The PRINOGAM trial on the use of low doses of primaquine to interrupt malaria transmission from human to mosquitoes in individuals not sick but with a malaria infection has been successfully completed.
Malaria is a parasitic disease transmitted by Anopheles mosquitoes. The parasite is usually present as sexual and asexual forms in the blood stream. Though the sexual form does not cause disease, it’s responsible for transmitting infection from the human host to the mosquito vector.

To find new tools to interrupt malaria transmission, the Disease Control and Elimination Theme of the MRC Unit The Gambia embarked on a clinical trial called Primaquine’s gametocytocidal efficacy in malaria asymptomatic carriers treated with dihydroartemisinin-piperaquine in The Gambia (PRINOGAM). The trial is funded by the Global Health Trial Scheme (MRC/DfID and Wellcome Trust) and led by Professor Umberto D’Alessandro Principal Investigator (PI) and coordinated by Dr Joseph Okebe. The trial was conducted first in Basse and Jahaly, and then in Basse only.

Interventions to reduce the transfer of parasite sexual forms, called gametocytes, from man to mosquito may have a significant impact on malaria transmission and the overall burden of diseases. Previous research has shown that the only available treatment against gametocytes is primaquine that may cause anaemia in people with a deficiency of a specific enzyme, which is genetically determined. In these people, the risk of anaemia is related to the dose of primaquine given. The main objective of the trial was to determine the lowest possible dose of primaquine having similar activity against gametocytes than the recommended one and thus with a lower risk of anaemia.

The result findings provide the necessary data for the potential use of a lower than recommended dose of primaquine to eliminate gametocytes from malaria infected individuals, hence the potential for reducing transmission. The results of this study will be used to determine the feasibility of deploying primaquine on a large scale in sub-Saharan Africa, where the malaria burden is the highest, and may contribute to the drive towards malaria pre-elimination/elimination in this continent.

According to the PI Professor Umberto D’Alessandro, “further research is required to find out if the lowest efficacious dose is also safe in people at risk of anaemia. If yes, we could carry out a large, community-based trial to look at the impact on malaria transmission.”