Dihydroartemisinin-piperaquine treatment failure of uncomplicated Plasmodium falciparum malaria infection in a traveller

We report a late dihydroartemisinin–piperaquine treatment failure of uncomplicated Plasmodium falciparum malaria infection in a traveller without evidence of drug resistance. The correct treatment intake was confirmed, isolates drugs susceptibility was confirmed by RSA-PSA and chemosusceptibility. No molecular markers associated with resistance to artemisinin derivatives or piperaquine were identified.

Assessment of the Performance of Lactate Dehydrogenase-Based Rapid Diagnostic Test for Malaria in Djibouti in 2022-2023

Until 2020, Djiboutian health authorities relied on histidine-rich protein-2 (HRP2)-based rapid diagnostic tests (RDTs) to establish the diagnosis of Plasmodium falciparum. The rapid spread of P. falciparum histidine-rich protein-2 and -3 (pfhrp2/3) gene-deleted parasite strains in Djibouti has led the authorities to switch from HRP2-based RDTs to lactate dehydrogenase (LDH)-based RDTs targeting the plasmodial lactate dehydrogenase (pLDH) specific for P. falciparum and P. vivax (RapiGEN BIOCREDIT Malaria Ag Pf/Pv pLDH/pLDH) in 2021. This study was conducted with the primary objective of evaluating the diagnostic performance of this alternative RDT. Operational constraints related, in particular, to the implementation of this RDT during the COVID-19 pandemic were also considered. The performance of BIOCREDIT Malaria Ag Pf/Pv (pLDH/pLDH) RDT was also compared to our previously published data on the performance of two HRP2-based RDTs deployed in Djibouti in 2018-2020. The diagnosis of 350 febrile patients with suspected malaria in Djibouti city was established using two batches of RapiGEN BIOCREDIT Malaria Ag Pf/Pv (pLDH/pLDH) RDT over a two-year period (2022 and 2023) and confirmed by real-time quantitative polymerase chain reaction. The sensitivity and specificity for the detection of P. falciparum were 88.2% and 100%, respectively. For P. vivax, the sensitivity was 86.7% and the specificity was 100%. Re-training and closer supervision of the technicians between 2022 and 2023 have led to an increased sensitivity to detect P. falciparum (69.8% in 2022 versus 88.2% in 2023; p < 0.01). The receiver operating characteristic curve analysis highlighted a better performance in the diagnosis of P. falciparum with pLDH-based RDTs compared with previous HRP2-based RDTs. In Djibouti, where pfhrp2-deleted strains are rapidly gaining ground, LDH-based RDTs seem to be more suitable for diagnosing P. falciparum than HRP2-based RDTs. Awareness-raising and training for technical staff have also been beneficial.

Molecular investigation of malaria-infected patients in Djibouti city (2018-2021)

BACKGROUND

The Republic of Djibouti is a malaria endemic country that was in pre-elimination phase in 2006-2012. From 2013, however, malaria has re-emerged in the country, and its prevalence has been increasing every year. Given the co-circulation of several infectious agents in the country, the assessment of malaria infection based on microscopy or histidine-rich protein 2 (HRP2)-based rapid diagnostic tests (RDT) has shown its limitations. This study, therefore, aimed to assess the prevalence of malaria among febrile patients in Djibouti city using more robust molecular tools.

METHODS

All suspected malaria cases reported to be microscopy-positive were randomly sampled (n = 1113) and included in four health structures in Djibouti city over a 4-year period (2018-2021), mainly during the malaria transmission season (January-May). Socio-demographic information was collected, and RDT was performed in most of the included patients. The diagnosis was confirmed by species-specific nested polymerase chain reaction (PCR). Data were analysed using Fisher's exact test and kappa statistics.

RESULTS

In total, 1113 patients with suspected malaria and available blood samples were included. PCR confirmed that 788/1113 (70.8%) were positive for malaria. Among PCR-positive samples, 656 (83.2%) were due to Plasmodium falciparum, 88 (11.2%) Plasmodium vivax, and 44 (5.6%) P. falciparum/P. vivax mixed infections. In 2020, P. falciparum infections were confirmed by PCR in 50% (144/288) of negative RDTs. After the change of RDT in 2021, this percentage decreased to 17%. False negative RDT results were found more frequently (P < 0.05) in four districts of Djibouti city (Balbala, Quartier 7, Quartier 6, and Arhiba). Malaria occurred less frequently in regular bed net users than in non-users (odds ratio [OR]: 0.62, 95% confidence interval [CI]: 0.42-0.92).

CONCLUSIONS

The present study confirmed the high prevalence of falciparum malaria and, to a lesser extent, vivax malaria. Nevertheless, 29% of suspected malaria cases were misdiagnosed by microscopy and/or RDT. There is a need to strengthen the capacity for diagnosis by microscopy and to evaluate the possible role of P. falciparum hrp2 gene deletion, which leads to false negative cases of P. falciparum.

Changing epidemiology of Plasmodium vivax malaria in Nouakchott, Mauritania: a six-year (2015-2020) prospective study

BACKGROUND

Plasmodium vivax malaria is one of the major infectious diseases of public health concern in Nouakchott, the capital city of Mauritania and the biggest urban setting in the Sahara. The assessment of the current trends in malaria epidemiology is primordial in understanding the dynamics of its transmission and developing an effective control strategy.

METHODS

A 6 year (2015-2020) prospective study was carried out in Nouakchott. Febrile outpatients with a clinical suspicion of malaria presenting spontaneously at Teyarett Health Centre or the paediatric department of Mother and Children Hospital Centre were screened for malaria using a rapid diagnostic test, microscopic examination of Giemsa-stained blood films, and nested polymerase chain reaction. Data were analysed using Microsoft Excel and GraphPad Prism and InStat software.

RESULTS

Of 1760 febrile patients included in this study, 274 (15.5%) were malaria-positive by rapid diagnostic test, 256 (14.5%) were malaria-positive by microscopy, and 291 (16.5%) were malaria-positive by PCR. Plasmodium vivax accounted for 216 of 291 (74.2%) PCR-positive patients; 47 (16.1%) and 28 (9.6%) had P. falciparum monoinfection or P. vivax-P. falciparum mixed infection, respectively. During the study period, the annual prevalence of malaria declined from 29.2% in 2015 to 13.2% in 2019 and 2.1% in 2020 (P < 0.05). Malaria transmission was essentially seasonal, with a peak occurring soon after the rainy season (October-November), and P. vivax infections, but not P. falciparum infections, occurred at low levels during the rest of the year. The most affected subset of patient population was adult male white and black Moors. The decline in malaria prevalence was correlated with decreasing annual rainfall (r = 0.85; P = 0.03) and was also associated with better management of the potable water supply system. A large majority of included patients did not possess or did not use bed nets.

CONCLUSIONS

Control interventions based on prevention, diagnosis, and treatment should be reinforced in Nouakchott, and P. vivax-specific control measures, including chloroquine and 8-aminoquinolines (primaquine, tafenoquine) for treatment, should be considered to further improve the efficacy of interventions and aim for malaria elimination.

Mycobacterium ulcerans Experimental Dormancy

Whether Mycobacterium ulcerans, the etiological agent of Buruli ulcer in numerous tropical countries, would exist in a dormant state as reported for closely related Mycobacterium species, has not been established. Six M. ulcerans strains were exposed to a progressive depletion in oxygen for 2 months, using the Wayne model of dormancy previously described for M. tuberculosis, and further examined by microscopy after staining of dynamic, dormant, and dead mycobacteria (DDD staining), microcalorimetry and subculture in the presence of dead and replicative M. ulcerans as controls. Mycobacterium ulcerans CU001 strain died during the progressive oxygen depletion and four of five remaining strains exhibited Nile red-stained intracellular lipid droplets and a 14- to 20-day regrowth when exposed to ambient air, consistent with dormancy. A fifth M. ulcerans 19423 strain stained negative in DDD staining and slowly regrew in 27 days. Three tested M. ulcerans strains yielded microcalorimetric pattern similar to that of the negative (dead) homologous controls, differing from that of the homologous positive (replicative) controls. The relevance of these experimental observations, suggesting a previously unreported dormancy state of M. ulcerans, warrants further investigations in the natural ecological niches where M. ulcerans thrive as well as in Buruli ulcer lesions.

