Detection of kdr and ace-1 mutations in wild populations of Anopheles arabiensis and An. melas in a residual malaria transmission area of Senegal.

In the central western Senegal, malaria transmission has been reduced low due to the combination of several effective control interventions. However, despite this encouraging achievement, residual malaria transmission still occurring in few areas, mainly ensured by An. arabiensis and An. melas. The resurgence or the persistence of the disease may have originated from the increase and the spread of insecticide resistance genes among natural malaria vectors populations. Therefore, assessing the status and mechanisms of insecticides resistance among targeted malaria vectors is of highest importance to better characterize factors underlying the residual transmission where it occurs. Malaria vectors were collected from three selected villages using nocturnal human landing catches (HLC) and pyrethrum spray collections (PSC) methods. An. gambiae s.l. specimens were identified at the species level then genotyped for the presence of kdr-west (L1014F), kdr-east (L1014S) and ace-1R mutations by qPCR. An. arabiensis (69.36%) and An. melas (27.99%) were the most common species of the Gambiae complex in the study area. Among An. arabiensis population, the allelic frequency of the kdr-east (22.66%) was relatively higher than for kdr-west mutation (9.96%). While for An. melas populations, the overall frequencies of both mutations were very low, being respectively 1.12% and 0.40% for the L1014S and L1014F mutations. With a global frequency of 2%, only the heterozygous form of the G119S mutation was found only in An. arabiensis and in all the study sites. The widespread occurrence of the kdr mutation in both An. arabiensis and An. melas natural populations, respectively the main and focal vectors in the central-western Senegal, may have contributed to maintaining malaria transmission in the area. Thus, compromising the effectiveness of pyrethroids-based vector control measures and the National Elimination Goal. Therefore, monitoring and managing properly insecticide resistance became a key programmatic intervention to achieve the elimination goal where feasible, as aimed by Senegal. Noteworthy, this is the first report of the ace-1 mutation in natural populations of An. arabiensis from Senegal, which need to be closely monitored to preserve one of the essential insecticide classes used in IRS to control the pyrethroids-resistant populations.

Prominent intraspecific genetic divergence within Anopheles gambiae sibling species triggered by habitat discontinuities across a riverine landscape.

The Anopheles gambiae complex of mosquitoes includes malaria vectors at different stages of speciation, whose study enables a better understanding of how adaptation to divergent environmental conditions leads to evolution of reproductive isolation. We investigated the population genetic structure of closely related sympatric taxa that have recently been proposed as separate species (An. coluzzii and An. gambiae), sampled from diverse habitats along the Gambia river in West Africa. We characterized putatively neutral microsatellite loci as well as chromosomal inversion polymorphisms known to be associated with ecological adaptation. The results revealed strong ecologically associated population subdivisions within both species. Microsatellite loci on chromosome-3L revealed clear differentiation between coastal and inland populations, which in An. coluzzii is reinforced by a unusual inversion polymorphism pattern, supporting the hypothesis of genetic divergence driven by adaptation to the coastal habitat. A strong reduction of gene flow was observed between An. gambiae populations west and east of an extensively rice-cultivated region apparently colonized exclusively by An. coluzzii. Notably, this 'intraspecific' differentiation is higher than that observed between the two species and involves also the centromeric region of chromosome-X which has previously been considered a marker of speciation within this complex, possibly suggesting that the two populations may be at an advanced stage of differentiation triggered by human-made habitat fragmentation. These results confirm ongoing ecological speciation within these most important Afro-tropical malaria vectors and raise new questions on the possible effect of this process in malaria transmission.

[Comparative prognosis of pulmonary embolism in patients infected with COVID-19 and patients not infected with COVID-19 in Ouagadougou]. / Pronostic comparé de l'embolie pulmonaire chez les patients infectés au COVID-19 et les patients non infectés au COVID-19 à Ouagadougou.

OBJECTIVE: the study's objective was to determine impact of COVID-19 on the prognosis of pulmonary embolism. PATIENTS AND METHODS: An analytical multicenter cross-sectional study with retrospective data collection was carried out in three university hospitals and a private clinic in Ouagadougou from March, 2020 to July 2021. It included consecutive patients hospitalized for PE confirmed on chest CT angiography or by the association an acute cor pulmonale on echocardiography-Doppler with deep vein thrombosis on venous ultrasound-Doppler of the lower limbs and having carried out a COVID-19 test (RT-PCR or rapid diagnostic test). Control cases consisted of all COVID-19 negative PE cases. Data comparison was carried out using the Epi info 7 software. A univariate then multivariate analysis allowed the comparison of the prognosis of the two subpopulations. The significance level retained was p < 0.05. RESULTS: 96 patients with COVID-19+ and 70 COVID-19- PE were included. The prevalence of PE in patients hospitalized for COVID-19 was 7.05%. The average patient age was 61.5±17 years for COVID-19+ patients and 49.6±15.9 years for COVID-19- patients. Pulmonary condensation syndrome (p=0.007), desaturation (p=0.0003) and respiratory distress syndrome (p=0.006) were more common in COVID-19+ patients. The hospital death rate was 27.1% in COVID-19+ patients and 10% in COVID-19- patients (p=0.0024). Age > 65 years and COVID-19 pneumonia were the independent factors of death. CONCLUSION: COVID-19 is associated with clinical severity and excess mortality in patients with pulmonary embolism.

