Clinical, paraclinical and genetic aspects of autosomal recessive cerebellar ataxias (ARCA) in Mali.

Introduction: Autosomal recessive cerebellar ataxias (ARCA) are a group of rare and heterogynous neurodegenerative diseases mainly characterized by unbalance and walking difficulty and movement incoordination. Objectives: To clinically and paraclinically characterize ARCA in the department of Neurology at the Teaching Hospital of Point G and identify the underlying genetic defect. Patients and method: We have conducted a longitudinal and prospective study from January 2018 to December 2020. Patients with ARCA phenotype seen in the Department of Neurology at the Teaching Hospital of Point "G" were enrolled. Results: We have enrolled 7 families totaling 13 patients after giving an informed verbal and written consent. The sex ratio was 2.2 in favor of males, Kayes region and Fulani ethnic group were respectively the most represented region and ethnic group.Walking difficulty represented the major symptom followed by loss of vibration and joint sense, nystagmus, dysarthria and skeletal deformities. Alpha-foetoprotein level was high in one patient. Genetic testing confirmed Friedreich ataxia in one family and was not conclusive in 4 families. Conclusion: This study showed that ARCA are not uncommon in Mali and genetic testing is crucial to confirm the diagnosis.

Introduction: Les ataxies cérébelleuses autosomiques récessives (ACAR) constituent un groupe de maladies neurodégénératives rares et hétérogènes caractérisées essentiellement par un trouble de l'équilibre et de la marche, et un trouble de la coordination des mouvements. Objectifs: Caractériser les signes cliniques, paracliniques et génétiques des ataxies cérébelleuses autosomiques récessives au Service de Neurologie du CHU du Point "G". Patients et méthodes: Nous avons réalisé une étude de cas enrôlé dans le cadre d'une étude longitudinale et prospective allant de Janvier 2018 à Décembre 2020, portant sur des patients présentant des symptômes d'ACAR et ayant donné leur consentement éclairé. Résultats: Nous avons enrôlé sept familles totalisant 13 patients. Le sexe ratio était de 2,2 en faveur des hommes, la région de Kayes était la plus représentée et l'ethnie peulh était majoritaire. Les troubles de la marche ont représenté les signes majeurs suivis de troubles de la sensibilité profonde, de nystagmus, de dysarthrie, et des déformations ostéoarticulaires. L'alpha-foetoprotéine était élevée chez une patiente. Le test génétique a retrouvé l'ataxie de Friedreich dans une famille et n'a pas été concluant dans quatre autres. Conclusion: Cette étude montre que les ACAR ne sont pas rares au Mali et l'exploration génétique constitue un outil indispensable pour leur diagnostic de certitude.

Diagnostic et évaluation de la réponse thérapeutique de la leucémie myéloïde chronique au Mali par l'hybridation in situ fluorescente / Diagnosis and evaluation of the response to treatment of chronic myeloid leukaemia in Mali by fluorescent in situ hybridization

La leucémie myéloïde chronique (LMC) est une hémopathie maligne caractérisée par la présence du chromosome Philadelphie ou du gène de fusion BCR/ABL1. Au Mali, les approches génétiques de diagnostic et d'évaluation de la réponse thérapeutique de la LMC font défaut d'où l'intérêt de développer la méthode FISH (Hybridation in situ en Fluorescence) pour diagnostiquer et évaluer la réponse thérapeutique de la LMC. Méthodes. Nous avons analysé les cellules sanguines de 25 patients référés pour diagnostic ou évaluation thérapeutique de la LMC. Nous avons réalisé la FISH sur des cellules interphasiques et des métaphases, et la capture d'images cellulaires a été faite avec un microscope à épifluorescence. Résultats. Au total, 25 patients ont été inclus dont 16 pour diagnostic et 9 pour évaluation thérapeutique. Nous avons obtenu un taux de succès de 92% pour l'obtention des métaphases. En outre, nous avons observé des réarrangements ABL1/BCR à la FISH chez 22 des 25 patients. Parmi ces 22 patients, 16 ont présenté un patron de signaux typiques et 6 des patrons de signaux atypiques. Conclusion. Nous avons établi la technique FISH au Mali pour le diagnostic et l'évaluation thérapeutique de la LMC et identifié des formes atypiques de la translocation t(9 ;22).