Methylene blue inhibits replication of SARS-CoV-2 in vitro

In December 2019, a novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing coronavirus diseases 2019 (COVID-19) emerged in Wuhan, China. Currently there is no antiviral treatment recommended against SARS-CoV-2. Identifying effective antiviral drugs is urgently required. Methylene blue has already demonstrated in vitro antiviral activity in photodynamic therapy as well as antibacterial, antifungal and antiparasitic activities in non-photodynamic assays. In this study. non-photoactivated methylene blue showed in vitro activity at very low micromolar range with an EC₅₀ (median effective concentration) of 0.30 ± 0.03 μM and an EC₉₀ (90% effective concentration) of 0.75 ± 0.21 μM at a multiplicity of infection (MOI) of 0.25 against SARS-CoV-2 (strain IHUMI-3). The EC₅₀ and EC₉₀ values for methylene blue are lower than those obtained for hydroxychloroquine (1.5 μM and 3.0 μM) and azithromycin (20.1 μM and 41.9 μM). The ratios C_max/EC₅₀ and C_max/EC₉₀ in blood for methylene blue were estimated at 10.1 and 4.0, respectively, following oral administration and 33.3 and 13.3 following intravenous administration. Methylene blue EC₅₀ and EC₉₀ values are consistent with concentrations observed in human blood. We propose that methylene blue is a promising drug for treatment of COVID-19. In vivo evaluation in animal experimental models is now required to confirm its antiviral effects on SARS-CoV-2. The potential interest of methylene blue to treat COVID-19 needs to be confirmed by prospective comparative clinical studies.

Genetic diversity of Plasmodium falciparum in Grande Comore Island

Background

Despite several control interventions resulting in a considerable decrease in malaria prevalence in the Union of the Comoros, the disease remains a public health problem with high transmission in Grande Comore compared to neighbouring islands. In this country, only a few studies investigating the genetic diversity of Plasmodium falciparum have been performed so far. For this reason, this study aims to examine the genetic diversity of P. falciparum by studying samples collected in Grande Comore in 2012 and 2013, using merozoite surface protein 1 (msp1), merozoite surface protein 2 (msp2) and single nucleotide polymorphism (SNP) genetic markers.

Methods

A total of 162 positive rapid diagnostic test (RDT) samples from Grande Comore were used to extract parasite DNA. Allelic families K1, Mad20 and RO33 of the msp1 gene as well as allelic families IC3D7 and FC37 of the msp2 gene were determined by using nested PCR. Additionally, 50 out of 151 samples were genotyped to study 24 SNPs by using high resolution melting (HRM).

Results

Two allelic families were predominant, the K1 family of msp1 gene (55%) and the FC27 family of msp2 gene (47.4%). Among 50 samples genotyped for 24 SNPs, 42 (84%) yielded interpretable results. Out of these isolates, 36 (85%) were genetically unique and 6 (15%) grouped into two clusters. The genetic diversity of P. falciparum calculated from msp1 and msp2 genes and SNPs was 0.82 and 0.61, respectively.

Conclusion

In summary, a large genetic diversity of P. falciparum was observed in Grande Comore. This may favour persistence of malaria and might be one of the reasons for the high malaria transmission compared to neighbouring islands. Further surveillance of P. falciparum isolates, mainly through environmental management and vector control, is warranted until complete elimination is attained.

Antimalarial drugs inhibit the replication of SARS-CoV-2: An in vitro evaluation

In December 2019, a new severe acute respiratory syndrome coronavirus (SARS-CoV-2) causing coronavirus diseases 2019 (COVID-19) emerged in Wuhan, China. African countries see slower dynamic of COVID-19 cases and deaths. One of the assumptions that may explain this later emergence in Africa, and more particularly in malaria endemic areas, would be the use of antimalarial drugs. We investigated the in vitro antiviral activity against SARS-CoV-2 of several antimalarial drugs. Chloroquine (EC50 = 2.1 μM and EC90 = 3.8 μM), hydroxychloroquine (EC50 = 1.5 μM and EC90 = 3.0 μM), ferroquine (EC50 = 1.5 μM and EC90 = 2.4 μM), desethylamodiaquine (EC50 = 0.52 μM and EC90 = 1.9 μM), mefloquine (EC50 = 1.8 μM and EC90 = 8.1 μM), pyronaridine (EC50 = 0.72 μM and EC90 = 0.75 μM) and quinine (EC50 = 10.7 μM and EC90 = 38.8 μM) showed in vitro antiviral effective activity with IC50 and IC90 compatible with drug oral uptake at doses commonly administered in malaria treatment. The ratio Clung/EC90 ranged from 5 to 59. Lumefantrine, piperaquine and dihydroartemisinin had IC50 and IC90 too high to be compatible with expected plasma concentrations (ratio Cmax/EC90 < 0.05). Based on our results, we would expect that countries which commonly use artesunate-amodiaquine or artesunate-mefloquine report fewer cases and deaths than those using artemether-lumefantrine or dihydroartemisinin-piperaquine. It could be necessary now to compare the antimalarial use and the dynamics of COVID-19 country by country to confirm this hypothesis.

Prevalence of mutations in the Plasmodium falciparum chloroquine resistance transporter, PfCRT, and association with ex vivo susceptibility to common anti-malarial drugs against African Plasmodium falciparum isolates

Background

The Plasmodium falciparum chloroquine transporter gene (pfcrt) is known to be involved in chloroquine and amodiaquine resistance, and more particularly the mutations on the loci 72 to 76 localized within the second exon. Additionally, new mutations (T93S, H97Y, C101F, F145I, M343L, C350R and G353V) were recently shown to be associated with in vitro reduced susceptibility to piperaquine in Asian or South American P. falciparum strains. However, very few data are available on the prevalence of these mutations and their effect on parasite susceptibility to anti-malarial drugs, and more particularly piperaquine in Africa.

Methods

A molecular investigation of these mutations was performed in 602 African P. falciparum parasites collected between 2017 and 2018 on malaria patients hospitalized in France after a travel in African countries. Associations between genotypes and in vitro susceptibilities to piperaquine and standard antimalarial drugs were assessed.

Results

None of the mutations, previously described as associated with piperaquine resistance, was found in the 602 P. falciparum African isolates. The K76T mutation is associated with resistance to chloroquine (p < 0.0002) and desethylamodiaquine (p < 0.002) in Africa. The K76T mutation is not associated with in vitro reduced susceptibility to piperaquine. The mutation I356T, identified in 54.7% (n = 326) of the African isolates, was significantly associated with reduced susceptibility to quinine (p < 0.02) and increased susceptibility to mefloquine (p < 0.04). The K76T and I356T mutations were significantly associated in West African isolates (p = 0.008).

Conclusion

None of the mutations in pfcrt found to be associated with piperaquine reduced susceptibility in Asia or South America (T93S, H97Y, C101F, F145I, M343L C350R and G353V) were found in the 602 African isolates including the three isolates with reduced susceptibility to piperaquine. The K76T mutation, involved in resistance to chloroquine and amodiaquine, and the I356T mutation were not associated with in vitro reduced susceptibility to piperaquine. Differences in mefloquine susceptibility between I356 and 356T isolates were, while statistically different, minimal. Further analyses are needed with a more important sample size from the same geographic area to confirm the role of the I356T mutation on quinine susceptibility.

Malaria epidemiology in Kobeni department, southeastern Mauritania from 2015 to 2017

Background

Plasmodium falciparum malaria is endemic in the southern sahelian zone of Mauritania where intense internal and trans-border human and livestock movement occurs. The risk of importation and spread of drug-resistant parasites need to be regularly assessed in this region. The objective of the study was to assess the recent malaria situation near the Mauritania-Mali border.

Methods

Between February 2015 and December 2017, patients with fever or history of fever during the previous 48 h, presenting at the health centre of Kobeni city, were screened for malaria using a rapid diagnostic test (RDT) and microscopic examination of blood smears. The diagnosis was later confirmed by PCR. Cohen’s kappa statistics was used to estimate the degree of agreement between diagnostic methods. Fisher’s exact test was used to compare proportions. The odds ratio was calculated to measure the association between the use of bed nets and malaria infection.

