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ANNEX 4. Antimalarials and malaria transmission

gametocytes, which may be present in the circulation at the time of treatment (12).
Primaquine, an 8-aminoquinoline, which is widely used as a hypnozoiticidal drug
for the prevention of relapses in P. vivax, acts on mature gametocytes and accelerates
gametocyte clearance (12). The addition of primaquine to ACTs in the treatment of
P. falciparum infections will be beneficial, because the latter acts on mature infective
gametocytes on which artemisinins have little or no effect (14).

Table A4.1 Effects of some commonly used antimalarials on the infectivity
of P. falciparum to the mosquito

effect of treatment
Gametocytocidal Sporonticidal
drug Viability of young Viability of Infectivity of Overall effect
sequestered mature circulating gametocytes to on suppressing A4
gametocytes gametocytes mosquitoes infectivity a
Chloroquine Reduces No effect (4) Enhances (5) +
Sulfadoxine- No effect Increases (5–7) Suppresses (5–7) ±
pyrimethamine
Artemisinin Greatly reduces Little effect (11) Unknown +++
derivatives (8–11)
Primaquine Unknown Greatly reduces (11) Unknown +++
Quinine (4) No effect No effect No effect None
a ±: No overall effect; +: moderate effect; ++: high effect; +++: very high effect

a4.2.1 in situations of low-to-moderate transmission

The most direct consequences of lowering parasite infectivity by the use of drugs are to
be seen in areas of low transmission where symptomatic patients constitute the majority
of the infectious reservoir. Here a strategy to shorten the period of infectivity of patients,
as well as to reduce the infectiousness of gametocytes, will have a significant impact on
malaria transmission. A reduction in transmission would, in these situations, result in an
almost proportionate reduction in the prevalence of infection and incidence of disease.
In areas of low-to-moderate transmission, therefore, the provision of prompt and
effective treatment to malaria patients is important, both as a means of achieving the
therapeutic goal of reducing morbidity and mortality, and the public health goal of
reducing transmission. In addition, the use of specific gametocytocidal medicines will
help to curtail transmission.

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