Seeking research questions from implementers: considerations for leveraging ground actors research needs in the fight against malaria in West Africa.

BACKGROUND: To strengthen the fight against malaria, it is imperative to identify weaknesses and possible solutions in order to improve programmes implementation. This study reports experiences gained from collaboration between decision-makers and researchers from a World Bank project (Malaria and Neglected Tropical Diseases in the Sahel, SM/NTD). The objectives of this paper were to identify bottlenecks in malaria programme implementation as well as related research questions they bring up. METHODS: Questionnaire addressed to National Malaria Control Programme managers and prioritization workshops were used as a medium to identify research questions. The bottlenecks in malaria programme implementation were identified in seven thematic areas namely governance, human resources, drugs, service provision, use of prevention methods, monitoring and evaluation (M and E), and public support or buy-in. The first five priority questions were: (1) compliance with drug doses on the second and third days during the seasonal chemoprevention (SMC) campaigns, (2) the contribution of community-based distributors to the management of severe cases of malaria in children under 5 years, (3) the SMC efficacy, (4) artemisinin-based combination therapy (ACT) tolerance and efficacy according to existing guidelines, and (5) the quality of malaria control at all levels of the health system. RESULTS AND CONCLUSION: This work showed the effectiveness of collaboration between implementers, programmes managers, and researchers in identifying research questions. The responses to these identified research questions of this study may contribute to improving the implementation of malaria control programmes across African countries.

Effectiveness and safety of artemether-lumefantrine versus artesunate-amodiaquine for unsupervised treatment of uncomplicated falciparum malaria in patients of all age groups in Nanoro, Burkina Faso: a randomized open label trial.

BACKGROUND: Several studies have reported high efficacy and safety of artemisinin-based combination therapy (ACT) mostly under strict supervision of drug intake and limited to children less than 5 years of age. Patients over 5 years of age are usually not involved in such studies. Thus, the findings do not fully reflect the reality in the field. This study aimed to assess the effectiveness and safety of ACT in routine treatment of uncomplicated malaria among patients of all age groups in Nanoro, Burkina Faso. METHODS: A randomized open label trial comparing artesunate-amodiaquine (ASAQ) and artemether-lumefantrine (AL) was carried out from September 2010 to October 2012 at two primary health centres (Nanoro and Nazoanga) of Nanoro health district. A total of 680 patients were randomized to receive either ASAQ or AL without any distinction by age. Drug intake was not supervised as pertains in routine practice in the field. Patients or their parents/guardians were advised on the time and mode of administration for the 3 days treatment unobserved at home. Follow-up visits were performed on days 3, 7, 14, 21, and 28 to evaluate clinical and parasitological resolution of their malaria episode as well as adverse events. PCR genotyping of merozoite surface proteins 1 and 2 (msp-1, msp-2) was used to differentiate recrudescence and new infection. RESULTS: By day 28, the PCR corrected adequate clinical and parasitological response was 84.1 and 77.8 % respectively for ASAQ and AL. The cure rate was higher in older patients than in children under 5 years old. The risk of re-infection by day 28 was higher in AL treated patients compared with those receiving ASAQ (p < 0.00001). Both AL and ASAQ treatments were well tolerated. CONCLUSION: This study shows a lowering of the efficacy when drug intake is not directly supervised. This is worrying as both rates are lower than the critical threshold of 90 % required by the WHO to recommend the use of an anti-malarial drug in a treatment policy. TRIAL REGISTRATION: NCT01232530.

[Evaluation of application of national guidelines for the management of malaria in Bobo-Dioulasso university hospital]. / Évaluation de l’application des directives nationales de prise en charge des cas de paludisme au CHU de Bobo-Dioulasso.