Objective. Chronic myeloid leukemia (CML) is a hematologic malignancy characterized by the presence of the Philadelphia chromosome or its molecular equivalent, the BCR/ABL1 fusion gene. Diagnosis and monitoring of CML are done by detecting this chromosome, the BCR/ABL1 gene, or the BCR/ABL1 transcript. In Mali, genetic tools of diagnosis and follow-up are still lacking, so we did this study with the objectives of developing the FISH technique to diagnose, to follow up, and to characterize the cytogenetic profile of CML patients. Methods. We carried out FISH technique by using the dual color dual fusion probe for BCR/ABL1 on interphase nuclei and metaphases. Slides were scanned with an epifluorescence microscope. Results. A total of 25 patients (16 for diagnostic and 9 for follow-up) were included. We achieved a 92% success rate for obtaining metaphases. The BCR/ABL1 gene fusion signal was present in 22 patients. Among those 22 patients, 16 presented a typical signal pattern and 6 presented atypical signal patterns. Conclusion. We set up the FISH technique in Mali for the diagnosis and the follow-up of CML patients and identified atypical translocation of t(9;22).

Impact of seasonal malaria chemoprevention in children aged 3 to 59 months in the Kangaba and Kolokani health districts between 2013 and 2015.

INTRODUCTION: Malaria is a public health problem in Mali. Seasonal chemo prevention (SCP) is of particular importance, hence its introduction by the WHO since 2012 in children aged 3 to 59 months from the start of the transmission season. This study aims to demonstrate the impact of SCP on malaria in the health districts of Kangaba and Kolokani. MATERIALS AND METHODS: Our retrospective study was carried out from 2013 to 2015 in the health districts of Kangaba and Kolokani using the databases of the NGO AMCP / ALIMA. Data from 2014 and 2015 were compared to data from 2013. RESULTS: The number of malaria cases in children under 5year in the area covered by the SCP shows a considerable decrease in Kangaba of 52% in 2014 and 49% in 2015, compared to the reference period being the year 2013. In Kolokani the decrease is 57% in 2014 and 40% in 2015 compared to the year 2013. Compared to deaths, a decrease of 50.5% was recorded in 2014 and 60.4% in 2015 compared to the year 2013, i.e. 51 and 61 fewer deaths compared to 2013, respectively, in health facilities. CONCLUSION: The SCP had made it possible to reduce significant mortality and malaria morbidity in the two health districts of Kangaba and Kolokani.

INTRODUCTION: le paludisme est un problème majeur de santé publique au Mali. La chimio prévention saisonnier a une importance particulière d'où son instauration par l'OMS depuis 2012 chez les enfants de 3 à 59 mois à partir du début de la saison de transmission. Cette étude vise à démontrer l'impact de la CPS sur le paludisme dans les districts sanitaires de Kangaba et de Kolokani. MATÉRIELS ET MÉTHODES: Notre étude rétrospective a été réalisée de 2013 à 2015 dans les districts sanitaires de Kangaba et de Kolokani en utilisant les bases de données de l'ONG AMCP/ALIMA. Les données de 2014 et 2015 ont été comparés à ceux de 2013. RÉSULTATS: Le nombre de cas de paludisme chez les enfants de moins de 5 ans dans la zone couverte par la CPS montre une baisse considérable à Kangaba de 52% en 2014 et 49% en 2015, par rapport à la période de référence étant l'année 2013. A Kolokani la baisse est de 57% en 2014 et 40% en 2015 par rapport à 2013. Par rapport aux décès, une baisse de 50,5% a été enregistrée en 2014 et 60,4% en 2015 par rapport à 2013, soit respectivement 51 et 61 décès en moins comparé à 2013, dans les structures de santé. CONCLUSION: La CPS avait permis une réduction de la mortalité importante et de la morbidité palustre dans les deux districts sanitaires de Kangaba et de Kolokani.

Diversity of Sand Flies (Diptera: Psychodidae: Phlebotominae) in Two Different Eco-Climatic and Endemic Zones of Cutaneous Leishmaniasis in Mali, West Africa.