Results

A total of 2326 febrile patients (mean age, 20.2 years) were screened for malaria. The presence of malaria parasites was detected by RDT and microscopy in 53.0% and 49.3% of febrile patients, respectively, and was confirmed by PCR in 59.7% (45 missing data). Of 1361 PCR-positive samples, 1205 (88.5%) were P. falciparum, 47 (3.5%) P. vivax, and 99 (7.3%) P. falciparum-P. vivax mixed infection. Malaria transmission occurred mostly during and shortly after the rainy season. The annual rainfall was relatively low in 2016 (267 mm) and 2017 (274 mm), compared to 2015 (448 mm), and coincided with a decline in malaria prevalence in 2016–2017. Although 71.8% of febrile patients reported to possess at least one bed net in the household in our questionnaire, its reported use was not protective against malaria infection (odds ratio: 1.1, 95% CI: 0.91–1.32).

Conclusions

Our study confirmed that P. falciparum is the dominant species in the sahelian zone and that malaria transmission is seasonal and associated with rainfall in this zone. The application of the current national policy based on rapid and reliable malaria diagnosis, case management with artemisinin-based combination therapy, intermittent preventive treatment for pregnant women, distribution and use of long-lasting insecticide impregnated bed nets, and the planned introduction of seasonal malaria chemoprevention for all children under 6 years old is expected to sustainably reduce malaria transmission in this zone.

Assessment of glucose-6-phosphate dehydrogenase activity using CareStart G6PD rapid diagnostic test and associated genetic variants in Plasmodium vivax malaria endemic setting in Mauritania

Background

Primaquine is recommended by the World Health Organization (WHO) for radical treatment of Plasmodium vivax malaria. This drug is known to provoke acute hemolytic anemia in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Due to lack of data on G6PD deficiency, the use of primaquine has been limited in Africa. In the present study, G6PD deficiency was investigated in blood donors of various ethnic groups living in Nouakchott, a P. vivax endemic area in Mauritania.

Methodology/Principal findings

Venous blood samples from 443 healthy blood donors recruited at the National Transfusion Center in Nouakchott were screened for G6PD activity using the CareStart G6PD deficiency rapid diagnostic test. G6PD allelic variants were investigated using DiaPlexC G6PD genotyping kit that detects African (A^-) and Mediterranean (B^-) variants. Overall, 50 of 443 (11.3%) individuals (49 [11.8%] men and 1 [3.7%] woman) were phenotypically deficient. Amongst men, Black Africans had the highest prevalence of G6PD deficiency (15 of 100 [15%]) and White Moors the lowest (10 of 168, [5.9%]). The most commonly observed G6PD allelic variants among 44 tested G6PD-deficient men were the African variant A^- (202A/376G) in 14 (31.8%), the Mediterranean variant B^- (563T) in 13 (29.5%), and the Betica-Selma A^- (376G/968C) allelic variant in 6 (13.6%). The Santamaria A^- variant (376G/542T) and A variant (376G) were observed in only one and two individuals, respectively. None of the expected variants was observed in 8 (18.2%) of the tested phenotypically G6PD-deficient men.

Conclusion

This is the first published data on G6PD deficiency in Mauritanians. The prevalence of phenotypic G6PD deficiency was relatively high (11.3%). It was mostly associated with either African or Mediterranean variants, in agreement with diverse Arab and Black African origins of the Mauritanian population.

Oasis Malaria, Northern Mauritania1

A malaria survey was conducted in Atar, the northernmost oasis city in Mauritania, during 2015–2016. All febrile patients in whom malaria was suspected were screened for malaria by using rapid diagnostic testing and microscopic examination of blood smears and later confirmed by PCR. Of 453 suspected malaria cases, 108 (23.8%) were positive by rapid diagnostic testing, 154 (34.0%) by microscopic examination, and 162 (35.7%) by PCR. Malaria cases were observed throughout the year and among all age groups. Plasmodium vivax was present in 120/162 (74.1%) cases, P. falciparum in 4/162 (2.4%), and mixed P. falciparum–P. vivax in 38/162 (23.4%). Malaria is endemic in northern Mauritania and could be spreading farther north in the Sahara, possibly because of human-driven environmental changes. Further entomologic and parasitologic studies and monitoring are needed to relate these findings to major Anopheles mosquito vectors and to design and implement strategies for malaria prevention and control.

Investigation of a possible malaria epidemic in an illegal gold mine in French Guiana: an original approach in the remote Amazonian forest

Background

In April 2017, Suriname’s Ministry of Health alerted French Guiana’s Regional Health Agency (RHA) about an increase of imported malaria cases among people coming from an illegal gold mining site called Sophie, in French Guiana, a French overseas territory located in the Amazonian forest.

Methods

Due to safety issues and the remoteness of Sophie, the RHA requested the collaboration of the French Armed Forces for the epidemiological investigation. A medical unit, and six soldiers to ensure the security of the mission, were transported by helicopter.

Results

During the investigation, two malaria episodes were diagnosed among 46 persons. Twenty-six of them were from Sophie, where PCR-Plasmodium prevalence was estimated at 60% (15/26). This result was concordant with previous studies revealing high malaria endemicity in the gold miner population. The increase of imported cases in Suriname may have resulted from decreased access to under-the-counter anti-malarials and increased migration of gold miners to Suriname following a decline of the profitability of gold mining in a context of increased repression against illegal mining by the French army.

Conclusion

This investigation of a suspicious malaria epidemic confirms the importance of malaria among illegal gold miners. Their mobility along the Guiana Shield and their health-seeking behaviour are likely to spread malaria in populations for which significant efforts are undertaken to fight against this disease. Fighting malaria in this population remains more relevant than ever. A pilot study (Malakit project) is currently in progress to evaluate the efficacy of kits for self-diagnosis and self-treatment.

Epidemiological and molecular forensics of cholera recurrence in Haiti

Cholera has affected Haiti with damping waves of outbreaks since October 2010. However, mechanisms behind disease persistence during lull periods remain poorly understood. By mid 2014, cholera transmission seemed to only persist in the northern part of Haiti. Meanwhile, cholera appeared nearly extinct in the capital, Port-au-Prince, where it eventually exploded in September 2014. This study aimed to determine whether this outbreak was caused by local undetected cases or by re-importation of the disease from the north. Applying an integrated approach between November 2013 and November 2014, we assessed the temporal and spatial dynamics of cholera using routine surveillance data and performed population genetics analyses of 178 Vibrio cholerae O1 clinical isolates. The results suggest that the northern part of the country exhibited a persisting metapopulation pattern with roaming oligoclonal outbreaks that could not be effectively controlled. Conversely, undetected and unaddressed autochthonous low-grade transmission persisted in the Port-au-Prince area, which may have been the source of the acute outbreak in late-2014. Cholera genotyping is a simple but powerful tool to adapt control strategies based on epidemic specificities. In Haiti, these data have already yielded significant progress in cholera surveillance, which is a key component of the strategy to eventually eliminate cholera.

Pyrethroid resistance in the major malaria vector Anopheles arabiensis in Nouakchott, Mauritania

BACKGROUND

Mauritania is one of the African countries with ongoing malaria transmission where data on insecticide resistance of local malaria vectors are limited despite an increasing use of long-lasting insecticide-treated nets (LLINs) as the main intervention for vector control. This study presents an evaluation of the level of insecticide resistance of Anopheles arabiensis in Nouakchott.

METHODS

Anopheles gambiae (s.l.) larvae were collected in breeding sites during the rainy season (August-September) in 2015 and 2016 from two selected sites in Nouakchott and reared until emergence. Adult anopheline mosquitoes were tested against malathion (5%), bendiocarb (0.1%), permethrin (0.75%) and deltamethrin (0.05%) using standard World Health Organization (WHO) insecticide-impregnated papers. PCR assays were used for the identification of An. gambiae (s.l.) sibling species as well as knockdown resistance (kdr).

