Plasmodium vivax
P.vivax is selective in that it invades only young immature erythrocytes. Infections of P. vivax have the following characteristics:
• Infected red blood cells are usually enlarged and contain numerous pink granules or schuffner’s dots.
• The trophozoite is ring-shaped but amoeboid in appearance.
• More mature trophozoites and erythrocytic schizonts containing up to 24 merozoites are present.
• The gametocytes are round
Epidemiology
P. Vivax is the most prevalent of the human plasmodia with the widest geographic distribution, including the tropics, subtropics, and temperate regions. However, it is the second most prevalent in Ethiopia following P. falciparum.
Clinical Features
After an incubation period (usually 10 to 17 days), the patient experiences vague flu-like symptoms, such as headache, muscle pains, photophobia, anorexia, nausea and vomiting. As the infection progresses, increased numbers of rupturing erythrocytes liberate merozoites as well as toxic cellular debris and hemoglobin in to circulation. In combination, these substances produce the typical pattern chills, fever and malarial rigors. These paroxysms usually reappear periodically (generally every 48 hours) as the cycle of infection, replication, and cell lyses progresses. The paroxysms may remain relatively mild or may progress to severe attacks, with hours of sweating, chills, shaking persistently, high temperatures (1030F to 1060F) and exhaustion. Since P.vivax infects only the reticulocytes, the parasitemia is usually limited to around 2 to 5% of the available RBCs.
INSTAGRAM
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