Being the only established vectors of the protozoan parasites of the genus Leishmania, sand flies have become very important in all countries where leishmaniasis exists. To better understand the sand fly fauna, a taxonomic inventory study was carried out between January and March 2012 in Soudan savannah (Boundioba, Sikasso) and Sahelian (Tieneguebougou, Koulikoro) areas of Mali. CDC light traps were used to collect the sand flies. Collected sand flies specimens were cleaned with lacto-phenol and examined under a light microscope for species identification. In total, 14 species belonging to the genera Phlebotomus and Sergentomyia were identified. The genus Sergentomyia constituted 98.05% of collected sand flies versus 1.95% for the genus Phlebotomus. The most abundant species were Sergentomyia dubia Parrot, Mornet, & Cadenat, Sergentomyia shwetzi, Sergentomyia clydei Sinton, and Sergentomyia antennata Newstead. In Boundioba, the genus Phlebotomus was represented by two species (Phlebotomus duboscqi Neveu-Lemaire and Phlebotomus rodhaini Parrot), whereas only one species, Ph. duboscqi, was captured in Tieneguebougou. For the first time, three new species, Sergentomyia madagascariensis, Sergentomyia congolensis, and Sergentomyia dureni, were identified in Mali. More investigations are needed for a better entomological assessment of the transmission of cutaneous leishmaniasis in the different eco-climatic zones of Mali.

[Susceptibility status of Anopheles gambiae sensu lato to insecticides commonly used for malaria control in Mali]. / Susceptibilité d'Anopheles gambiae sensu lato aux insecticides communément utilisés dans la lutte antivectorielle au Mali.

The objective of this work was to monitor the susceptibility of malaria vectors to insecticides in nine sentinel sites of the National Malaria Control Program in Mali. The study was performed during the rainy seasons of 2010 and 2011. WHO bioassays were conducted using F0 and/or F1 from wild collected females. The insecticides used were lambda-cyhalothrin 0.05%, DDT 4%, permethrin 0.75%, deltamethrin 0.05%, bendiocarb 0.1% and fenitrothion 1.0%. Results showed suspicion of resistance to pyrethroids and organochlorine in An. gambiae s.l. at almost all the sites except Yanfolila where the vector was susceptible to lambda-cyhalothrin (98.0%) [CI 95%, 98-99.8] and to DDT (100%). An. gambiae s.l. was susceptible to bendiocarb in five of the sites (Gao, Bougouni, Djenné, Yanfolila, Tombouctou) while there was a suspicion of resistance at the other sites (Kati, Niono, Bandiagara, Kita). Fenitrothion remains efficient except in the rice area of Niono, where there was a suspicion of resistance with a mortality rate of 92% [IC 95% 88.3-94.8]. Thus, it could be used as an alternative insecticide for IRS in Mali. These results show resistance to pyrethroids, the main insecticide family used in public health (and to some extent in agriculture). This could compromise the malaria vector control efforts in Mali where pyrethroids are used for both in bed nets and in IRS.

[Vectorial transmission of malaria in a village along the Niger River and its fishing hamlet (Kéniéroba and Fourda, Mali)]. / Transmission vectorielle du paludisme dans un village du bord du fleuve Niger et son hameau de pêche (Kéniéroba et Fourda, Mali).