RESULTS

The mean knockdown times 50% (KDT50) and 95% (KDT95) were 66 ± 17 and 244 ± 13 min, respectively, for permethrin in 2015. The KDT50 and the KDT95 were 39 ± 13 and 119 ± 13 min, respectively, for deltamethrin. The KDT50 and the KDT95 doubled for both molecules in 2016. The mortality rates 24 h post-exposure revealed that An. arabiensis populations in Nouakchott were fully susceptible to bendiocarb and malathion in 2015 as well as in 2016, while they were resistant to permethrin (51.9% mortality in 2015 and 24.1% mortality in 2016) and to deltamethrin (83.7% mortality in 2015 and 39.1% mortality in 2016). The molecular identification showed that Anopheles arabiensis was the only malaria vector species collected in Nouakchott in 2015 and 2016. Both the West and East African kdr mutant alleles were found in An. arabiensis mosquitoes surviving exposure to pyrethroid insecticide, with a high rate of homozygous resistant genotypes (54.3% for the West African kdr mutation and 21.4% for the East African kdr mutation) and a significant departure from Hardy-Weinberg proportions (χ2 = 134, df = 3, P < 0.001).

CONCLUSIONS

The study showed high levels of pyrethroid resistance in An. arabiensis populations in Nouakchott and presence of both West and East African kdr alleles in the resistant phenotype. These results highlight a need for routine monitoring of susceptibility of malaria vector populations to insecticides used in public health programs.

Characterization of Plasmodium falciparum genes associated with drug resistance in Hodh Elgharbi, a malaria hotspot near Malian-Mauritanian border

BACKGROUND

A malaria hotspot in the southeastern region of Mauritania, near the Malian border, may hamper malaria control strategies. The objectives were to estimate the prevalence of genetic polymorphisms associated with drug resistance in Plasmodium falciparum isolates and establish baseline data.

METHODS

The study was conducted in two malaria-endemic areas in Hodh Elgharbi, situated in the Malian-Mauritanian border area. Blood samples were collected from symptomatic patients. Single nucleotide polymorphisms in Pfcrt, Pfmdr1, Pfdhfr, and Pfdhps were genotyped using PCR-restriction fragment length polymorphism, DNA sequencing and primer extension. The Pfmdr1 gene copy number was determined by real-time PCR.

RESULTS

Of 280 P. falciparum-infected patients, 193 (68.9%) carried the Pfcrt 76T mutant allele. The Pfmdr1 86Y and 184F mutations were found in 61 (23.1%) of 264 isolates and 167 (67.6%) of 247 samples that were successfully genotyped, respectively. Pfmdr1 mutant alleles 1034C, 1042D and 1246Y were rarely observed. Of 102 P. falciparum isolates analysed, ten (9.8%) had more than one copy of Pfmdr1 gene. The prevalence of isolates harbouring at least triple mutant Pfdhfr 51I, 59R, 108 N/T was 42% (112/268), of which 42 (37.5%) had an additional Pfdhps 437G mutation. The Pfdhps 540E mutation was observed in four isolates (1.5%), including three associated with Pfdhfr triple mutant. Only two quintuple mutants (Pfdhfr-51I-59R-108N Pfdhps-437G-540E) were observed.

CONCLUSIONS

The observed mutations in Pfdhfr, Pfdhps, Pfmdr1, and Pfcrt may jeopardize the future of seasonal malaria chemoprevention based on amodiaquine-sulfadoxine-pyrimethamine, intermittent preventive treatment for pregnant women using sulfadoxine-pyrimethamine, and treatment with artesunate-amodiaquine. Complementary studies should be carried out to document the distribution, origin and circulation of P. falciparum populations in this region and more widely in the country to assess the risk of the spread of resistance.

Mosquitoes (Diptera: Culicidae) in Mauritania: a review of their biodiversity, distribution and medical importance

Although mosquitoes (Diptera: Culicidae) are important disease vectors, information on their biodiversity in Mauritania is scarce and very dispersed in the literature. Data from the scientific literature gathered in the country from 1948 to 2016 were collected and analyzed. Overall 51 culicid species comprising 17 Anopheles spp., 14 Aedes spp., 18 Culex spp. and two Mansonia spp. have been described in Mauritania among which Anopheles arabiensis, Aedes vexans, Culex poicilipes and Culex antennatus are of epidemiological significance. Anopheles arabiensis is widely distributed throughout the country and its geographic distribution has increased northwards in recent years, shifting its northern limit form 17°32′N in the 1960s to 18°47′N today. Its presence in the central region of Tagant highlights the great ecological plasticity of the species. Conversely, the distribution of Anopheles gambiae (s.s.) and Anopheles melas has shrunk compared to that of the 1960s. Anopheles rhodesiensis and An. d’thali are mainly confined in the mountainous areas (alt. 200–700 m), whereas Anopheles pharoensis is widely distributed in the Senegal River basin. Culex poicilipes and Cx. antenattus were naturally found infected with Rift valley fever virus in central and northern Mauritania following the Rift valley outbreaks of 1998 and 2012. Recently, Ae. aegypti emerged in Nouakchott and is probably responsible for dengue fever episodes of 2015. This paper provides a concise and up-to-date overview of the existing literature on mosquito species known to occur in Mauritania and highlights areas where future studies should fill a gap in knowledge about vector biodiversity. It aims to help ongoing and future research on mosquitoes particularly in the field of medical entomology to inform evidence-based decision-making for vector control and management strategies.

Malaria Hyperendemicity and Risk for Artemisinin Resistance among Illegal Gold Miners, French Guiana

To assess the prevalence of malaria among illegal gold miners in the French Guiana rainforest, we screened 205 miners during May-June 2014. Malaria prevalence was 48.3%; 48.5% of cases were asymptomatic. Patients reported self-medication with artemisinin-based combination therapy. Risk for emergence and spread of artemisinin resistance among gold miners in the rainforest is high.

Circumsporozoite protein rates, blood-feeding pattern and frequency of knockdown resistance mutations in Anopheles spp. in two ecological zones of Mauritania

Background

Mosquitoes belonging to Anopheles gambiae species complex are the main malaria vector in Mauritania but data on their vector capacities, feeding habits and insecticide susceptibility are still scanty. The objectives of this study were to fill this gap.

Methods

Adult Anopheles spp. mosquitoes were collected using pyrethrum spray catch method from two ecological zones of Mauritania: Nouakchott (Saharan zone) and Hodh Elgharbi region (Sahelian zone). Circumsporozoite proteins (CSP) for P. falciparum, P. vivax VK210 and P. vivax VK247 were detected by enzyme-linked immunosorbent assay (ELISA) from the female anopheline mosquitoes. To confirm CSP-ELISA results, polymerase chain reaction (PCR) was also performed. Blood meal identification was performed in all engorged females by partial sequencing of the mitochondrial cytochrome b gene. Molecular assessments of pyrethroid knockdown resistance (kdr) and insensitive acetylcholinesterase resistance (ace-1) were conducted.

Results

In Nouakchott, the only species of Anopheles identified during the survey was Anopheles arabiensis (356 specimens). In Hodh Elgharbi, 1016 specimens of Anopheles were collected, including 578 (56.9 %) Anopheles rufipes, 410 (40.35 %) An. arabiensis, 20 (1.96 %) An. gambiae, 5 (0.5 %) An. pharoensis and 3 (0.3 %) An. funestus. Three of 186 female An. arabiensis collected in Nouakchott and tested by ELISA were found positive for Plasmodium vivax VK210, corresponding to a sporozoite rate of 1.6 %; however PCR confirmed infection by P. vivax sporozoite in only one of these. In Hodh Elgharbi, no mosquito was found positive for Plasmodium spp. infection. There was a statistically significant difference in the percentage of human blood-fed Anopheles spp. between Nouakchott (58.7 %, 47 of 80 blood-engorged An. arabiensis females) and Hodh Elgharbi (11.1 %, 2 of 18 blood-engorged mosquitoes). Analysis of the kdr polymorphisms showed 48.2 % (70/145) of East African kdr mutation (L1014S) in Nouakchott compared to 10 % (4/40) in Hodh Elgharbi region (P < 0.001). Nevertheless, West African kdr mutation (L1014F) was found only in An. gambiae populations (4/40, 10 %) from Hodh Elgharbi region. No ace-1 mutation was found in mosquito specimens from the two study zones.

Conclusions

Overall, this study confirmed the autochthonous P. vivax malaria transmission in Nouakchott, involving An. arabiensis as the main vector. It also described for the first time the absence of ace-1 mutation, the co-occurrence of both West and East African kdr mutation in An. gambiae in Mauritania, and highlighted the regional variations in the prevalence and type of kdr mutations.

