MALARIA=final

Plasmodium Malaria Parasite

Coccidia (Sporozoa)

  • Classification:

    • Coccidia are members of the class Sporozoa, within the Phylum Apicomplexa.

    • They possess an apical complex visible with an electron microscope.

  • Life Cycle Characteristics:

    • Features an alternation of generations: sexual (gametogony) and asexual (schizogony) reproduction.

    • Most members have alternative hosts.

  • Locomotion:

    • Movements include body flexion, gliding, or undulation of longitudinal ridges.

  • Plasmodium:

    • The genus Plasmodium serves as the prototype for this class and is responsible for malaria.

Malaria Overview

  • Major Species Infecting Humans:

    • Plasmodium falciparum

    • Plasmodium vivax

    • Plasmodium ovale

    • Plasmodium malariae

Etiology of Malaria

  • Major Species and Their Distribution:

    • P. vivax: Benign tertian malaria; accounts for 43% of cases.

    • P. falciparum: Malignant tertian malaria; accounts for 50% of cases.

    • P. malariae: Quartan malaria; accounts for approximately 7% of cases.

    • P. ovale: Mild tertian malaria; accounts for less than 1% of cases.

Public Health Impact

  • Demographic Vulnerability:

    • Major health problem in warm climates, particularly in developing countries.

    • Leading cause of disease and death among children under five, pregnant women, non-immune travelers, and immigrants.

  • Transmission:

    • Caused by the bite of an Anopheles mosquito.

What is Malaria?

  • Definition:

    • Malaria is caused by protozoan parasites of the genus Plasmodium.

  • Species Overview:

    • P. falciparum: Most critical, responsible for 50% of global cases and severe morbidity.

    • P. vivax: Most widespread geographically; causes 43% of malaria cases.

    • P. ovale: Rare; primarily in tropical Africa, also in South America and Asia.

    • P. malariae: Responsible for 7% of malaria cases; present mainly in sub-tropical regions.

Geographical Distribution of Malaria

  • Current Status:

    • Historically widespread, now concentrated mainly in Africa, Asia, and Latin America.

    • Approximately 40% of the global population at risk.

    • Endemic in 91 countries; limited transmission pockets in 8 countries.

  • Ecological Factors Affecting Transmission:

    • Key factors: Temperature and rainfall affecting mosquito breeding.

    • Optimal development conditions: 25-30°C; halted below 16°C.

    • Resistance and socio-economic factors contribute to increased malaria prevalence in sub-Saharan Africa.

Historical Context

  • Timeline of Important Discoveries:

    • 2000 years ago: Ancient Chinese medicine noted symptoms and treatments for malaria.

    • 1880: Laveran discovered plasmodia in blood, awarded Nobel Prize in 1907.

    • 1897: Ross identified Anopheles mosquitoes as malaria transmitters; awarded the first medical Nobel Prize in 1902.

Life Cycle of Malaria

  • Hosts:

    • Vertebrate Host: Humans (intermediate host), where the asexual reproduction (schizogony) occurs.

    • Invertebrate Host: Mosquito (definitive host), where sexual reproduction (gametogony) occurs.

  • Stages:

    • Sexual and asexual cycles alternate in hosts.

    • Formation of sporozoites occurs after male and female gamete union in the mosquito.

Detailed Life Cycle Phases

  • Human Cycle:

    • Stages in Humans:

      • Pre-erythrocytic schizogony: Sporozoites enter liver and multiply.

      • Erythrocytic schizogony: Merozoites invade red blood cells (RBCs).

      • Exo-erythrocytic schizogony: Some merozoites can re-invade liver cells, causing relapses.

  • Mosquito Cycle:

    • Sporogony: Occurs in the mosquito after it feeds on infected blood.

Clinical Features and Phases

  • Disease Symptoms:

    • P. falciparum: Shortest incubation (7-10 days), causes severe symptoms like cerebral malaria, nausea, vomiting.

    • P. vivax: Longer incubation (10-17 days); presents with flu-like symptoms followed by periodic fever.

Treatment Approaches

  • P. falciparum Treatment:

    • Due to chloroquine resistance, alternative treatments include mefloquine, quinine, and doxycycline.

  • P. vivax Treatment:

    • Chloroquine for treatment with primaquine to eliminate gametocytes and prevent relapse.

Laboratory Diagnosis

  • Diagnosis Method:

    • Microscopic examination of blood films (thick and thin) is essential for confirming malaria and identifying specific species.

  • Serological Procedures:

    • Primarily used for epidemiological surveys or blood donor screenings.

Prevention Strategies

  • Control Measures:

    • Effective chemoprophylaxis and prompt diagnosis/treatment.

    • Mosquito breeding control and insect bite protection through nets and repellents.

Summary of Plasmodium Species

  • P. falciparum: Trophozoites multiple in red blood cells, causing severe disease, seasonal epidemics.

  • P. vivax: Selective for young red blood cells; causes relapsing malaria.

  • P. malariae: Longest incubation; less common, with less intense symptoms.

  • P. ovale: Similar to P. vivax but fewer relapses and milder cases.