A better understanding of malaria transmission dynamics is an essential element in the development of any targeted vector control strategy. The objective of this study was to better understand malaria transmission dynamics along the Niger River in Sudan savanna zone of Mali. Trough cross-sectional surveys, Anopheline larvae were collected by WHO standard dipping technique, and vector adults by Human Landing and pyrethrum spray catches methods. The vector population was composed of An. gambiae s.l. (> 99%) and An. funestus (< 1%). An. gambiae s.l. was composed of 96% and 98% of An. gambiae s.s. respectively in Kéniéroba and Fourda. An. gambiae s.s. was in majority composed of its molecular form M in both locations. The density of An. gambiae s.l was higher in the dry season in the immediate vicinity of the river (fishing hamlet Fourda) compared to farther inland Kéniéroba. The average infection rate of An. gambiae s.l. was 3.63% and 4.06% in Kéniéroba and Fourda respectively. The average entomological inoculation rate (EIR) during the study period was almost similar in Kéniéroba (0.70 infective bites/person/month) and Fourda (0.69 infective bites/person/month). The means EIRs over each of the rainy season 2006 and 2007 were always higher than the one of the dry season 2007 in both localities, with much smaller amplitude in Fourda than in Kéniéroba. However, the level of the transmission was 2.31 (0.37/0.16) times higher in Fourda than in Kéniéroba during the dry season.We conclude that in Sudan savanna zone of Mali, malaria transmission along the river is continuous throughout the year, but it is more intense in the immediate vicinity of the river during the dry season than during the rainy season in opposition to more distant localities to the river and vector control should not be focused only on the rainy in such setting.

[Knowledge and attitudes of medical personnel in blood transfusion in Bamako, Mali]. / Connaissances et attitudes du personnel médical en matière de transfusion sanguine au Mali.

PURPOSE OF THE STUDY: We undertook a study to determine the level of knowledge and practice of medical staff personnel on transfusion medicine in Mali at Bamako and Kati. PATIENTS AND METHODS: The study was conducted from January to April 2010 in the three main teaching hospitals of Bamako and Kati and in the six referral health centers of the district of Bamako. Medical staff knowledge and practice were assessed using a questionnaire. The study population consisted of specialized practitioners (15%), general practitioners (21.4%), nurses (41.6%), and midwives (22%). RESULTS: Overall, 70.9% of the staff did not receive any training in blood transfusion since their graduation. The general knowledge about blood transfusion was insufficient in 53.9% of staff and excellent in 46.1%. Only 42.9% of medical staff has a good basic knowledge of blood products, their indications, and related accidents. CONCLUSION: Our study showed weaknesses in the transfusion system in Bamako, with insufficient knowledge of the medical staff in blood transfusion and little experience.

Attraction of Stomoxys sp. to various fruits and flowers in Mali.

The attraction of three Stomoxys species to 26 fruits and 26 flowers of different plant species was investigated in two different sites in Mali during 2008. Stomoxys niger bilineatus Grunberg (Diptera: Muscidae) was attracted to a wider spectrum of species, significantly attracted by four fruits and eight flowers compared with control traps, whereas S. sitiens Rondani (Diptera: Muscidae) was attracted to six fruits and seven flowers of different plants, and S. calcitrans L. (Diptera: Muscidae) was only attracted to one fruit and three flowers. Cold anthrone assays showed a significantly higher prevalence of sugar feeding amongst all three species at the lagoon site than at the site near Mopti. The rhythm of activity study shows temporally separated blood- and sugar-feeding periods for S. niger bilineatus and S. sitiens, but not for S. calcitrans. A comparison between blood and sugar feeding throughout the day shows that sugar feeding activity is as frequent as blood feeding activity. Because not much is known about the preferred sugar sources for Stomoxys species in their natural habitats, the present study provides valuable information regarding the attraction capability of several plants with possible future implication for Stomoxys control strategies.

SNP genotyping defines complex gene-flow boundaries among African malaria vector mosquitoes.

Mosquitoes in the Anopheles gambiae complex show rapid ecological and behavioral diversification, traits that promote malaria transmission and complicate vector control efforts. A high-density, genome-wide mosquito SNP-genotyping array allowed mapping of genomic differentiation between populations and species that exhibit varying levels of reproductive isolation. Regions near centromeres or within polymorphic inversions exhibited the greatest genetic divergence, but divergence was also observed elsewhere in the genomes. Signals of natural selection within populations were overrepresented among genomic regions that are differentiated between populations, implying that differentiation is often driven by population-specific selective events. Complex genomic differentiation among speciating vector mosquito populations implies that tools for genome-wide monitoring of population structure will prove useful for the advancement of malaria eradication.

Establishing an insect disease vector functional genomics training center in Africa.