Malaria in three epidemiological strata in Mauritania

Background

Malaria epidemiology in Mauritania has been characterized on the basis of epidemiological strata, defined by climatic and geographic features, which divide the country into three zones: Sahelian zone, Sahelo-Saharan transition zone, and Saharan zone. The association between geographic stratification and malaria transmission was assessed through a series of parasitological and entomological surveys.

Methods

Surveys were conducted during the ‘cool’ dry season in 2011, ‘hot’ dry season in 2012, and rainy season in 2013 in a total of 12 sentinel sites. Finger-prick capillary blood samples were collected from children aged 2–9 years old in randomly selected households for microscopic examination and rapid diagnostic test for malaria. Adult mosquitoes were sampled by pyrethrum spray catch and CDC light traps and identified using morphological keys and molecular tools.

Results

Of 3445 children included, 143 (4.15 %) were infected with malaria parasites including Plasmodium falciparum (n = 71, 2.06 %), Plasmodium vivax (57, 1.65 %), P. falciparum-P. vivax (2, 0.06 %), Plasmodium ovale (12, 0.35 %), and Plasmodium malariae (1, 0.03 %). A large majority of P. falciparum infections were observed in the Sahelo-Saharan zone. Malaria prevalence (P < 0.01) and parasite density (P < 0.001) were higher during the rainy season (2013), compared to cool dry season (2011). Plasmodium vivax was mainly observed in the Saharan region [43 of 59 (73 %) P. vivax infections], mostly in Nouakchott districts, with no significant seasonal variation. Of 3577 mosquitoes captured, 1014 (28.3 %) belonged to Anopheles spp. Anopheles gambiae was the predominant species in all three epidemiological strata during the ‘cool’ dry season in 2011 but was absent in all study sites, except for Teyarett district in Nouakchott, during the ‘hot’ dry season in 2012. During the rainy season in 2013, An. gambiae, Anopheles arabiensis, Anopheles pharoensis, and Anopheles rufipes were abundant in different zones.

Conclusions

The results of the present study support the stratification of malaria in Mauritania. However, the Sahelian zone had the lowest malaria prevalence, while the Sahelo-Saharan zone had the highest malaria burden. Local changes due to anthropogenic factors (i.e., human migration, urbanization, malaria interventions) should be considered in order to optimize the control strategy.

Malaria burden and anti-malarial drug efficacy in Owando, northern Congo

Background

In the Republic of Congo, previous epidemiological studies have only been conducted in the south of the country where it is most accessible. Nationally representative data on the efficacy of new anti-malarial tools are lacking in the country. As an initial step to close the gap, clinical efficacy of two artemisinin-based combinations, artesunate-amodiaquine (ASAQ) and artemether-lumefantrine (AL), was assessed in Owando, a city in equatorial flooded forest in northern Republic of Congo.

Methods

Under 12 years old febrile children attending public health facilities were screened for malaria parasites using lactate dehydrogenase (LDH)-based rapid diagnostic test (RDT) for malaria and microscopic examination of thick blood films. Patients with at least 1,000 asexual Plasmodium falciparum parasites/µl of blood were clinically examined, included after informed consent, and followed up for 28 days, according to the 2009 World Health Organization protocol. Patients were randomly assigned to co-formulated ASAQ (Coarsucam^®) or AL (Coartem^®) treatment groups. Plasmodium falciparum recrudescent isolates were compared to pre-treatment isolates by polymerase chain reaction (PCR) using msp1, msp2, and glurp genes to distinguish between re-infection and recrudescence.

Results

Between November 2012 and February 2013, 857 under 12 years old febrile children were screened, of whom 198 (23.1 %) had positive RDT and 167 (19.5 %) positive thick films. ASAQ and AL efficacies were 92.7 and 94.2 % before PCR correction, respectively. After genotyping, the overall efficacy was 100 % for ASAQ and 98.0 % for AL.

Conclusion

The data reported here represent partially the burden of malaria in 0–11 years old febrile children examined in public health centres of Owando city and serve as reference for further studies. Both artemisinin-based combinations were highly efficacious in patients under 12 years old with acute uncomplicated malaria. ASAQ was associated with more adverse events, which may reduce compliance in unsupervised treatment.

Trial registration: ACTRN12612000940875

Polymorphism of the merozoite surface protein-1 block 2 region in Plasmodium falciparum isolates from Mauritania

BACKGROUND

The genetic diversity of Plasmodium falciparum has been extensively studied in various parts of the world. However, limited data are available from Mauritania. The present study examined and compared the genetic diversity of P. falciparum isolates in Mauritania.

METHODS

Plasmodium falciparum isolates blood samples were collected from 113 patients attending health facilities in Nouakchott and Hodh El Gharbi regions. K1, Mad20 and RO33 allelic family of msp-1 gene were determined by nested PCR amplification.

RESULTS

K1 family was the predominant allelic type carried alone or in association with Ro33 and Mad20 types (90%; 102/113). Out of the 113 P. falciparum samples, 93(82.3%) harboured more than one parasite genotype. The overall multiplicity of infection was 3.2 genotypes per infection. There was no significant correlation between multiplicity of infection and age of patients. A significant increase of multiplicity of infection was correlated with parasite densities.

CONCLUSIONS

The polymorphism of P. falciparum populations from Mauritania was high. Infection with multiple P. falciparum clones was observed, as well as a high multiplicity of infection reflecting both the high endemicity level and malaria transmission in Mauritania.

Emergence of Plasmodium ovale malaria among the French Armed Forces in the Republic of Ivory Coast: 20 years of clinical and biological experience

BACKGROUND

French military surveillance identified an increase in Plasmodium ovale attacks among soldiers in Ivory Coast. This emergence and the low sensitivity of biological tests raise the question of a possible role of P. ovale variant species.

METHODS

Epidemiological data about P. ovale attacks from 1993 to 2012 were studied; the species diagnosis was based on a thin blood smear and/or a quick diagnostic test. Clinical and biological features in soldiers hospitalized in 2 French military hospitals were also reviewed. Malaria polymerase chain reaction followed by genotyping was performed when available.

RESULTS

French military physicians declared 328 P. ovale attacks over the 20-year study. A peak of incidence occurred in 2005. Among patients with positive blood smears, the quick diagnostic test was positive in 33 of 101 tests performed. The hospital study showed that symptoms and biological changes were not specific, which made diagnosis challenging: fever, anemia, and thrombocytopenia were not present in 20%, 71%, and 23% of the 45 confirmed cases, respectively. It was possible to perform molecular investigations on 19 clinical isolates: 18 were classic haplotypes with additional polymorphism and 1 was variant.

CONCLUSIONS

This emergence of P. ovale malaria enabled a good description to be made in nonimmune patients. The lack of sensitivity of both clinical features and quick diagnostic tests suggests an underestimation. Reasons for this outbreak are especially intense exposure to the vectors and the insufficient efficacy of doxycycline against P. ovale. The polymorphism of classic haplotypes of P. ovale rather than variant forms could be involved.

Population genetics analysis during the elimination process of Plasmodium falciparum in Djibouti

Background

Case management of imported malaria within the context of malaria pre-elimination is increasingly considered to be relevant because of the risk of resurgence. The assessment of malaria importation would provide key data i) to select countries with propitious conditions for pre-elimination phase and ii) to predict its feasibility. Recently, a sero-prevalence study in Djibouti indicated low malaria prevalence, which is propitious for the implementation of pre-elimination, but data on the extent of malaria importation remain unknown.

Methods

Djiboutian plasmodial populations were analysed over an eleven-year period (1998, 1999, 2002 and 2009). The risk of malaria importation was indirectly assessed by using plasmodial population parameters. Based on 5 microsatellite markers, expected heterozygosity (H.e.), multiplicity of infection, pairwise Fst index, multiple correspondence analysis and individual genetic relationship were determined. The prevalence of single nucleotide polymorphisms associated with pyrimethamine resistance was also determined.

