Introduction

Presentation can be vague, any or all of wide variety of symptoms.
Always should be considered in unwell patients returning from or having passed though endemic areas

Organism

Parasite is a plasmodium (protozoan). 4 species infect humans:

  • P.falciparum (80% cases worldwide, highest mortality)
  • P.vivax
  • P.ovale
  • P.malariae

 

Transmission

By the bite of the female anopheline mosquito
(can also be aquired transplacentaly, by transfusion or inoculation.)

Life Cycle of parasite

Epidemiology

  • Very important tropical disease – occurs throughout tropics and subtropics at altitudes below 1500m
  • 0.5-2 million deaths per year (mostly <5yrs)

Protective factors

Red blood cells genetic factors

  • Sickle cell trait (HbS) is relatively protected against P. falciparum malaria (àbiologic advantage)
  • Duffy blood group negative red blood cells are resistant to infection by P. vivax.

Acquired immunity can develop after repeated attacks. A person can still be infected by malaria parasites but may not develop severe disease. (this is usually lost In pregnancy).

Pathogenesis

  • Haemolysis of RBCs and adherence of infected RBCs to capillaries and cytokine release.
  • In falciparum, RBCs containing schizonts adhere to capillary epithelium in the brain, kidney, liver lungs and gut vessels become congested
  • Organs anoxic.
  • Rupture of schizonts liberate toxic and antigenic substances that may cause further damage

Diagnosis

Thick and thin blood films. Look for trophozoites and % RBC infected. High % (>30%) has high mortality

Treatment

Quinine in mainstay of treatment (IV if >2% RBC infected)
Resistance of p.falciparum to chloroquine in widespread)
Supportive measures in severe disease.

Prevention

  • Mosquito nets and well covering clothing
  • Insect repellant and indoor spraying (ie DDT)
  • Prophylaxis medications
    •  Doxycycline (cheapest, taken daily for 2 weeks prior to visiting and 4 weeks after returning from endemic area, SE include sunlight hypersensitivity, nausea and diarrhea).
    • Malarone (most expensive, taken daily for 2 days before and 7 days after trip, fewer side effects)
    • Larium (combination medication, taken weekly for 2 weeks prior to visiting and 4 weeks after returning from endemic area contraindicated in those with history of epilepsy or psychiatric disorders due to neuropsychiatric side-effects such as anxiety and hallucinations)

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