T he Republic of Djibouti, bordered by Eritrea, Ethiopia, and Somalia, is a semiarid country in the Horn of Africa. The population comprises <900,000 persons, 70% of whom live in Djibouti, the capital city. Before 2013, malaria was hypoendemic to the country, with low levels of transmission in periruban and rural areas during December-May. Localized outbreaks occurred regularly, possibly caused by migration from surrounding countries. Most cases were caused by infection with Plasmodium falciparum (>80%) or P. vivax. Before 2013, researchers considered the Anopheles arabiensis mosquito to be the primary vector (1).The incidence of malaria had drastically decreased in the country since 2008; by 2012, this transmission level was compatible with preelimination goals (2,3). In 2013, an autochthonous outbreak of malaria occurred in Djibouti; fi eld entomologic investigations identifi ed An. stephensi mosquitoes as a new malaria vector (4). This species, a known vector of urban malaria in India and the Arabian Peninsula, has changed the epidemiologic profi le of malaria in Djibouti (5). In 2018, malaria incidence increased to 25,319 confi rmed cases (64% caused by P. falciparum and 36% by P. vivax) and >100,000 suspected cases (Appendix Figure 1, https://wwwnc.cdc.gov/EID/ article/27/6/20-4557-App1.pdf).The French Armed Forces (FAF) have served in Djibouti for decades. Service members and their families (≈2,700 persons) live in the capital. Despite malaria prevention and treatment measures described elsewhere (6), an outbreak among French military personnel occurred in February 2019; failure of early artemisinin combined therapy was documented in 1 patient. The StudyWe collated FAF epidemiologic surveillance data on malaria cases among service members in Djibouti during 1993Djibouti during -2019; the 2019 data included cases among family members. We defi ned a malaria case as an illness resulting in a positive result on a rapid diagnostic test or thin blood smear.We conducted the fi eld investigation in the capital during February 28-March 22, 2019. We obtained a dried blood spot on fi lter paper from each patient and stored the samples in a sealed plastic pouch until processing. We extracted DNA from the samples and

Artemisinin derivatives were shown to be unstable in vitro and their addition as fractional doses could partly compensate for this instability. Importantly, the cellular physiological condition was a determinant of their antiviral activity.

BackgroundDihydroartemisinin-piperaquine is a new ACT that is administered as single daily dose for three days and has been demonstrated to be tolerated and highly effective for the treatment of uncomplicated Plasmodium falciparum malaria. Piperaquine was used alone to replace chloroquine as the first-line treatment for uncomplicated malaria in China in response to increasing chloroquine resistance in the 1970s. However, the rapid emergence of piperaquine-resistant strains that resulted in the cessation of its use in China in the 1980s, suggests that there is cross-resistance between piperaquine and chloroquine. Very few data are available on cross-resistance between piperaquine and chloroquine, and the data that do exist are often contradictory.MethodsIn total, 280 P. falciparum isolates, collected between April 2008 and June 2012 from patients hospitalized in France with imported malaria from a malaria-endemic country, were assessed ex vivo for piperaquine and chloroquine susceptibilities by using the standard 42-hour 3H-hypoxanthine uptake inhibition method. The chloroquine resistance-associated mutation K76T in pfcrt was also investigated for the 280 isolates.ResultsThe IC50 for piperaquine ranged from 9.8 nM to 217.3 nM (mean = 81.3 nM. The IC50 for chloroquine ranged from 5.0 nM to 1,918 nM (mean = 83.6 nM. A significant but low correlation was observed between the Log IC50 values for piperaquine and chloroquine (r = 0.145, p < 0.001). However, the coefficient of determination of 0.021 indicates that only 2.1% of the variation in the response to piperaquine is explained by the variation in the response to chloroquine. The mean value for piperaquine was 74.0 nM in the Pfcrt K76 wild-type group (no = 125) and 87.7 nM in the 76 T mutant group (no = 155). This difference was not significant (p = 0.875, Mann Whitney U test).ConclusionsThe present work demonstrates that there was no cross-resistance between piperaquine and chloroquine among 280 P. falciparum isolates and that piperaquine susceptibility is not associated with pfcrt, the gene involved in chloroquine resistance. These results confirm the efficacy of piperaquine in association with dihydroartemisinin and support its use in areas in which parasites are resistant to chloroquine.

BackgroundA better anti-malarial efficiency and lower neurotoxicity have been reported for mefloquine (MQ) (+)- enantiomer. However, the importance of stereoselectivity remains poorly understood as the anti-malarial activity of pure enantiomer MQ analogues has never been described. Building on these observations, a series of enantiopure 4-aminoalcohol quinoline derivatives has previously been synthesized to optimize the efficiency and reduce possible adverse effects. Their in vitro activity on Plasmodium falciparum W2 and 3D7 strains is reported here along with their inhibition of β-haematin formation and peroxidative degradation of haemin, two possible mechanisms of action of anti-malarial drugs.ResultsThe (S)-enantiomers of this series of 4-aminoalcohol quinoline derivatives were found to be at least as effective as both chloroquine (CQ) and MQ. The derivative with a 5-carbon side-chain length was the more efficient on both P. falciparum strains. (R )-enantiomers displayed an activity decreased by 2 to 15-fold as compared to their (S) counterparts. The inhibition of β-haematin formation was significantly stronger with all tested compounds than with MQ, irrespective of the stereochemistry. Similarly, the inhibition of haemin peroxidation was significantly higher for both (S) and (R)-enantiomers of derivatives with a side-chain length of five or six carbons than for MQ and CQ.ConclusionsThe prominence of stereochemistry in the anti-malarial activity of 4-aminoalcohol quinoline derivatives is confirmed. The inhibition of β-haematin formation and haemin peroxidation can be put forward as presumed mechanisms of action but do not account for the stereoselectivity of action witnessed in vitro.

BackgroundStephania rotunda is used by traditional health practitioners in Southeast Asia to treat a wide range of diseases and particularly symptoms related to malaria. Cepharanthine (CEP) is an alkaloid isolated from this plant with potential innovative antiplasmodial activity. The analysis of interactions between antiplasmodial drugs is necessary to develop new drugs combinations to prevent de novo emergence of resistance. The objective of this study was to evaluate the anti-malarial activity of CEP in combination with usual anti-malarial compounds, both in vitro and in vivo.MethodsA fixed ratio method using the isotopic micro test was performed on the chloroquine-resistant plasmodial strain W2 to build isobolograms from eight CEP-based combinations with standard anti-malarial drugs. The efficacy of two combinations was then evaluated in the BALB/c mouse infected with Plasmodium berghei ANKA strain.ResultsIn vitro, efficiency gains were observed when CEP was combined with chloroquine (CQ), lumefantrine (LUM), atovaquone (ATO), piperaquine (PPQ) and particularly monodesethylamodiaquine (MdAQ), whereas an antagonistic interaction was observed with dihydroartemisinin (DHA) and mefloquine (MQ). In vivo, the combination of CEP with CQ or amodiaquine (AQ) improved significantly the survival of mice and extended the delay for parasitic recrudescence.ConclusionAll these observations suggest that CEP could be an interesting lead compound in the development of a combination therapy against malaria.