MALARIA – 

INTRODUCTION

• Malaria is a life-threatening infectious disease caused by protozoa of the genus Plasmodium.
• It is transmitted to humans through the bite of an infected female Anopheles mosquito.
• It is a major tropical disease, especially in developing countries.
• Fever in a patient returning from an endemic area should always raise suspicion of malaria.

ETIOLOGY

Five species infect humans:

1.     Plasmodium falciparum

• Most severe form
• Common in Africa
• Incubation: 7–30 days
• No relapse (no dormant liver stage)

2.     Plasmodium vivax

• Common in Asia & Latin America
• Incubation: ~2 weeks
• Has dormant liver stage (hypnozoites) → relapse

3.     Plasmodium ovale

• Found in West Africa
• Similar to P. vivax (relapsing type)

4.     Plasmodium malariae

• Worldwide distribution
• Incubation: ~18 days
• Causes chronic low-grade infection

5.     Plasmodium knowlesi

• Zoonotic (from monkeys)
• Seen in Southeast Asia
• Rapid and potentially fatal

LIFE CYCLE

Malaria involves two hosts:

• Human (asexual cycle)
• Mosquito (sexual cycle)

1. Sporogonic Cycle (Mosquito)

• Gametocytes → fertilization → zygote
• Zygote → ookinete → oocyst
• Oocyst ruptures → sporozoites → migrate to salivary glands

2. Exo-erythrocytic Cycle (Liver Stage)

• Sporozoites enter liver → form schizonts
• Schizonts release merozoites into blood
• P. vivax & P. ovale form hypnozoites → relapse

3. Erythrocytic Cycle (Blood Stage)

• Merozoites infect RBCs
• Stages:
• Ring form (trophozoite)
• Schizont
• RBC rupture → release of merozoites
• Causes fever and symptoms

Fever periodicity:

• 48 hrs → P. falciparum, vivax, ovale
• 72 hrs → P. malariae
• 24 hrs → P. knowlesi

PATHOPHYSIOLOGY

• RBC destruction → anaemia
• Hemoglobin release → jaundice
• Capillary blockage (esp. falciparum) → organ damage

CLINICAL MANIFESTATIONS

Common Symptoms

• Fever with chills and sweating
• Headache
• Malaise and fatigue
• Nausea, vomiting, diarrhea
• Myalgia and arthralgia

Signs

• Pallor (anaemia)
• Splenomegaly
• Jaundice

SEVERE MALARIA (Medical Emergency)

Commonly due to P. falciparum

• Cerebral malaria (coma, seizures)
• Severe anaemia
• Hypoglycaemia
• Metabolic acidosis
• Acute kidney injury
• ARDS (respiratory distress)
• Shock (hypotension)
• DIC (bleeding disorders)

BLACKWATER FEVER

• Severe complication
• Features:
• Dark/red urine
• Massive hemolysis
• Due to hemoglobinuria

DIAGNOSIS

• Peripheral blood smear (gold standard)
• Rapid antigen tests
• PCR (confirmatory)
• Lab findings:
• Low platelets
• Increased bilirubin
• Anaemia

PREVENTION

• Mosquito control:
• Eliminate stagnant water
• Insecticide spraying
• Personal protection:
• Mosquito nets
• Repellents
• Chemoprophylaxis (travelers)
• Health education

TREATMENT

Antimalarial Drugs

• Chloroquine
• Artemisinin-based combination therapy (ACT)
• Mefloquine
• Primaquine (for relapse prevention)

Combination Therapy

• Artemisinin + lumefantrine
• Atovaquone + proguanil

In Pregnancy

• Quinine + clindamycin
• Artemisinin derivatives (in later stages)

IMPORTANT EXAM POINTS

• Vector: Female Anopheles mosquito
• Infective stage: Sporozoite
• Diagnostic stage: Blood smear
• Relapse: P. vivax & P. ovale
• Severe malaria: P. falciparum