INTRODUCTION: To evaluate compliance with national guidelines concerning the diagnosis and treatment of malaria at Souro Sanou university hospital in Bobo-Dioulasso. METHODS: This was a cross-sectional descriptive study based on the medical records of patients hospitalised in the Medicine and Paediatrics departments in 2012. All cases labelled as "malaria" on admission and on discharge, for which the medical records were complete, were included in the study. RESULTS: Of the total of 1,722 cases collected, 1,674 cases (97.22%) were labelled as "severe malaria". The mean age of these patients was 2.65 years [95% CI: 2.41-2.90 years]; 87.63% of cases were under the age of 5 years. The sex-ratio was 1.22. The diagnosis complied with guidelines in 13.82% of cases. The rate of compliance with the diagnosis did not differ according to the severity of the disease (p=0.78), but differed according to age-group: 13.12% in subjects under the age of 5 years versus 18.78% in subjects over the age of 5 years (p=0.02). Cases labelled as "severe malaria" (SM comprised 1.47% of cases of "uncomplicated malaria" (UCM); inversely, 4.17% cases of SM were identified among cases labelled as UCM. Overall, 242 cases (14.05%) were confirmed cases of malaria versus 1,480 cases (85.95%) of presumed malaria. Treatment complied with guidelines in 57.49% of cases. The adequate treatment rate was higher for cases of SM (58.90% versus 8.33%, p<0.01) and in children under the age of 5 years (58.71% versus 48.30%, p=0.02). CONCLUSION: This study demonstrated poor compliance with clinical practice guidelines concerning the management of malaria in Bobo-Dioulasso university hospital. Identification of factors responsible for poor compliance with these guidelines may help to identify appropriate measures to improve compliance and contribute to control of malaria in the country.

Effectiveness of artesunate-amodiaquine vs. artemether-lumefantrine for the treatment of uncomplicated falciparum malaria in Nanoro, Burkina Faso: a non-inferiority randomised trial.

OBJECTIVES: Artemisinin-based combination therapies (ACTs) are essential for the effective control of falciparum malaria in endemic countries. However, in most countries, such choice has been carried out without knowing their effectiveness when deployed in real-life conditions, that is, when treatment is not directly observed. We report here the results of a study assessing the effectiveness of the two ACTs currently recommended in Burkina Faso for the treatment of uncomplicated malaria, that is, artemether-lumefantrine (AL) and artesunate-amodiaquine (ASAQ). METHODS: Between September 2008 and January 2010, 340 children were randomised to one of the two study arms and followed up for 42 days. Treatment was administered according to routine practices, that is, the first dose was given by study nurses who explained to the parent/guardian how to administer the other doses at home during the following 2 days. RESULTS: The results showed a significantly higher unadjusted adequate clinical and parasitological response in the ASAQ (58.4%) than in the AL arm (46.1%) at day 28 but these trends were similar after correction with PCR data (ASAQ (89.7%) and AL (89.8%)). New infections started to appear after day 14, first in the AL and then in the ASAQ arm but at day 42 day of follow-up we observed no difference in the occurrence of recrudescent infection. CONCLUSION: Despite a lower cure rate than those reported in efficacy studies in which the treatment administration was directly observed, both AL and ASAQ can still be used for the treatment of uncomplicated malaria in Burkina Faso.

Ex vivo anti-malarial drugs sensitivity profile of Plasmodium falciparum field isolates from Burkina Faso five years after the national policy change.

BACKGROUND: The recent reports on the decreasing susceptibility of Plasmodium falciparum to artemisinin derivatives along the Thailand and Myanmar border are worrying. Indeed it may spread to India and then Africa, repeating the same pattern observed for chloroquine resistance. Therefore, it is essential to start monitoring P. falciparum sensitivity to artemisinin derivatives and its partner drugs in Africa. Efficacy of AL and ASAQ were tested by carrying out an in vivo drug efficacy test, with an ex vivo study against six anti-malarial drugs nested into it. Results of the latter are reported here. METHODS: Plasmodium falciparum ex-vivo susceptibility to chloroquine (CQ), quinine (Q), lumefantrine (Lum), monodesethylamodiaquine (MDA), piperaquine (PPQ) and dihydroartemisinin (DHA) was investigated in children (6 months - 15 years) with a parasitaemia of at least ≥4,000/µl. The modified isotopic microtest technique was used. The results of cellular proliferation were analysed using ICEstimator software to determine the 50% inhibitory concentration (IC50) values. RESULTS: DHA was the most potent among the 6 drugs tested, with IC50 values ranging from 0.8 nM to 0.9 nM (Geometric mean IC50 = 0.8 nM; 95% CI [0.8 - 0.9]). High IC50 values ranged between 0.8 nM to 166.1 nM were reported for lumefantrine (Geometric mean IC50 = 25.1 nM; 95% CI [22.4 - 28.2]). MDA and Q IC50s were significantly higher in CQ-resistant than in CQ-sensitive isolates (P = 0.0001). However, the opposite occurred for Lum and DHA (P < 0.001). No difference was observed for PPQ. CONCLUSION: Artemisinin derivatives are still very efficacious in Burkina Faso and DHA-PPQ seems a valuable alternative ACT. The high lumefantrine IC50 found in this study is worrying as it may indicate a decreasing efficacy of one of the first-line treatments. This should be further investigated and monitored over time with large in vivo and ex vivo studies that will include also plasma drug measurements.