Results

Data indicated a significant decline in genetic diversity (0.51, 0.59, 0.51 and 0 in 1998, 1999, 2002 and 2009, respectively) over the study period, which is inconsistent with the level of malaria importation described in a previous study. This suggested that Djiboutian malaria situation may have benefited from the decline of malaria prevalence that occurred in neighbouring countries, in particular in Ethiopia. The high Fst indices derived from plasmodial populations from one study period to another (0.12 between 1999 and 2002, and 0.43 between 2002 and 2009) suggested a random sampling of parasites, probably imported from neighbouring countries, leading to oligo-clonal expansion of few different strains during each transmission season. Nevertheless, similar genotypes observed during the study period suggested recurrent migrations and imported malaria.

Conclusion

In the present study, the extent of genetic diversity was used to assess the risk of malaria importation in the low malaria transmission setting of Djibouti. The molecular approach highlights i) the evolution of Djiboutian plasmodial population profiles that are consistent and compatible with Djiboutian pre-elimination goals and ii) the necessity to implement the monitoring of plasmodial populations and interventions at the regional scale in the Horn of Africa to ensure higher efficiency of malaria control and elimination.

In vitro susceptibility to quinine and microsatellite variations of the Plasmodium falciparum Na+/H+ exchanger transporter (Pfnhe-1) gene in 393 isolates from Dakar, Senegal

Background

Although the World Health Organization recommends replacing quinine (QN) by artesunate due to its increased efficacy and the higher tolerance to the drug in both adults and children, QN remains a first-line treatment for severe malaria, especially in Africa. Investigations of microsatellite Pfnhe-1 ms4760 polymorphisms in culture-adapted isolates from around the world have revealed that an increase in the number of DNNND amino acid motifs was associated with decreased QN susceptibility, whereas an increase in the number of DDNHNDNHNND motifs was associated with increased QN susceptibility.

Methods

In this context, to further analyse associations between Pfnhe-1 ms4760 polymorphisms and QN susceptibility, 393 isolates freshly collected between October 2009 and January 2010 and July 2010 and February 2011, respectively, at the Hôpital Principal de Dakar, Senegal were assessed ex vivo for QN susceptibility, and their genes were amplified and sequenced.

Results

Of the 393 Plasmodium falciparum clinical isolates collected, 145 were successfully cultured. The 145 QN IC₅₀s ranged from 2.1 to 1291 nM, and 17 isolates (11.7%) exceed the QN reduced susceptibility threshold of 611 nM. Among the 393 P. falciparum clinical isolates, 47 different alleles were observed. The three most prevalent profiles were ms4760-1 (no = 72; 18.3%), ms4760-3 (no = 65; 16.5%) and ms4760-7 (no = 40; 10.2%). There were no significant associations observed between QN IC₅₀ values and i) the number of repeats of DNNND in block II (p = 0.0955, Kruskal-Wallis test); ii) the number of repeats of DDNHNDNHNND in block V (p = 0.1455, Kruskal-Wallis test); or iii) ms4760 profiles (p = 0.1809, Kruskal-Wallis test).

Conclusions

Pfnhe-1 ms4760 was highly diverse in parasite isolates from Dakar (47 different profiles). Three profiles (ms4760-1, ms4760-3 and ms4760-7) were predominant. The number of repeats for block II (DNNND) or block V (DDNHNDNHNND) was not significantly associated with QN susceptibility. New studies, and especially in vivo studies, are necessary to confirm the role of Pfnhe-1 ms4760 as a marker of QN resistance.

Plasmodium vivax and Plasmodium falciparum infections in the Republic of Djibouti: evaluation of their prevalence and potential determinants

Background

Formerly known as a hypoendemic malaria country, the Republic of Djibouti declared the goal of pre-eliminating malaria in 2006. The aim of the present study was to evaluate the prevalence of Plasmodium falciparum, Plasmodium vivax and mixed infections in the Djiboutian population by using serological tools and to identify potential determinants of the disease and hotspots of malaria transmission within the country.

Methods

The prevalence of P. falciparum and P. vivax within the districts of the capital city and the rest of the Republic of Djibouti were assessed using 13 and 2 serological markers, respectively. The relationship between the immune humeral response to P. falciparum and P. vivax and variables such as age, gender, wealth status, urbanism, educational level, distance to rivers/lakes, living area, having fever in the last month, and staying in a malaria-endemic country more than one year was estimated and analysed by questionnaires administered to 1910 Djiboutians. Multivariate ordinal logistic regression models of the immune humeral response were obtained for P. falciparum and P. vivax.

Results

The P. falciparum and P. vivax seroprevalence rates were 31.5%, CI95% [29.4-33.7] and 17.5%, CI95% [15.8-19.3], respectively. Protective effects against P. falciparum and P. vivax were female gender, educational level, and never having visited a malaria-endemic area for more than one year. For P. falciparum only, a protective effect was observed for not having a fever in the last month, living more than 1.5 km away from lakes and rivers, and younger ages.

Conclusions

This is the first study that assessed the seroprevalence of P. vivax in the Republic of Djibouti. It is necessary to improve knowledge of this pathogen in order to create an effective elimination programme. As supported by recent observations on the subject, the Republic of Djibouti has probably demonstrated a real decrease in the transmission of P. falciparum in the past seven years, which should encourage authorities to improve efforts toward elimination.

Multiple independent introductions of Plasmodium falciparum in South America

The origin of Plasmodium falciparum in South America is controversial. Some studies suggest a recent introduction during the European colonizations and the transatlantic slave trade. Other evidence--archeological and genetic--suggests a much older origin. We collected and analyzed P. falciparum isolates from different regions of the world, encompassing the distribution range of the parasite, including populations from sub-Saharan Africa, the Middle East, Southeast Asia, and South America. Analyses of microsatellite and SNP polymorphisms show that the populations of P. falciparum in South America are subdivided in two main genetic clusters (northern and southern). Phylogenetic analyses, as well as Approximate Bayesian Computation methods suggest independent introductions of the two clusters from African sources. Our estimates of divergence time between the South American populations and their likely sources favor a likely introduction from Africa during the transatlantic slave trade.

Molecular surveillance of drug-resistant Plasmodium vivax using pvdhfr, pvdhps and pvmdr1 markers in Nouakchott, Mauritania

OBJECTIVES

Plasmodium falciparum and Plasmodium vivax occur in Mauritania. Drug-resistant P. falciparum has been reported, but the drug-resistance status of P. vivax is unknown. The aims of the present study were to determine the prevalence of mutant pvdhfr, pvdhps and pvmdr1 genes and of pvmdr1 gene amplification in P. vivax isolates in Nouakchott, the capital city of Mauritania, and to establish a baseline for molecular surveillance of drug-resistant P. vivax in the country.

PATIENTS AND METHODS

Between 2007 and 2009, 439 febrile patients were screened for malaria in Nouakchott. The sequences of pvdhfr, pvdhps and pvmdr1 markers in 110 P. vivax isolates were determined by direct sequencing of PCR products. The pvmdr1 gene copy number was determined by real-time PCR.

RESULTS

The majority of the isolates with a successful PCR amplification (76/86, 88%) were characterized to be of the wild-type pvdhfr genotype, while the remaining 10 isolates carried the S58R and S117N double mutations. All isolates had the wild-type pvdhps genotype SAKAV. For pvmdr1, 75 of 103 (73%) had the wild-type Y976, and 28 (27%) carried the mutant F976. Most (98%) carried the mutant L1076 codon. Of 105 isolates, 102 (97%) had one copy and 3 (3%) had two copies of the pvmdr1 gene.

CONCLUSIONS

The prevalence of mutations associated with antifolate resistance is low in Mauritania. Further studies are required to determine the roles of pvmdr1 mutations and gene amplification in conferring drug resistance. These data will serve as a baseline for further monitoring of drug-resistant malaria.

Vivax malaria in Mauritania includes infection of a Duffy-negative individual

Background

Duffy blood group polymorphisms are important in areas where Plasmodium vivax is present because this surface antigen is thought to act as a key receptor for this parasite. In the present study, Duffy blood group genotyping was performed in febrile uninfected and P. vivax-infected patients living in the city of Nouakchott, Mauritania.

Methods

Plasmodium vivax was identified by real-time PCR. The Duffy blood group genotypes were determined by standard PCR followed by sequencing of the promoter region and exon 2 of the Duffy gene in 277 febrile individuals. Fisher's exact test was performed in order to assess the significance of variables.

