Ex-vivo response of Plasmodium falciparum to Dihydroartemisinin in an area of Ota South-west Nigeria

Abstract

Artemisinin drugs remain the mainstay of falciparum malaria control globally. Ring-stage survival assay (RSA) is a simple new method that can be used for detecting artemisinin resistance, thus this study aims to determine ex-vivo parasite susceptibility to dihydroartemisinin and its correlation with in-vivo parasite response to artemisinin combinations in an endemic area of Nigeria. Using the simple and sensitive ring-stage survival assay (RSA), 50 parasite isolates from patients with malaria were exposed to DHA concentrations for 6 hours and ring stage survival was determined by microscopy within 72hours of drug exposure. In-vivo parasite clearance was compared with parasite survival in matched patient samples. Parasitemia cleared rapidly within 24hours (mean 22.4 ± 0.2h) in all subjects. There was a dose-dependent growth inhibition in drug-exposed plates, and ring-stage growth inhibition correlated positively with parasite clearance rates in all samples (r = 0.97, p<0.0001). P. falciparum isolates from this endemic area show sensitivity to artemisinin drugs both in-vivo and ex-vivo. The RSA method has potential to detect declines in parasite responses to artemisinins and can be used for continuous monitoring of responses especially in areas where resistance has not emerged.