Plasmodium falciparum Genetic Diversity and Resistance Genotype Profile in Infected Placental Samples Collected After Delivery in Ouagadougou.

Purpose: Intermittent preventive treatment with sulfadoxine-pyrimethamine is widely used for the prevention of malaria in pregnant women in Africa. Known resistance cases of sulfadoxine-pyrimethamine during pregnancy need to be follow up to support IPTp implementation in Burkina Faso. However, data on the development and spread of resistance to this molecule are lacking. This study aimed to investigating the genetic diversity of P. falciparum and the mutation prevalence in the dhfr and dhps genes infected from postpartum infected placentas. Patients and Methods: This was a prospective and cross-sectional study conducted between April 2019 and March 2020 in four health districts of Ouagadougou capital city. From the placentas collected after delivery, P. falciparum detection and mps1 and msp2 polymorphism analysis were performed by nested PCR. The resistance profile was checked after analyzing the mutation point on dhfr and dhps genes. Results: PCR-positive samples were estimated at 96% for msp1 and 98% for msp2. The polymorphism analysis showed that the RO33 and 3D7 allelic families were the most widespread with 62.5% and 91.83%, respectively. Multiple infections by msp1 and msp2 were frequent with 12.50% and 92.92%, respectively. The prevalence of individual dhfr mutation point, 51I, 108A, and 59R, was 1.96, 15.68, and 7.84, respectively, and the dhps mutation point, 437G, was 3.92. There is no detected mutation at the point 164L and 540E. The triple (51I+108A+59R) in dhfr and quadruple (51I+108A+59R+ 437G) mutation were not found. Conclusion: The results showed that Plasmodium falciparum has a high genetic diversity of msp1 and msp2. This suggests that dhfr and dhps mutant genotypes are potential early warning factors in the increase in the sulfadoxine-pyrimethamine resistance.

Prevalence of intestinal parasitic infections among pregnant women in Bobo-Dioulasso (Burkina Faso).

Pregnant women are the most vulnerable populations exposed to intestinal parasitoses. To develop strategies to fight against these infections, it is essential to carry out regular surveys in order to provide reliable epidemiological data on intestinal parasitoses in at-risk populations. A prospective cross-sectional study was carried out from February to April 2015 in pregnant women seen during the prenatal consultation. The study took place in 3 health centers located in Health District of Dafra at Bobo-Dioulasso in Burkina Faso. The parasitological examination consisted in carrying out a standard stool parasitological examination and the modified Ziehl Neelsen staining. A total of 315 stool samples were collected and analyzed. The overall prevalence of intestinal parasitosis was 66.7% [95% CI: 61.1­71.8] with prevalences of 60.9% in Bolomakot., 69.2% in Guimbi and 69.8% in Y.gu.r.sso. Protozoa were the most encountered with of 66.0% prevalence and 1.3% of helminths. The most common protozoa species were Entamoeba coli (36.2%), Giardia lamblia (16.2%), Entamoeba histolytica (14.9%), Cryptosporidium sp. (12.1%) and Trichomonas intestinalis (10.5%). The helminths were represented by Hymenolepis nana (0.6%), Strongyloides stercoralis (0.3%) and Dicrocoelium sp. (0.3%). The prevalence of intestinal parasitosis is very high in pregnant women and dominated by protozoa. Most recently, it has been shown that metronidazole can be administered at all ages of pregnancy at a dosage of 1 g/day for 5 days for the treatment of intestinal protozoa in pregnant women. It would therefore be essential to evaluate this strategy in Burkina Faso by administering metronidazole concomitantly with sulfadoxine-pyrimethamine.

Decreased motivation in the use of insecticide-treated nets in a malaria endemic area in Burkina Faso.