Results

In the Moorish population, a high frequency of the FYB^ES/FYB^ES genotype was observed in uninfected individuals (27.8%), whereas no P. vivax-infected patient had this genotype. This was followed by a high level of FYA/FYB, FYB/FYB, FYB/FYB^ES and FYA/FYB^ES genotype frequencies, both in the P. vivax-infected and uninfected patients. In other ethnic groups (Poular, Soninke, Wolof), only the FYB^ES/FYB^ES genotype was found in uninfected patients, whereas the FYA/FYB^ES genotype was observed in two P. vivax-infected patients. In addition, one patient belonging to the Wolof ethnic group presented the FYB^ES/FYB^ES genotype and was infected by P. vivax.

Conclusions

This study presents the Duffy blood group polymorphisms in Nouakchott City and demonstrates that in Mauritania, P. vivax is able to infect Duffy-negative patients. Further studies are necessary to identify the process that enables this Duffy-independent P. vivax invasion of human red blood cells.

Malaria prevalence and morbidity among children reporting at health facilities in Nouakchott, Mauritania

Although malaria has become a serious public health problem in Mauritania since the late 1990s, few documented data on its epidemiology exist. The objective of this study was to assess the morbidity of clinical malaria among children in Nouakchott. Three hundred and one febrile children, consulting at three health facilities of Nouakchott, were screened for malaria in 2009 (n=216) and 2010 (n=85). Plasmodium species identification and parasite density were determined by microscopic examination of Giemsa-stained thin and thick films and confirmed by rapid diagnostic test and nested PCR. Of 301 febrile children, 105 (34.9%) were malaria-positive by nested PCR and 87 (28.9%) by microscopy. Plasmodium vivax represented 97.1% (102/105) and P. falciparum accounted for 2.9% (3/105) of positive cases. All positive children under five years old were infected with P. vivax. The highest numbers of malaria positives were found during or shortly after the rainy season and the lowest during the dry season. Fifty-four of 105 (51.4%) malaria cases, all with P. vivax, had never travelled outside Nouakchott. Individuals belonging to the Moors ethnic group represented 97.0% of P. vivax cases. Results of the present study indicate that malaria is endemic in Nouakchott and that P. vivax is the principal causative agent. Regular surveillance is required to monitor malaria prevalence and incidence, and further measures are needed to counter the possible spread of malaria in the country.

Unusual transmission of Plasmodium falciparum, Bordeaux, France, 2009

Plasmodium falciparum malaria is usually transmitted by mosquitoes. We report 2 cases in France transmitted by other modes: occupational blood exposure and blood transfusion. Even where malaria is not endemic, it should be considered as a cause of unexplained acute fever.

Genetic structure of Plasmodium falciparum and elimination of malaria, Comoros archipelago

Elimination interventions should be implemented simultaneously throughout the entire archipelago.

The efficacy of malaria control and elimination on islands may depend on the intensity of new parasite inflow. On the Comoros archipelago, where falciparum malaria remains a major public health problem because of spread of drug resistance and insufficient malaria control, recent interventions for malaria elimination were planned on Moheli, 1 of 4 islands in the Comoros archipelago. To assess the relevance of such a local strategy, we performed a population genetics analysis by using multilocus microsatellite and resistance genotyping of Plasmodium falciparum sampled from each island of the archipelago. We found a contrasted population genetic structure explained by geographic isolation, human migration, malaria transmission, and drug selective pressure. Our findings suggest that malaria elimination interventions should be implemented simultaneously on the entire archipelago rather than restricted to 1 island and demonstrate the necessity for specific chemoresistance surveillance on each of the 4 Comorian islands.

In vitro susceptibility to quinine and microsatellite variations of the Plasmodium falciparum Na+/H+ exchanger (Pfnhe-1) gene: the absence of association in clinical isolates from the Republic of Congo

Background

Quinine is still recommended as an effective therapy for severe cases of Plasmodium falciparum malaria, but the parasite has developed resistance to the drug in some cases. Investigations into the genetic basis for quinine resistance (QNR) suggest that QNR is complex and involves several genes, with either an additive or a pairwise effect. The results obtained when assessing one of these genes, the plasmodial Na⁺/H⁺ exchanger, Pfnhe-1, were found to depend upon the geographic origin of the parasite strain. Most of the associations identified have been made in Asian strains; in contrast, in African strains, the influence of Pfnhe on QNR is not apparent. However, a recent study carried out in Kenya did show a significant association between a Pfnhe polymorphism and QNR. As genetic differences may exist across the African continent, more field data are needed to determine if this association exists in other African regions. In the present study, association between Pfnhe and QNR is investigated in a series of isolates from central Africa.

Methods

The sequence analysis of the polymorphisms at the Pfnhe-1 ms4760 microsatellite and the evaluation of in vitro quinine susceptibility (by isotopic assay) were conducted in 74 P. falciparum isolates from the Republic of Congo.

Results

Polymorphisms in the number of DNNND or NHNDNHNNDDD repeats in the Pfnhe-1 ms4760 microsatellite were not associated with quinine susceptibility.

Conclusions

The polymorphism in the microsatellite ms4760 in Pfnhe-1 that cannot be used to monitor quinine response in the regions of the Republic of Congo, where the isolates came from. This finding suggests that there exists a genetic background associated with geographic area for the association that will prevent the use of Pfnhe as a molecular marker for QNR. The contribution of Pfnhe to the in vitro response to quinine remains to be assessed in other regions, including in countries with different levels of drug pressure.

Population genetic structure of Anopheles gambiae and Anopheles arabiensis in Niger

The increasing usage of long-lasting insecticide-treated nets allows protection of millions of people from malaria infection. Monitoring studies should be planned during any wide-scale malaria control program integrating insecticide-treated materials, to evaluate their effects and effectiveness on epidemiologically relevant parameters. Such operational control interventions may be challenged by insecticide resistance spread within vector populations, as a result of wide insecticide pressure. A nationwide distribution of long-lasting insecticidal nets was implemented throughout Niger in 2005. We studied the population genetic structure of major malaria vectors across Nigerien Sahel, and investigated potential effects of this large malaria control intervention. Wild-caught Anopheles gambiae sensu lato females from seven villages and two wet seasons were genotyped at 12 microsatellite loci. The genetic diversity within both species appeared homogenous between villages and years. The estimated genetic differentiation among samples was very low within both species, indicating high gene flow across the area. An absence of differentiation was also found between 2005 and 2006 wet seasons, for all samples but one, showing that the net distribution did not impact significantly the genetic diversity and structure of vector populations in a single year. We provide valuable results participating to document effects of large malaria control programs, to maximize the efficiency of available tools in future interventions.

[Molecular markers of Plasmodium falciparum drug resistance]

The main Plasmodium falciparum genes known to be associated with drug resistance are pfcrt, pfmdr1, pfdhfr pfdhps, pfcytb, pfmrp, pfnhe1, pfmdt, pfserca and pftetQ. Molecular markers for resistance to chloroquine, amodiaquine, mefloquine, sulfadoxine-pyrimethamine, cycloguanil and atovaquone have been validated and used to predict the parasitological and clinical efficacy of these drugs (i.e. based on in vivo tests). These molecular markers have numerous advantages. They allow evaluation of large series of samples in less time than in vivo tests. Collection, transport and storage of samples are much easier than for in vitro tests. These markers can be used for epidemiological monitoring of resistance for an entire country as well as for prediction of therapeutic outcome for a single individual. Development of high-throughput molecular biology techniques, availability of the nucleotidic sequences of P. falciparum genomes, and close collaboration between fundamental researcher workers, clinical practitioners, and officials in charge of the national malaria control programs are major assets in the research and development of molecular markers for P. falciparum resistance to antimalarial drugs.

[Distinguishing Plasmodium falciparum populations for clinical research]

The genetic diversity of Plasmodium falciparum is generally high. Study of this diversity is useful to differentiate the strains present in an individual before and after malaria treatment or to check if several individuals have been infected by the same parasites. Interpretation of the in vivo test recommended by the WHO to evaluate antimalarial drug efficacy requires distinguishing recrudescence from new infection when recurrent parasitemia suggests the possibility of therapeutic failure and antimalaria resistance. For this purpose, molecular biology techniques such as nested-PCRs are becoming increasingly available and can now be used in most endemic areas. An effort has been made to standardize P. falciparum genotyping carried out to distinguish recrudescence from new infection. Standardization has focused not only on genotyping methods but also on interpretation criteria. Compliance with these recommendations should improve the quality of clinical research and allow comparison of data from different centers.

