How do you tell whether a person is infected with Plasmodium falciparum, the parasite responsible for malaria? Finding out is very difficult, because at certain stages of its development, the parasite causes no symptoms, and is invisible in a drop of blood observed through a microscope. However, this situation may change, thanks to the work of a team of researchers with which the IRD is associated. The team has just developed a saliva test that detects a protein expressed by the gametocytes (sexual stages) of P. falciparum(1). Although asymptomatic in human beings, the parasite in this stage is a reservoir of the disease: it can develop in the mosquito and be transmitted to other individuals.
In a first experiment, 364 school-age children in Cameroon and Zambia gave their saliva by splitting into small tubes: a non-invasive sampling method often taken for a game. In the samples, the researchers were able to identify asymptomatic carriers of malaria and give them early curative treatment. The aim is to treat carriers and limit transmission of the parasite: a major challenge in these regions, where the disease is highly prevalent: over 50% of children in education are asymptomatic carriers. New tests will be carried out in 2019, to develop and validate a prototype saliva test that could be rolled out more widely in central Africa in 2020.
Dingyin Tao, Brent McGill, Timothy Hamerly, Tamaki Kobayashi, Prachi Khare, Amanda Dziedzic, Tomasz Leski, Andrew Holtz, Bruce Shull, Anne E. Jedlicka, Andrew Walzer, Paul D. Slowey, Christopher C. Slowey, Sandrine E. Nsango, David A. Stenger, Mike Chaponda, Modest Mulenga, Kathryn H. Jacobsen, David J. Sullivan, Sadie J. Ryan, Rashid Ansumana, William J. Moss, Isabelle Morlais, Rhoel R. Dinglasan. A saliva-based rapid test to quantify the infectious subclinical malaria parasite reservoir, Science Translational Medicine, 2 janvier 2019
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