BACKGROUND: The use of insecticide-treated nets (ITN) is an important tool in the Roll Back Malaria (RBM) strategy. For ITNs to be effective they need to be used correctly. Previous studies have shown that many factors, such as wealth, access to health care, education, ethnicity and gender, determine the ownership and use of ITNs. Some studies showed that free distribution and public awareness campaigns increased the rate of use. However, there have been no evaluations of the short- and long-term impact of such motivation campaigns. A study carried out in a malaria endemic area in south-western Burkina Faso indicated that this increased use declined after several months. The reasons were a combination of the community representation of malaria, the perception of the effectiveness and usefulness of ITNs and also the manner in which households are organized by day and by night. METHODS: PermaNet 2.0 and Olyset were distributed in 455 compounds at the beginning of the rainy season. The community was educated on the effectiveness of nets in reducing malaria and on how to use them. To assess motivation, qualitative tools were used: one hundred people were interviewed, two hundred houses were observed directly and two houses were monitored monthly throughout one year. RESULTS: The motivation for the use of bednets decreased after less than a year. Inhabitants' conception of malaria and the inconvenience of using bednets in small houses were the major reasons. Acceptance that ITNs were useful in reducing malaria was moderated by the fact that mosquitoes were considered to be only one of several factors which caused malaria. The appropriate and routine use of ITNs was adversely affected by the functional organization of the houses, which changed as between day and night. Bednets were not used when the perceived benefits of reduction in mosquito nuisance and of malaria were considered not to be worth the inconvenience of daily use. CONCLUSION: In order to bridge the gap between possession and use of bednets, concerted efforts are required to change behaviour by providing accurate information, most particularly by convincing people that mosquitoes are the only source of malaria, whilst recognising that there are other diseases with similar symptoms, caused in other ways. The medical message must underline the seriousness of malaria and the presence of the malaria vector in the dry season as well as the wet, in order to encourage the use of bednets whenever transmission can occur. Communities would benefit from impregnated bednets and other vector control measures being better adapted to their homes, thus reducing the inconvenience of their use.

Genetically diverse Plasmodium falciparum infections, within-host competition and symptomatic malaria in humans.

There is a large genetic diversity of Plasmodium falciparum strains that infect people causing diverse malaria symptoms. This study was carried out to explore the effect of mixed-strain infections and the extent to which some specific P. falciparum variants are associated with particular malaria symptoms. P. falciparum isolates collected during pharmacovigilance study in Nanoro, Burkina Faso were used to determine allelic variation in two polymorphic antigens of the merozoite surface (msp1 and msp2). Overall, parasite density did not increase with additional strains, suggesting the existence of within-host competition. Parasite density was influenced by msp1 allelic families with highest parasitaemia observed in MAD20 allelic family. However, when in mixed infections with allelic family K1, MAD20 could not grow to the same levels as it would alone, suggesting competitive suppression in these mixed infections. Host age was associated with parasite density. Overall, older patients exhibited lower parasite densities than younger patients, but this effect varied with the genetic composition of the isolates for the msp1 gene. There was no effect of msp1 and msp2 allelic family variation on body temperature. Haemoglobin level was influenced by msp2 family with patients harboring the FC27 allele showing lower haemoglobin level than mono-infected individuals by the 3D7 allele. This study provides evidence that P. falciparum genetic diversity influenced the severity of particular malaria symptoms and supports the existence of within-host competition in genetically diverse P. falciparum.

Genotype Analysis of Clinical Candida albicans Isolates Using PCRs Targeting 25S rDNA and ALT Repeat Sequences of the RPS and Antifungal Susceptibility in Ouagadougou (Burkina Faso).

