Uncomplicated Malaria - Short Note (MBBS Pediatrics)

Definition

Etiology and Epidemiology

• Vector: Female Anopheles mosquito (bites at dusk/night)
• In endemic areas, malaria primarily affects children; adults develop immunity with repeated exposure
• In highly endemic areas, a large proportion of children carry asymptomatic parasitemia; illness is commonly mild but occasionally severe

Life Cycle

1. Mosquito bite - sporozoites injected into bloodstream
2. Pre-erythrocytic (liver) stage - sporozoites infect hepatocytes → tissue schizonts → merozoites released (P. vivax/ovale also form dormant hypnozoites*)
3. Erythrocytic stage - merozoites invade RBCs → ring stage → trophozoite → schizont → RBC rupture releases merozoites + pyrogens → FEVER
4. Sexual stage - some merozoites form gametocytes → ingested by mosquito → fertilization → oocyst → sporozoites migrate to salivary gland

Pathophysiology of Fever

• Tertian fever (every 48 h) - P. vivax, P. ovale, P. falciparum
• Quartan fever (every 72 h) - P. malariae

Clinical Features

Classic Malarial Paroxysm (three stages)

1. Cold stage - sudden onset rigors, chills, teeth chattering (lasts 15-60 min)
2. Hot stage - high fever (39-41°C), flushed, dry skin, headache, vomiting (lasts 2-6 h)
3. Sweating stage - profuse diaphoresis, temperature falls, patient exhausted (lasts 2-4 h)

Note: Classic paroxysms are often absent in P. falciparum or in patients who received partial chemoprophylaxis.

Other Features

• Prodrome: Malaise, myalgia, headache, anorexia (often mistaken for influenza or gastroenteritis)
• GI symptoms: Nausea, vomiting, abdominal pain common in children
• Splenomegaly: Common; progressive with repeated infections
• Hepatomegaly: Variable
• Anemia: Normocytic normochromic; due to RBC destruction + dyserythropoiesis
• Thrombocytopenia: Frequent but usually does not cause bleeding
• No lymphadenopathy, no rash (if present, consider alternative/co-existing diagnosis)

In Children Specifically

• Febrile seizures more common
• GI symptoms predominate (diarrhea, vomiting)
• Rapidly developing severe anemia more common than in adults
• High parasite density correlates with likelihood of true malaria disease (vs asymptomatic parasitemia)

Investigations

Confirmatory (Gold Standard)

• Thick smear: Detects and quantifies parasitemia (more sensitive)
• Thin smear: Species identification and morphology
• Key morphological features:

• Detects P. falciparum HRP-2 antigen (or LDH for non-falciparum)
• Quick (~15 min), no microscopy needed
• Cannot quantify parasitemia; false negatives in high parasitemia (hook effect with HRP-2 deletion mutants)

Supportive Investigations

WHO Criteria: Uncomplicated vs Complicated Malaria

• Prostration / inability to sit
• Altered consciousness / seizures
• Severe anemia (Hb <7 g/dL in children)
• Respiratory distress / pulmonary edema
• Hypoglycemia (<2.2 mmol/L)
• Hemoglobinuria / jaundice
• Abnormal bleeding / shock
• Parasitemia >5% or >200,000 parasites/μL

Treatment

1. P. falciparum (chloroquine-resistant areas - most of the world)

• Quinine 650 mg TDS × 7 days + Doxycycline 100 mg BD × 7 days (avoid doxycycline in children <8 yrs - use clindamycin instead)
• Atovaquone-Proguanil (Malarone) 4 tabs/day × 3 days

• 5-14 kg: 1 tab BD × 3 days
• 15-24 kg: 2 tabs BD × 3 days
• 25-34 kg: 3 tabs BD × 3 days

• 34 kg: 4 tabs BD × 3 days

2. P. vivax / P. ovale (chloroquine-sensitive areas)

• Chloroquine: 10 mg base/kg stat, then 5 mg base/kg at 6, 24, 48 h
• PLUS Primaquine (to eradicate hypnozoites and prevent relapse):
  • 0.25 mg base/kg/day × 14 days
  • Check G6PD status first - primaquine causes hemolysis in G6PD deficiency
  • Contraindicated in pregnancy and infants <6 months
• For chloroquine-resistant P. vivax (parts of SE Asia): Use ACT

3. P. malariae and P. knowlesi

• Chloroquine (as above); no primaquine needed (no hypnozoites)

Key Points for Exam

1. Most common cause of fever in tropics in children
2. Gold standard diagnosis = Peripheral blood smear (thick + thin)
3. Banana-shaped gametocytes = P. falciparum (pathognomonic)
4. Schuffner's dots = P. vivax and P. ovale
5. Relapse (due to hypnozoites) - P. vivax and P. ovale only; treat with primaquine after checking G6PD
6. ACT is first-line for P. falciparum uncomplicated malaria globally
7. Doxycycline is avoided in children <8 years - use clindamycin instead
8. Classic paroxysm (cold → hot → sweating) is often absent in P. falciparum
9. Thrombocytopenia + fever + travel history = think malaria
10. Do NOT use steroids in cerebral malaria (worsens outcomes)

Prognosis

• Uncomplicated P. falciparum malaria: mortality ~0.1% with prompt treatment
• Untreated or delayed P. falciparum: can progress to cerebral malaria (mortality 15-25%)
• Non-falciparum malaria: excellent prognosis with treatment