The genome sequences for many insects vector of human diseases are now available and promise the development of a set of new, powerful tools that can be used to develop innovative approaches to control these diseases. The African continent, which is the most severely affected by vector borne diseases, lacks adequate infrastructures and personal resources required for rational use of genomic information. To fill this gap, the African Center for Training in Functional Genomics of Insect vectors of Human Disease (AFRO VECTGEN) was initiated by WHO/TDR and the Department of Medical Entomology and Vector Ecology (DMEVE) of the Malaria Research and Training Center (MRTC) in Mali. The aim of the AFRO VECTGEN program is to train young scientists in functional genomics who will ultimately use genome sequence data for research on insect vector of human disease. The program could trigger collaborative research and will benefit from an existing vector biology network in Mali, which was built around research grants funded by the National Institutes of Health, USA and WHO/TDR.

Evidence for subdivision within the M molecular form of Anopheles gambiae.

The principal vector of malaria in sub-Saharan Africa, Anopheles gambiae is subdivided into two molecular forms M and S. Additionally, several chromosomal forms, characterized by the presence of various inversion polymorphisms, have been described. The molecular forms M and S each contain several chromosomal forms, including the Savanna, Mopti and Forest forms. The M and S molecular forms are now considered to be the reproductive units within A. gambiae and it has recently been argued that a low recombination rate in the centromeric region of the X chromosome has facilitated isolation between these forms. The status of the chromosomal forms remains unclear however. Therefore, we studied genetic differentiation between Savanna S, Forest S, Forest M and Mopti M populations using microsatellites. Genetic differentiation between Savanna S and Forest S populations is very low (F(ST) = 0.0053 +/- 0.0049), even across large distances. In comparison, the Mopti M and Forest M populations show a relatively high degree of genetic differentiation (F(ST) = 0.0406 +/- 0.0054) indicating that the M molecular form may not be a single entity, but could be subdivided into at least two distinct chromosomal forms. Previously it was proposed that inversions have played a role in the origin of species within the A. gambiae complex. We argue that a possible subdivision within the M molecular form could be understood through this process, with the acquisition of inversions leading to the expansion of the M molecular form into new habitat, dividing it into two distinct chromosomal forms.

The spatial distribution of Anopheles gambiae sensu stricto and An. arabiensis (Diptera: Culicidae) in Mali.

Variations in the biology and ecology and the high level of genetic polymorphism of malaria vectors in Africa highlight the value of mapping their spatial distribution to enhance successful implementation of integrated vector management. The objective of this study was to collate data on the relative frequencies of Anopheles gambiae s.s. and An. arabiensis mosquitoes in Mali, to assess their association with climate and environmental covariates, and to produce maps of their spatial distribution. Bayesian geostatistical logistic regression models were fitted to identify environmental determinants of the relative frequencies of An. gambiae s.s. and An. arabiensis species and to produce smooth maps of their geographical distribution. The frequency of An. arabiensis was positively associated with the normalized difference vegetation index, the soil water storage index, the maximum temperature and the distance to water bodies. It was negatively associated with the minimum temperature and rainfall. The predicted map suggests that, in West Africa, An. arabiensis is concentrated in the drier savannah areas, while An. gambiae s.s. prefers the southern savannah and land along the rivers, particularly the inner delta of Niger. Because the insecticide knockdown resistance (kdr) gene is reported only in An. gambiae s.s. in Mali, the maps provide valuable information for vector control. They may also be useful for planning future implementation of malaria control by genetically manipulated mosquitoes.

Reproductive output of female Anopheles gambiae (Diptera: Culicidae): comparison of molecular forms.

Knowledge of ecological differences between the molecular forms of Anopheles gambiae Giles (Diptera: Culicidae) might lead to understanding of their unique contribution to disease transmission, to better vector control, and to identification of the forces that have separated them. We compared female fecundity measured as egg batch size in relation to body size between the molecular forms in Mali and contrasted them with their sibling species, Anopheles arabiensis Patton. To determine whether eggs of different egg batches are of similar "quality," we compared the total protein content of first-stage larvae (L1s), collected < 2 h after hatching in deionized water. Egg batch size significantly varied between An. gambiae and An. arabiensis and between the molecular forms of An. gambiae (mean batch size was 186.3, 182.5, and 162.0 eggs in An. arabiensis and the M and the S molecular form of An. gambiae, respectively). After accommodating female body size, however, the difference in batch size was not significant. In the S molecular form, egg protein content was not correlated with egg batch size (r = -0.08, P > 0.7) nor with female body size (r = -0.18, P > 0.4), suggesting that females with more resources invest in more eggs rather than in higher quality eggs. The mean total protein in eggs of the M form (0.407 microg per L1) was 6% higher than that of the S form (0.384 microg per L1), indicating that the M form invests a greater portion of her resources into current (rather than future) reproduction. A greater investment per offspring coupled with larger egg batch size may reflect an adaptation of the M form to low productivity larval sites as independent evidence suggests.

