¹⁸ Further information is provided in Annex 9.12

Patients with high parasite counts are known to be at increased risk of dying, although the relationship between parasite counts and prognosis varies at different levels of malaria endemicity. Many hyperparasitaemic patients have evidence of vital organ dysfunction but there is a large subgroup in which no other manifestations of severe disease are present. These patients have symptoms and signs compatible with a diagnosis of uncomplicated malaria in association with a high parasite count (sometimes termed uncomplicated hyperparasitaemia). The relevance for treatment is firstly the increased risk of progressing to severe malaria, and secondly the generally higher treatment failure rates. This is of particular concern as resistance to antimalarials is most likely to arise in patients with heavy parasite burdens and little or no immunity. In a low-transmission area in north-west Thailand, the overall mortality of uncomplicated falciparum malaria was 0.1%, but in patients with parasitaemia of >4% it was 3%. In areas of moderate or high transmission, much higher parasitaemias are often well tolerated, however. There is not enough evidence to provide a firm recommendation on the definition of hyperparasitaemia, although ≥5% parasitaemia in a low-transmission setting and ≥10% in a higher transmission setting are commonly used.

8.13.1 Treatment of hyperparasitaemia

Available evidence indicates that use of oral treatment under close supervision is effective in the treatment of patients with hyperparasitaemia who have no other features of severe malaria. Parenteral treatment should, however, be substituted at any time if there is concern. The rapidity of action of the artemisinin derivatives makes them ideal drugs. The standard treatment course should be given, as there is insufficient information on the safety of higher doses of the partner drug. Alternatively, the first dose of artemisinin derivative can be given parenterally or rectally to ensure adequate absorption, followed by a full course of ACT. Mefloquine-containing regimens in which the tablets are dispensed separately should be given such that mefloquine is given on days 2 and 3, rather than day 1, when it is better tolerated, with a lower incidence of early vomiting.

The optimum duration of treatment for hyperparasitaemia is still unresolved. Data to support the suggestion that patients should be treated conservatively with 7 days of an artemisinin derivative, plus a full course of partner medicine (e.g. artesunate 7 days + mefloquine 25 mg/kg bw divided over 2 days) are lacking. A longer ACT course than is recommended for uncomplicated malaria may not be possible in places where only fixed-dose combinations are available.

Summary of recommendations on the treatment of hyperparasitaemia in falciparum malaria