OBJECTIVE: Candida albicans is a yeast with multiple genotypes. It's a commensal fungus colonizing various sites. However, when the host's immune system weakens, it becomes pathogenic and is responsible for various lesions. In Burkina Faso, antifungal drugs are frequently used, particularly fluconazole, the most used systemic antifungal. This antifungal drug and other antifungal drugs are often used for self-medication or prescribed outside of antifungal susceptibility test results. These situations led to the emergence of Candida albicans strains resistant to antifungal drugs commonly used in Burkina Faso. The aim of this study was to determine the types of Candida albicans using PCRs targeting 25S rDNA and ALT repeat sequences of the RPS and to establish their azoles and polyenes susceptibility profile. MATERIAL AND METHODS: Antifungal susceptibility testing by disk diffusion method was performed in accordance with CLSI document M44-A for yeasts and the manufacturer's instructions. Candida albicans isolates were genotyped using specific PCR primers of the rDNA and RPS genes. RESULTS: Ten (10) RPS types of Candida albicans were found in our study: The most common RPS types are A3 (40.6%), A2 (24.0%) and A2/3 (14.6%) for genotype A, B2/3 (5.2%) for genotype B and C2 (3.2%) for genotype C. The Azole resistance, especially fluconazole (74.4%), was the most common with genotype A, including A3 (36.6%), A2 (18. 3%). Polyene resistance was rare with nystatin, only A3 (1.2%) resistant isolate to nystatin was observed. For amphotericin B, the highest observed resistance rates were A3 (11.0%) and A2/3 (8.5%) for the genotype A and B2 (10.0%), B3 (10.0%) and B2/3 (10.0%) for genotype B. CONCLUSION: Our study showed that Candida albicans resistance to azoles, especially to fluconazole, is an important phenomenon in Ouagadougou, and several genotypes RPS types are involved. Thus, fluconazole would not be an antifungal agent for first-line prescribing for treatment of candidiasis in Ouagadougou. This study will be continued to determine the molecular mechanisms involved in these antifungal resistances, for further research of new molecules with different action targets.

Sulfadoxine-pyrimethamine efficacy and selection of Plasmodium falciparum DHFR mutations in Burkina Faso before its introduction as intermittent preventive treatment for pregnant women.

Sulfadoxine-pyrimethamine efficacy was determined with a 28-day follow-up in 97 children between 6 months and 15 years of age. The polymerase chain reaction (PCR)-corrected treatment failure was 8.2% and the uncorrected was 21.6%. The presence of the dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS) mutations linked to sulfadoxine-pyrimethamine resistance before and after treatment was determined by PCR-restriction fragment length polymorphism (RFLP) and by a fluorogenic PCR assay. Before treatment, the prevalence of the triple DHFR mutations was higher among the patients having had a recurrent parasitemia (either recrudescence or new infection; 28.6% versus 9.3%), although the difference was not significant (P = 0.1). The double mutation Ala-436/Gly-437 was observed in 67% of samples, whereas no Glu-540 mutation was found. After treatment, the triple DHFR mutation was found in 76.2% of patients with recurrent parasitemia, recrudescence, and new infection alike. Such high prevalence of mutant parasites indicates that sulfadoxine-pyrimethamine should not be used as monotherapy.

Comparison of effectiveness of two different artemisinin-based combination therapies in an area with high seasonal transmission of malaria in Burkina Faso

In Sahelian countries such as Burkina Faso, malaria transmission is seasonal with a high incidence of transmission during the rainy season. This study aimed to compare the effectiveness of the two recommended treatments (Artemether-Lumefantrine and Artesunate-Amodiaquine) for uncomplicated malaria in Burkina Faso regarding this seasonal variation of malaria transmission. This is part of a randomized open label trial comparing the effectiveness and safety of Artemether-Lumefantrine versus Artesunate-Amodiaquine according to routine practice in Nanoro. Patients with uncomplicated falciparum malaria were recruited all year round and followed-up for 28 days. To distinguish recrudescences from new infections, dried blood spots from day 0 and day of recurrent parasitaemia were used for nested-PCR genotyping of the polymorphic loci of the merozoite surface proteins 1 and 2. Seasonal influence was investigated by assessing the treatment outcomes according to the recruitment period of the patients. Two main groups (dry season versus rainy season) were defined following the seasonal characteristics of the study area. In Artemether-Lumefantrine group, the uncorrected cure rate was 76.5% in dry season versus 37.9% in rainy season. In Artesunate-Amodiaquine group, this was 93.3% and 57.1% during dry and rainy seasons, respectively. After PCR adjustment, the cure rate decreased from 85.9% in dry season to 75.0% in rainy season in Artemether-Lumefantrine group. InA rtesunate-Amodiaquine group, it was 93.3% in dry season and 80.7% during the rainy season. During the rainy season around 50% of patients had a new malaria episode by Day 28. The cure rate of both Artemether-Lumefantrine and Artesunate-Amodiaquine treatments was higher in dry season compared to rainy season due to high incidence of reinfections during the rainy season. For this reason, in addition to the curative effect, the post-treatment prophylactic effect should be taken into account in the choice of antimalarial regimens.