The mosquito Aedes (Aedimorphus) vexans arabiensis as a probable vector bridging the West Nile virus between birds and horses in Barkedji (Ferlo, Senegal).

Active catches of adult females of Aedes vexans arabiensis Patton, (Diptera: Culicidae) Patton by nets or aspirator, were conducted in 2003 and 2004 in the vegetation at the edge of temporary ponds in Barkedji, Senegalese Ferlo area. Two hundred and forty-one engorged females were captured, dissected and the gut content adsorbed on a Whatman filter paper and analysed using the enzyme-linked immunosorbent assay (ELISA) technique to determinate the bloodmeal origin. Results indicated that Ae v. arabiensis fed primarily on mammals, including horses (35.7% of the bloodmeals), but also on birds (10%). Moreover, associations between horses and birds accounted for 42% of the mixed bloodmeals. These results show an opportunistic feeding behaviour and suggest that Ae v. arabiensis is a probable vector bridging the West Nile virus between horses and birds hosts in the Ferlo area.

[Evaluation of the quality-of-life of patients with pacemakers : experience of Burkina Faso about 120 patients paired with the collaboration of doctors from AUVERGNE (France)]. / Évaluation de la qualité de vie des patients porteurs d'un stimulateur cardiaque (pacemaker) : expérience du Burkina Faso à propos de 120 patients appareillés avec la collaboration des médecins d'Auvergne (France).

INTRODUCTION: In Burkina Faso, cardiac stimulation was introduced in October 2000 has grown over time.In orderto evaluate the effectiveness of stimulation on life, we proposed to evaluate the quality of life of patients with a pacemaker. GENERAL OBJECTIVE: to study the effect of the pacemaker on the quality of life of patients PATIENTS AND METHODS: This was a cross-sectional study aimed at describingthe wearers of a pacemaker for at least six months at the Yalgado OUEDRAOGO University Hospital and the Schiphramedical center.The AQUAREL questionnaire has been adapted to our context to establish a quality-of-life score. RESULTS: The mean age of the study population was 68 years with a female predominance (53.3%). Complete atrioventricular block was the main indication of stimulation in 55%. The average duration of implantation was 41.6 months with extremes of 8 and 128 months. The primo implantation was found in 79.1 % of patients against 18.3 % for a first change of case and2.5 % for a second change of housing. Double chamber stimulation was performed in 65% of cases. DDD mode was the most used followed by VVIR. The average quality of life score was 90.12. Negative predictors of quality of life were age and female.A correlation between quality-of-life score and age, hypertension and dyslipidemia was found (p< 0.05). On the other hand, no correlation between the number of implantation, the duration of implantation and the mode of stimulation was found (p> 0.05). CONCLUSION: patients with a pacemaker have a good quality of life. However, quality-of-life is not correlated with the number of pacemakers, nor the duration and mode of stimulation.

[Assessment of medical management of heart failure at National Hospital Blaise COMPAORE]. / Évaluation de la prise en charge médicale de l'insuffisance cardiaque à l'hôpital national Blaise COMPAORE.

AIM: The aim of this study was to assess the quality of medical management of heart failure at the National Hospital Blaise Compaoré according to the international guidelines. PATIENTS AND METHODS: A retrospective study was performed including consecutive patients admitted for heart failure documented sonographically from October 2012 to March 2015 in the Medicine and Medical Specialties Department of National Hospital Blaise Compaore with a minimum follow-up of six weeks. Data analysis was made by the SPSS 20.0 software. RESULTS: Eighty-four patients, mean age of 57.61±18.24 years, were included. It was an acute heart failure in 84.5% of patients with systolic left ventricular function impaired (77.4%). The rate of prescription of different drugs in heart failure any type was 88.1% for loop diuretics; 77.1% for angiotensin-converting enzyme inhibitors/angiotensin receptor blockers and 65.5% for betablockers. In patients with systolic dysfunction, 84.62% of patients were received the combination of angiotensin-converting enzyme inhibitors/angiotensin receptor blockers and 75.38% for betablockers. Exercise rehabilitation was undergoing in 10.7% of patients. The death rate was 16.7% and hospital readmission rate of 16.7%. CONCLUSION: The prescription rate of major heart failure drugs is satisfactory. Cardiac rehabilitation should be developed.

[Plasmodium falciparum chloroquine and pyrimethamine resistance monitoring network with molecular tools in the Niger River valley, Republic of Niger]. / Réseau de surveillance moléculaire de la chimioré- sistance de Plasmodium falciparum a la chloroquine et a la pyriméthamine dans la vallée du fleuve Niger, au Niger.