Atypical aetiology of a conjugal fever: autochthonous airport malaria between Paris and French Riviera: a case report

Endemic malaria has been eradicated from France, but some falciparum malaria cases have been described in patients who have never travelled outside the country. Ms. V. 21 year-old and Mr. M. 23 year-old living together in Paris were on holiday in Saint Raphaël (French Riviera). They presented with fever, vertigo and nausea. A blood smear made to control thrombocytopaenia revealed intra-erythrocytic forms of Plasmodium falciparum. The parasitaemia level was 0.15% for Ms. V and 3.2% for Mr. M. This couple had no history of blood transfusion or intravenous drug use. They had never travelled outside metropolitan France, but had recently travelled around France: to Saint Mard (close to Paris Charles de Gaulle (CdG) airport), to Barneville plage (in Normandy) and finally to Saint Raphaël. The most probable hypothesis is an infection transmitted in Saint Mard by an imported anopheline mosquito at CdG airport. The DNA analysis of parasites from Ms. V.'s and Mr. M.'s blood revealed identical genotypes. Because it is unlikely that two different anopheline mosquitoes would be infected by exactly the same clones, the two infections must have been caused by the infective bites of the same infected mosquito.

Antimalarial drug use in general populations of tropical Africa

Background

The burden of Plasmodium falciparum malaria has worsened because of the emergence of chloroquine resistance. Antimalarial drug use and drug pressure are critical factors contributing to the selection and spread of resistance. The present study explores the geographical, socio-economic and behavioural factors associated with the use of antimalarial drugs in Africa.

Methods

The presence of chloroquine (CQ), pyrimethamine (PYR) and other antimalarial drugs has been evaluated by immuno-capture and high-performance liquid chromatography in the urine samples of 3,052 children (2–9 y), randomly drawn in 2003 from the general populations at 30 sites in Senegal (10), Burkina-Faso (10) and Cameroon (10). Questionnaires have been administered to the parents of sampled children and to a random sample of households in each site. The presence of CQ in urine was analysed as dependent variable according to individual and site characteristics using a random – effect logistic regression model to take into account the interdependency of observations made within the same site.

Results

According to the sites, the prevalence rates of CQ and PYR ranged from 9% to 91% and from 0% to 21%, respectively. In multivariate analysis, the presence of CQ in urine was significantly associated with a history of fever during the three days preceding urine sampling (OR = 1.22, p = 0.043), socio-economic level of the population of the sites (OR = 2.74, p = 0.029), age (2–5 y = reference level; 6–9 y OR = 0.76, p = 0.002), prevalence of anti-circumsporozoite protein (CSP) antibodies (low prevalence: reference level; intermediate level OR = 2.47, p = 0.023), proportion of inhabitants who lived in another site one year before (OR = 2.53, p = 0.003), and duration to reach the nearest tarmacked road (duration less than one hour = reference level, duration equal to or more than one hour OR = 0.49, p = 0.019).

Conclusion

Antimalarial drug pressure varied considerably from one site to another. It was significantly higher in areas with intermediate malaria transmission level and in the most accessible sites. Thus, P. falciparum strains arriving in cross-road sites or in areas with intermediate malaria transmission are exposed to higher drug pressure, which could favour the selection and the spread of drug resistance.

Possible autochthonous malaria from Marseille to Minneapolis

We report 2 cases of Plasmodium falciparum malaria in southern France in a French woman and an American man of Togolese origin who reported no recent travel to malaria-endemic countries. Both infections occurred after a stay near Marseille, which raises the possibility of autochthonous transmission. Entomologic and genotypic investigations are described.

[Proteomic analysis and parasitosis: principles and applications]

O'Farrel described a method allowing two-dimensional (2D) protein separation more than 30 years ago. Since then the original technique has made enormous progress. This progress has been accompanied by advances in mass spectrometry technology as well as various genome-sequencing programs. Today 2D electrophoresis has become the workhorse of proteomics, allowing resolution of complex structures containing thousands of proteins and providing a global view of the state of a proteome. This article presents the different steps and limitations of proteomic analysis: preparation of biological material, 2D electrophoresis, protein detection systems, and available tools for protein identification. Alternative proteomic approaches to 2D electrophoresis are also presented. A few applications are described as examples to illustrate the utility of proteomic analysis for studying the mechanisms underlying virulence, resistance to antimalarial therapies and immune response against pathologic agents.

Chloroquine Resistance Reversal Agents as Promising Antimalarial Drugs

The development and spread of resistance to antimalarial drugs poses a severe and increasing public health threat. Failures of prophylaxis or treatment with quinolines, hydroxynaphthoquinones, sesquiterpene lactones, antifolate drugs and sulfamides are involved in a return malaria-related morbidity and mortality. Resistance is associated with a decrease in accumulation of drugs into the vacuole, which results from a reduced uptake of the drug, an increased efflux or a combination of both. A number of candidate genes in P. falciparum have been proposed to be involved in antimalarial resistance, each concerned in membrane transport. Weaker or stronger associations are seen in P. falciparum between the resistance to quinolines or artemisinin derivatives and codon changes in Pfmdr1, a gene which encodes Pgh-1, an ortholog of one of the P-glycoproteins expressed in multi-drug resistant human cancer cells (ABC transporter). Further analysis has revealed a new gene, Pfcrt, encoding a PfCRT protein, which resembles an anion channel. Codon changes found in the Pfcrt sequence in drug resistant isolates could facilitate the drug efflux through a putative channel. It has been proposed that the reversal of quinoline resistance by verapamil is due to hydrophobic binding to the mutated PfCRT protein. Several compounds have demonstrated in the past decade a promising capability to reverse the antimalarial drug resistance in vitro in parasite isolates, in animal models and in human malaria. These drugs belong to different pharmacological classes such as calcium channel blockers, tricyclic antidepressants, antipsychotic calmodulin antagonists, histamine H1-receptor antagonists, analgesic and antipyretic drugs, non-steroidal anti-inflammatory drugs, and to different chemical classes such as synthetic surfactants, alkaloids from plants used in traditional medicine, pyrrolidinoaminoalkanes and anthracenic derivatives. Here we summarize the progress made in biochemical and genetic basis of antimalarial resistance, emphasizing the recent developments on drugs, which interfere with trans membrane proteins involved in drug efflux or uptake.

Genetic diversity and structure of African Plasmodium falciparum populations in urban and rural areas

The genetic variability and population structure of Plasmodium falciparum are key factors in malaria control strategies. Studies have suggested no P. falciparum population structure although linkage disequilibrium was observed in some African areas. We have assessed length polymorphism at 6-22 microsatellites in four urban and rural sites (Djibouti, Dakar, Niamey, and Zouan-Hounien, n = 240 blood samples). Results have shown a P. falciparum population structure in Africa (Fst = 0.17-0.24), lower genetic diversity in Djibouti (He = 0.53) than in the other sites (He = 0.73-0.76), and 3) significant linkage disequilibrium in Djibouti. These results could be related to geographic isolation and low flow of parasites between sites. They also suggest a potential effect of rural suburbs to generate genetic diversity in towns. This could affect the dispersal of selected drug resistance and should be considered when adapting urban malaria control strategies.

[Metallocenes and malaria: a new therapeutic approach]

Rapid development of significant resistance to antimalarial drugs has been a major force driving research to identify and develop new compounds. The use of synthetic organometallic complexes seems to be promising for treatment of malaria infections. Recent progress in identification and development of new drugs promises to lead to a much greater range of antimalarial agents. Organometallic complexes and metalloporphyrins have shown in vitro activity against Plasmodium falciparum. Ferroquine (ferrocenyl chloroquine) is more active than chloroquine against strains and isolates of P. falciparum and shows efficacy against murine parasites.

Malaria epidemic and drug resistance, Djibouti

Analysis of Plasmodium falciparum isolates collected before, during, and after a 1999 malaria epidemic in Djibouti shows that, despite a high prevalence of resistance to chloroquine, the epidemic cannot be attributed to a sudden increase in drug resistance of local parasite populations.