Lessons learnt from 20 years surveillance of malaria drug resistance prior to the policy change in Burkina Faso.

The history of drug resistance to the previous antimalarial drugs, and the potential for resistance to evolve to Artemisinin-based combination therapies, demonstrates the necessity to set-up a good surveillance system in order to provide early warning of the development of resistance. Here we report a review summarizing the history of the surveillance of drug resistance that led to the policy change in Burkina Faso. The first Plasmodium falciparum Chloroquine-Resistance strain identified in Burkina Faso was detected by an in vitro test carried out in Koudougou in 1983. Nevertheless, no further cases were reported until 1987, suggesting that resistant strains had been circulating at a low prevalence before the beginning of the systematic surveillance system from 1984. We observed a marked increase of Chloroquine-Resistance in 2002-2003 probably due to the length of follow-up as the follow-up duration was 7 or 14 days before 2002 and 28 days from 2002 onwards. Therefore, pre-2002 studies have probably under-estimated the real prevalence of Chloroquine-Resistance by not detecting the late recrudescence. With a rate of 8.2% treatment failure reported in 2003, Sulfadoxine-Pyrimethamine was still efficacious for the treatment of uncomplicated malaria in Burkina Faso but this rate might rapidly increase as the result of its spreading from neighboring countries and due to its current use for both the Intermittent Preventive Treatment in pregnant women and Seasonal Malaria Chemoprophylaxis. The current strategy for the surveillance of the Artemisinin-based combination treatments resistance should build on lessons learnt under the previous period of 20 years surveillance of Chloroquine and Sulfadoxine-Pyrimethamine resistance (1994-2004). The most important aspect being to extend the number of sentinel sites so that data would be less patchy and could help understanding the dynamic of the resistance.

Artesunate-Amodiaquine and Artemether-Lumefantrine Therapies and Selection of Pfcrt and Pfmdr1 Alleles in Nanoro, Burkina Faso.

The adoption of Artemisinin based combination therapies (ACT) constitutes a basic strategy for malaria control in sub-Saharan Africa. Moreover, since cases of ACT resistance have been reported in South-East Asia, the need to understand P. falciparum resistance mechanism to ACT has become a global research goal. The selective pressure of ACT and the possibility that some specific Pfcrt and Pfmdr1 alleles are associated with treatment failures was assessed in a clinical trial comparing ASAQ to AL in Nanoro. Dried blood spots collected on Day 0 and on the day of recurrent parasitaemia during the 28-day follow-up were analyzed using the restriction fragments length polymorphism (PCR-RFLP) method to detect single nucleotide polymorphisms (SNPs) in Pfcrt (codon76) and Pfmdr1 (codons 86, 184, 1034, 1042, and 1246) genes. Multivariate analysis of the relationship between the presence of Pfcrt and Pfmdr1 alleles and treatment outcome was performed. AL and ASAQ exerted opposite trends in selecting Pfcrt K76T and Pfmdr1-N86Y alleles, raising the potential beneficial effect of using diverse ACT at the same time as first line treatments to reduce the selective pressure by each treatment regimen. No clear association between the presence of Pfcrt and Pfmdr1 alleles carried at baseline and treatment failure was observed.

Usefulness of the Plasmodium falciparum chloroquine resistance transporter T76 genotype failure index for the estimation of in vivo chloroquine resistance in Burkina Faso.

The prevalence of chloroquine (CQ) treatment failure and the genotype failure index was determined in four sentinel sites in Burkina Faso. In three sites, the genotype failure index varied between 1.7 and 3, a result confirming the relationship between the Plasmodium falciparum CQ resistance transporter (Pfcrt) T76 mutation and CQ resistance. In the remaining site, the genotype failure index was unusually low, 1.1, which was significantly different than that in the other sites (P < 0.00001). These findings are discussed. Often but not always, the prevalence of CQ resistance can be correctly estimated by the Pfcrt T76 genotype failure index.

Dynamic of plasmodium falciparum chloroquine resistance transporter gene Pfcrt K76T mutation five years after withdrawal of chloroquine in Burkina Faso.

