12.1. Use of gametocytocidal drugs to reduce transmission
Two antimalarial medicines have an effect specifically on gametocytes: primaquine and artemisinins. This can be of particular benefit in epidemic control and in programmes aiming for malaria elimination.
Primaquine selectively kills gametocytes. Especially in South-East Asia and South America, before the use of ACTs for the treatment of P. falciparum malaria, a single oral dose of 0.75 mg base/kg body weight primaquine (45 mg base maximal for adults) was added to a fully effective blood schizontocide to eliminate gametocytes and thus reduce transmission. Studies on the impact of this strategy are very limited. Where it has been used, the single dose of primaquine was well tolerated, and prior testing for G6PD deficiency was not required. There is no experience with its use in Africa, where there is the highest prevalence of G6PD deficiency in the world.
ACTs reduce gametocyte carriage. One randomized comparison of ACTs and primaquine has reported a greater effect for ACT than primaquine on gametocyte carriage. A more recent study compared the added value of primaquine to AS+SP combination in the treatment of falciparum malaria in United Republic of Tanzania. It reported that primaquine clears gametocytes that persist after treatment with AS+SP, including those at a submicroscopic level: this demonstrates an added benefit of combining a single dose of primaquine with an ACT16. The addition of a single dose of primaquine to ACT treatment is, therefore, recommended in programmes aimed at reducing transmission, provided the risks of haemolysis in G6PD deficient patients are considered. Primaquine should not be given in pregnancy and in children less than 4 years old.
12.2. Mass screening and treatment
Mass screening for parasitaemia and treating all infected persons in a targeted area or population, irrespective of whether they are symptomatic aims to reduce the size of the infectious reservoir in the targeted area. Mass screening and treatment may be indicated in areas where the parasite reservoir (or parasite gene pool) needs to be quickly and selectively reduced. This type of intervention also plays a significant role in reducing the infectious reservoir of parasites in a given location and is very useful in the pre-elimination and elimination phases of malaria control.17 It requires considerable logistics, capacity and preparation.
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Mass screening and treatment is not the same as and must not be confused with Mass Drug Administration, which is the administration of a complete treatment course of antimalarial medicines to every individual in a geographically defined area on a specific day.