Patterns of irrigated rice growth and malaria vector breeding in Mali using multi-temporal ERS-2 synthetic aperture radar.

We explored the use of the European Remote Sensing Satellite 2 Synthetic Aperture Radar (ERS-2 SAR) to trace the development of rice plants in an irrigated area near Niono, Mali and relate that to the density of anopheline mosquitoes, especially An. gambiae. This is important because such mosquitoes are the major vectors of malaria in sub-Saharan Africa, and their development is often coupled to the cycle of rice development. We collected larval samples, mapped rice fields using GPS and recorded rice growth stages simultaneously with eight ERS-2 SAR acquisitions. We were able to discriminate among rice growth stages using ERS-2 SAR backscatter data, especially among the early stages of rice growth, which produce the largest numbers of larvae. We could also distinguish between basins that produced high and low numbers of anophelines within the stage of peak production. After the peak, larval numbers dropped as rice plants grew taller and thicker, reducing the amount of light reaching the water surface. ERS-2 SAR backscatter increased concomitantly. Our data support the belief that ERS-2 SAR data may be helpful for mapping the spatial patterns of rice growth, distinguishing different agricultural practices, and monitoring the abundance of vectors in nearby villages.

[Presence and risk of transmission of Wuchereria bancrofti is a reality in rural Mali: the case of the town of Bariambani in the Cirle of Kati]. / La presence et le risque de transmission de Buchereria bancrofti est une realite en Milieu rural au Mali: le cas du village de Banambani dans le Cercle de Kati.

Previous studies on lymphatic filariasis in Mali showed high infection rate in rural area. This study was aimed to find Wuchereria bancrofti microfilaria in human peripheral blood and larvae in vectors. For that purpose we carried out an entomological, clinical and parasitological study in Banambani a village located at 25 km from Bamako the capital city. The parasitological and clinical study was a single cross sectional study including night blood thick smear and physical examination. The entomological study was longitudinal with three annual surveys at the beginning, the middle and the end of the rainy season with parasite detection on vector by PCR. The infection rates by night thick smear was 1.5% of the study sample. The transmission was assured by Anopheles gambiae s.l and Anopheles funestus. Wuchereria bancrofti larvae have been detected on 0.5% of the vectors. The higher entomological inoculation rate (EIR) for An. gambiae s.l has been observed in August (4.03 infective bites per man per night) and in October for An. funestus (1.9 infective bites per man per night). Lymphatic filariasis is present in Malian rural area and transmission still occurring.

Mapping rice field anopheline breeding habitats in Mali, West Africa, using Landsat ETM+ sensor data.

The aim of this study was to determine whether remotely sensed data could be used to identify rice-related malaria vector breeding habitats in an irrigated rice growing area near Niono, Mali. Early stages of rice growth show peak larval production, but Landsat sensor data are often obstructed by clouds during the early part of the cropping cycle (rainy season). In this study, we examined whether a classification based on two Landsat Enhanced Thematic Mapper (ETM)+ scenes acquired in the middle of the season and at harvesting times could be used to map different land uses and rice planted at different times (cohorts), and to infer which rice growth stages were present earlier in the season. We performed a maximum likelihood supervised classification and evaluated the robustness of the classifications with the transformed divergence separability index, the kappa coefficient and confusion matrices. Rice was distinguished from other land uses with 98% accuracy and rice cohorts were discriminated with 84% accuracy (three classes) or 94% (two classes). Our study showed that optical remote sensing can reliably identify potential malaria mosquito breeding habitats from space. In the future, these 'crop landscape maps' could be used to investigate the relationship between cultivation practices and malaria transmission.