We investigated the evolution of Pfcrt K76T mutation five years after the withdrawal of chloroquine in Burkina Faso. A total of 675 clinical isolates collected from October 2010 to September 2012 were successfully genotyped. Single nucleotide polymorphism in Pfcrt (codon 76) gene was analyzed. The prevalence of resistant Pfcrt 76T allele was 20.55%. There was a progressive decrease of the proportion of mutant type pfcrt T76 from 2010 to 2012 (X2=5.508 p=0.0189). Our results suggest a progressive return of the wild type Pfcrt K76 in Burkina Faso but the prevalence of the mutants Pfcrt T76 still remains high.

Relationship between the Pfcrt T76 and the Pfmdr-1 Y86 mutations in Plasmodium falciparum and in vitro/in vivo chloroquine resistance in Burkina Faso, West Africa.

The relationship between Pfcrt T76 and Pfmdr-1 Y86 mutations in Plasmodium falciparum was explored in samples from patients with uncomplicated malaria and tested in vitro and in vivo with chloroquine (CQ) in Burkina Faso. The two mutations were strongly related. The Pfcrt T76 mutation was found in 82% of the samples having the Pfmdr-1 Y86 mutation too (odds ratio (OR)=4.8 [95% CI: 1.7-13.3]; P=0.002). However, only half (16/34) of samples with Pfcrt T76 mutation had also the Pfmdr-1 Y86 mutation. The latter was apparently associated with in vitro resistance (OR=4.8 [95% CI: 1.4-16.5]; P=0.01) but such association disappeared (P=0.77) after adjusting for the presence of the Pfcrt T76 mutation. This suggests that the occurrence of the Pfmdr-1 Y86 mutation is dependent on that of Pfcrt T76 mutation and could explain previous reports linking the Pfmdr-1 Y86 mutation with CQ resistance (CQR). The isolates carrying both the Pfcrt K76 and Pfmdr-1 N86 alleles (wild/wild (WW)) and the single mutant Pfmdr-1 Y86 (WM) had the lowest IC50 geometric mean (GMIC50) values, while those carrying both Pfcrt T76/Pfmdr-1 Y86 alleles (mutant/mutant (MM)), and the single mutant Pfcrt T76 (MW) had the highest. Among pre-treatment samples there was a strong linkage disequilibrium with an excess of MM and WW and a deficit of single mutants (MW and WM), suggesting that parasite fitness is higher for the former and lower for the latter.

KDR mutation, a genetic marker to assess events of introgression between the molecular M and S forms of Anopheles gambiae (Diptera: Culicidae) in the tropical savannah area of West Africa.

A sodium channel 'kdr'-type mutation was identified in the M form of Anopheles gambiae from Burkina Faso in the tropical savannah area belt. The molecular M form of An. gambiae is found at high frequencies in the flooded rice cultivation area of Kou Valley, where the insecticide selection pressure is limited. The spread of the mutation in the M population is an ongoing process, as it increased from a frequency of 0.006 in 1999 to 0.02 in 2000. The S molecular form occurs in sympatry in our study village, with the M form at a relatively low frequency. The common 'kdr' mutation was previously detected in this area in the S form, and has probably invaded the M population through genetic introgression. This impacts on the question of actual levels of gene flow between the two molecular forms in tropical savannah areas. A hybrid M/S individual was identified during the course of this study, which was homozygous for the 'kdr' mutation. Pyrethroid resistant An. gambiae were caught in October and November, which is the time of year that the molecular S form migrates into this area as rain-fed breeding sites in the cotton fields dry out.

[Malaria transmission in 1999 in the rice field area of the Kou Valley (Bama), (Burkina Faso)]. / Etude de la transmission du paludisme en 1999 dans la zone rizicole de la vallée du Kou (Bama), (Burkina Faso).

