasites are transmitted to humans primarily through the bites of infected female Anopheles mosquitoes.