Gene flow among populations of the malaria vector, Anopheles gambiae, in Mali, West Africa.

The population structure of the Anopheles gambiae complex is unusual, with several sibling species often occupying a single area and, in one of these species, An. gambiae sensu stricto, as many as three "chromosomal forms" occurring together. The chromosomal forms are thought to be intermediate between populations and species, distinguishable by patterns of chromosome gene arrangements. The extent of reproductive isolation among these forms has been debated. To better characterize this structure we measured effective population size, N(e), and migration rates, m, or their product by both direct and indirect means. Gene flow among villages within each chromosomal form was found to be large (N(e)m > 40), was intermediate between chromosomal forms (N(e)m approximately 3-30), and was low between species (N(e)m approximately 0.17-1.3). A recently developed means for distinguishing among certain of the forms using PCR indicated rates of gene flow consistent with those observed using the other genetic markers.

[Malaria transmission in the rural zone of Niakhar, Senegal]. / La transmission du paludisme dans la zone de Niakhar, Sénégal.

The anopheline bioecology and the malaria transmission were studied from January to December 1995 in three villages of the sahelian rural area of Niakhar, Senegal. This area of 29000 inhabitants, has been for several decades, a regional observatory for population and health. The three methods used for collecting mosquitoes were the collection at larval stages, the all night human biting collection, and the pyrethrum spray catch in houses during afternoons. The anophelines collected were, by numerical importance: Anopheles arabiensis, An. rufipes, An. gambiae, An. pharoensis, An. funestus and An. coustani. In the An. gambiae complex, An. arabiensis represented 97% of man biting females and 98% of half gravid resting females (difference not significant); the other reminding species of this complex was always An. gambiae. These two species belonging to the An. gambiae complex were responsible for the totality of the transmission. The anthropophilic index, obtained from half gravid indoor resting An. gambiae s.l., was 83%. The annual biting rate of An. gambiae s.l. varied from 512 to 1558 bites per man per night, depending on the villages. Vectors were observed all year long but their densities were low during the dry season. Vector population presented a notable increase due to the rains, with a maximum of about 10 bites per man per night in September or at the beginning of October; during September the biting rate represented 48% of the annual biting rate. The sporozoitic index of An. gambiae s.l., obtained by ELISA revealing the circumsporozoite protein, was 1.6% for human biting females and 1.8% for half-gravid resting females (difference not significant). Plasmodium falciparum was the only plasmodial species observed among infected anophelines. The annual transmission in the vo villages representative of the Niakhar area were 9 and 12 bites of infected anophelines per man, occurring mainly from August to October. In the third village, not representative of the area regarding permanent breeding places, the transmission was 26 bites of infected anopheline per man per year. These results were discussed in the Senegambian and sahelian contexts.

Mark-release-recapture experiments with Anopheles gambiae s.l. in Banambani Village, Mali, to determine population size and structure.

Mark-release-recapture experiments with Anopheles gambiae s.l. were performed during the wet seasons of 1993 and 1994 in Banambani, Mali. All recaptured mosquitoes were identified to species by PCR analysis and, when possible, by chromosomal analysis to chromosomal form. Two species of the An. gambiae complex were present: An. gambiae s.s. and An. arabiensis; their ratio differed greatly from one year to the next. Three chromosomal forms of An. gambiae s.s. were found--Bamako, Savanna and Mopti. The drier 1993 was characterized by a high frequency of An. arabiensis and of the Mopti chromosomal forms of An. gambiae s.s. These trends were consistent with large-scale geographical patterns of abundance along a precipitation gradient. We observed no difference in dispersal between the two species, nor among the chromosomal forms of An. gambiae s.s. Therefore, in this situation at least, it is reasonable to group such data on the An. gambiae complex as a whole for analysis. Population size of An. gambiae s.l. females in the village was estimated to be 9000-11,000 in 1993 and 28,000 in 1994. The corresponding numbers were somewhat higher when independently-derived values of daily survival were used. These were consistent with estimates of effective population size obtained from patterns of gene frequency change.