A longitudinal study based on mosquitoes sampled by larvae prospecting and adult catches on humans was carried out during 1999 in the rice field area of the Kou Valley (South-West Burkina Faso) to evaluate the malaria transmission level. Two sites were studied: VK5 located in the rice field centre and VK7 in the periphery. Irrigation is sub-permanent and two crops are grown each year: from February to June during the dry season and from July to November during the rainy season. A man sleeping in VK5 without any protection is exposed to more than 60,000 mosquito bites/year. Two majors vectors are present: Anopheles gambiae sl. and An. funestus. The An. gambiae M form which breeds in rice fields constitutes the majority of the complex. At the periphery of the rice fields, we observed a mix of M and S forms during the rainy season, the latter form coming from classical breeding sites created by rainfall (residual puddles). An. arabiensis is rare in this environment while we can find it in sympathy with An. gambiae in the surrounding savannah. An. gambiae remains present throughout the year. Its dynamics depends closely on both season and rice cycle. There are two density peaks, in March (210 bites/man/night) and in July (306 b/m/n), corresponding to the moment when rice is planted. The latter peak is more important due to additional productivity of residual puddles created by rainfall. These large and very young populations can not transmit malaria. Growing rice reduces larvae productivity: transmission occurs when the adult population decreases and becomes older. Variations in parity rate and sporozoitic index are inversely related to mosquito density. Finally, the An. gambiae population is lowest during the dry season in January when irrigation stops. An. funestus does not develop in rice fields but rather in drains made of dirt, in addition to the classical natural breeding sites at the end of the rainy season. The density of An. funestus is 25 to 30 times smaller than that of A. gambiae, as observed during 8 months in VK5 and 10 months in VK7, with a peak of 16 b/m/n in January. Its mean parity rate and sporozoitic index is higher than those of An. gambiae. An. funestus plays an additional role in malaria transmission at the same period as An. gambiae but more shortly and less intensively. Finally, malaria transmission is due mainly to An. gambiae (90%) and, to a lesser extent, to An. funestus (10%). It occurs in VK5 during two periods of four month search : from May to August and from November to February. In VK7, transmission is also bimodal but it occurs more extensively throughout the year with only July and Septemberas exemptions of transmission. The annual inoculation rate amounts to 697 and 515 infected bites per man. This value is higher than those obtained in 1984/1985 : 50 and 60 infected bites per man per year. This increase is due to both the growth of aggressive vectorial density and the sporozoitic index. Growth of adult density can be explained by the environmental modification and/or better adaptation of vectorial species. The sporozoitic index of vectors has been obtained using Elisa, which is twice as sensitive as the microscopic observations used in 1984/1985. This can partly explain the increase in the sporozoitic index. Other hypotheses in relation to human parasitological inputs have to be evaluated more accurately. The level and rhythm of transmission in the rice field in 1999 are more important than those registered in the surrounding savannah the same year. However, this important transmission is not proportionally related to the high vectorial density found in rice fields. Probably, it does not imply more malaria diseases, but its intensity and rhythm could concentrate malaria cases in young people with an early acquisition of premunition. Pyrethroid impregnated bednets should be used to prevent malaria especially since high mosquito nuisance drives local populations to use it and since the An. gambiae M form is particularly susceptible to this class of insecticides.

[Parasitological resistance of Plasmodium falciparum to antimalarial drugs: what physicians should keep in mind]. / Attitude à propos de la résistance parasitologique de Plasmodium falciparum aux antipaludiques.

Plasmodium falciparum drug resistance has considerably modified the attitude of physicians in terms of malaria case management. However, a bad understanding of the resistance phenomenon can lead to non-appropriate therapeutic and/or public health practices. The objective of this paper was to contribute to clarify the concept of parasitological resistance by analysing the different types of resistance observed in vivo. We showed through some examples that the precision of in vivo parasitological results depends on the type of microscopical technique used. We also showed that the classification system into resistance levels RI, RII, and RIII does not correspond to an increase in the resistance of the parasite itself but rather to an increase in the proportion of the resistant strains compared to the sensitive ones circulating in a given population. Mutant strains are circulating in low proportions as long as there is no selective drug pressure. They can be first detected in vitro and, later on, when their proportion increase, they are detected in vivo, first in non-immune subjects and later in semi-immune subjects. Therefore, the role of the host immunity is important in malaria drug resistance. To conclude, increasing use of antimalarial drugs (especially in monotherapy) cannot thwart the resistance, but rather leads to the selection of mutants strains. As the proportion of the mutant strains increases compared to the sensitive (wild) ones, it will reach the microscopic detection level and then, the clinical level. It is important that physicians involved in malaria case management understand these notions in order to avoid non-appropriate therapeutic decisions.