Malaria: Overview and Key Concepts

Introduction

• Malaria is a serious parasitic infection caused by Plasmodium species.
• Transmitted by the Anopheles mosquito.
• Affects young children, pregnant women, immunocompromised individuals, and travelers.
• Global health issue, prevalent in South America, Africa, South Asia, and Southeast Asia.

Plasmodium Species

• Five species cause diseases in humans:
  • Plasmodium falciparum
  • Plasmodium vivax
  • Plasmodium ovale
  • Plasmodium malariae
  • Plasmodium nalesi (transmitted by infected monkeys, not mosquito)

Infection Process

1. Transmission

   • By female Anopheles mosquito in search of a blood meal.
   • Attracted by exhaled CO2 and foot odor.
   • Sporozoites in mosquito's salivary gland enter the bloodstream.

2. Liver Stage (Exoerythrocytic Phase)

   • Sporozoites invade liver (hepatocytes) and undergo asexual reproduction (schizogony).
   • Matures into merozoites within 1-2 weeks.
   • Hypnozoites in P. vivax and P. ovale may stay dormant (latent infection).

3. Blood Stage (Erythrocytic Phase)

   • Merozoites invade red blood cells (RBCs).
   • Stages:
     • Early trophozoite (ring form)
     • Late trophozoite
     • Schizont
   • Some merozoites develop into gametocytes for sexual reproduction.

Clinical Symptoms

• Major symptom: Fever with chills and rigors.
• Others: splenomegaly, anemia (especially in P. falciparum).
• Fever timing varies by species:
  • P. malariae: every 72 hours
  • P. vivax, P. ovale, P. falciparum: every 48 hours
  • P. nalesi: every 24 hours
• Complicated malaria: cerebral malaria, acute respiratory distress, acute renal failure, severe anemia.

Diagnosis

1. Microscopy (gold standard)

   • Thin and thick blood smears.
   • Identifies parasites in RBCs; species identification based on morphology.
   • Requires experienced personnel.

2. Antigen Detection

   • Looks for parasite-derived products (e.g., parasitic lactate dehydrogenase).
   • Uses dipstick methods, field applicable but less sensitive.

Treatment

• Based on infection stage, species, severity, age, and resistance.
• Prophylactic treatment for non-infected individuals.
• Radical treatment targets hypnozoites.

Prevention

1. Preventing Man-Vector Contact

   • Insecticide-treated bed nets, full-body clothing, mosquito repellents.

2. Reducing Vector Density

   • Destroying breeding sites, insecticide sprays.

3. Reducing Parasite Population

   • Early detection and treatment.