Vivax Malaria

Vivax malaria is infection by Plasmodium vivax, which forms dormant liver hypnozoites that cause relapse weeks to years after the primary attack. Infection requires the Duffy antigen on red cells, so it is rare in most of West and Central Africa but occurs in the Horn of Africa and parts of East Africa, in travellers and migrants.

• Prefers young red cells (reticulocytes), so parasite density is usually under 2 percent.
• Causes recurrent anaemia, splenic rupture and, uncommonly, severe disease.

Fever with chills at 48 hour intervals, headache, myalgia, nausea, splenomegaly; relapses with milder symptoms.

• Differential diagnosis: falciparum malaria, P. ovale infection, dengue, typhoid, influenza, brucellosis, visceral leishmaniasis, bacterial sepsis, hepatitis.
• Complications: relapse, splenic rupture, severe anaemia, thrombocytopenia, acute respiratory distress syndrome, cerebral involvement (rare), anaemia in pregnancy, low birth weight, haemolysis in G6PD deficient people given 8 aminoquinolines.

Microscopy and species specific tests.

• Thick and thin films showing enlarged infected red cells with Schuffner dots; rapid tests detecting pLDH or aldolase (pfHRP2 tests do not detect P. vivax); PCR for mixed infection.
• G6PD quantitative test before radical cure; haemoglobin, platelets, glucose, pregnancy test.

Cure the blood stage and eliminate hypnozoites.

• Supportive: antipyretics (paracetamol 15 mg/kg or 1 g every 6 hours), fluids, rest, nutrition, treat anaemia, nets, avoid sun, education on relapse.
• Pharmacological, blood stage: chloroquine 25 mg base/kg over 3 days (10 mg/kg on day 1, 10 mg/kg on day 2, 5 mg/kg on day 3), or artemether lumefantrine for 3 days in doses by weight (35 kg and over 4 tablets of 20 mg/120 mg at 0, 8, 24, 36, 48 and 60 hours), especially where chloroquine resistance exists. Radical cure: primaquine 0.25 to 0.5 mg/kg base daily (usually 15 mg for adults) for 14 days with food after normal G6PD testing; or tafenoquine 300 mg single dose for adults with G6PD activity of 70 percent or more of normal. Mild to intermediate G6PD deficiency: primaquine 0.75 mg/kg base once weekly for 8 weeks under supervision; severe deficiency, no 8 aminoquinoline. Severe vivax malaria: IV artesunate 2.4 mg/kg at 0, 12 and 24 hours then once daily.
• Procedures: none; splenectomy only for rupture.
• Special groups: pregnancy and breastfeeding, chloroquine 10 mg/kg then 5 mg/kg (or 25 mg/kg total over 3 days) followed by weekly chloroquine 300 mg base until delivery; primaquine and tafenoquine contraindicated (give primaquine after delivery if normal G6PD); infants under 6 months, no primaquine; children, weight based primaquine.
• Red flags: haemoglobinuria after primaquine, severe anaemia, abdominal pain with shock (splenic rupture), recurrence within 28 days, breathing difficulty.
• Follow-up: repeat film at day 3 and day 28; haemoglobin at day 7 of primaquine; advise return for fever for 12 months; relapse requires a repeat course.