The World Health Organization recommends that patients with uncomplicated malaria be treated with a combination of two unrelated drugs, with the currently preferred option being Artemisinin Combination Therapies (ACTs). Drugs with gametocytoidal activity have the potential to reduce the transmission potential of malaria and decrease the spread of drug resistant parasites.
Unlike most schizontocidal agents the artemisinin derivatives have activity against the stage II-IV gametocyte sexual stages. However the consequences of this gametocytocidal activity varies depending on the drug regimen, the doses given, the local prevalence of drug resistance and host immunity.
A variety of confounding factors have been associated with gametocyte carriage including: presentation with fever, a high asexual parasitaemia, age, anaemia, pure infection of P. falciparum and a palpable spleen. Furthermore the metrics for measuring gametocyte carriage vary considerably from simple proportions of patients who have gametocytes observed during follow up, to measures of incidence density and ultimately to the infectivity of the patients’ blood to mosquitoes. Whilst there is good evidence that ACTs are associated with a significant reduction in gametocyte carriage, the crucial factor is the ability of patients to infect the mosquito vector.
The public health benefit of different ACTs and their ability to reduce malaria transmission are now crucial factors that need to be considered as part of decisions on antimalarial policy. There is an urgent need to review gametocyte carriage across a variety of settings using standardised analytical approaches, controlling for confounding factors.