Plasmodium falciparum resistance to chloroquine first arose in Africa 25 years ago. Nowadays most of African malaria control programmes have switched their first-line treatment of uncomplicated malaria cases towards artemisinin derivatives combination. After WHO guidelines, a survey network for malaria treatment resistance has been set up in the Niger valley around Niamey since December 2004. The association of the Niger national malaria control programme with the CERMES research center allowed collecting of samples from both health centers and hospitals of this region. Blood finger-pricks on filter papers were tested for detection of plasmodial antigen in health center without biological diagnosis capacity. Specimens found positive either in hospital laboratory or by using antigen method were tested by PCR/RFLP to detect K76T mutations on the pfcrt gene and S108N mutation on the pfdhfr gene. This simple procedure allows the screening of a large number of specimens. Moreover, a spatial distribution of mutations and evidence of resistance clusters were searched integrating the data in a geographic information system. The 76T mutation of pfcrt and 108N of pfdhfr were respectively found in 50.8% and 57% of the specimens tested. No statistically significant difference was found according to the level of sanitary formations or the age of the patients. No resistance cluster was identified and the prevalence of mutation seems homogeneous in the zone. By completing the clinical efficacy studies we think that our simple method for collecting and testing blood samples associated with clinical efficacy studies may be useful for building a network of malaria drug resistance in Africa.

[Evaluation of Physical Integrity and Biological Efficacy of Two Types of LLINs Aged 5 to 36 Months Sampled in 11 Districts of Senegal]. / Évaluation de l'état physique et de l'efficacité biologique de deux types de moustiquaires imprégnées à longue durée d'action utilisés depuis 5 à 36 mois et collectés dans 11 districts du Sénégal.

The long-lasting insecticidal nets (LLINs) have been promulgated to compensate the low re-impregnation rate of conventional mosquito nets. Today, the cornerstone of the fight against malaria vectors is based on a large distribution of these LLINs for universal coverage. Despite this promotion, the question of their effective life in operational conditions remains unresolved. Between September and October 2013, a survey was conducted in 11 districts of Senegal where LLINs were sampled and routed to the laboratory for assessing their physical integrity and biological effectiveness. A total of 207 LLINs that were sampled in the 11 districts have been monitored during this study. Our results showed that Olyset® Net and PermaNet® 2.0 are the most represented brands in the districts. These two major brands have a good biological efficiency providing a high rate of knockdown despite their failing physical integrity.

Les moustiquaires imprégnées à longue durée d'action (MILDA) ont été promues pour pallier le faible taux de réimprégnation des moustiquaires conventionnelles. Aujourd'hui, la pierre angulaire de la lutte antivectorielle repose sur une forte distribution de ces MILDA pour une couverture universelle. En dépit de cette promotion, la question de leur durée de vie effective en conditions opérationnelles reste toujours posée. Entre septembre et octobre 2013, une enquête a été menée dans 11 districts du Sénégal. Des MILDA y ont été échantillonnées et acheminées au laboratoire pour évaluer leur intégrité physique et leur efficacité biologique. Au total, 207 MILDA ont été collectées dans les 11 districts suivis au cours de cette étude. Nos résultats ont montré que les deux marques majoritairement distribuées présentaient une bonne efficacité biologique, car induisant un taux élevé de knock-down malgré leur état détérioré.

[Effectiveness of three biological larvicides and of an insect growth regulator against Anopheles arabiensis in Senegal]. / Efficacité de trois larvicides d'origine biologique et d'un régulateur de croissance contre Anopheles arabiensis au Sénégal.

Urban malaria is a major public health problem in Africa. In Senegal, the environmental changes seem to favor the persistence of malaria transmission in Dakar suburbs by creating, throughout the year, potential breeding sites of malaria vectors. In such a situation and in a context of a growing threat of insecticide resistance in anopheline vectors, the larval control making use of products from biological origin or growth regulators could represent an additional tool to the current strategies developed against anophelines. In this study conducted in 2012, the efficiency and residual effect of three biological larvicides (VectoBac® WG, Vecto-Max® CG, and VectoBac® GR) and an insect growth regulator (MetaLarv™) were evaluated on Anopheles gambiae s.l. larvae in seminatural conditions (experimental station) and natural breeding sites in the suburbs of Dakar. The formulations were tested according to the manufacturer recommendations, namely 0.03 g/m2 for VectoBac® WG, 0.5 g/m2 for VectoBac® GR, 0.75 g/m2 for VectoMax® CG, and 0.5 g/m2 for MetaLarv™. In experimental station, the treatment with larvicides was effective over a period of 14 days with a mortality ranging between 92% and 100%. The insect growth regulator remained effective up to 55 days with a single emergence recorded in the 27th day after treatment. In natural conditions, a total effectiveness (100% mortality) of larvicides was obtained 48 hours after treatment, then a gradual recolonization of breeding sites was noted. However, the insect growth regulator has reduced adult emergence higher than 80% until the end of follow-up (J28). This study showed a good efficiency of the larvicides and of the growth regulator tested. These works provide current data on potential candidates for the implementation of larval control interventions in addition to that of chemical adulticide for control of urban malaria.

[Five years assessment of cardiac stimulation in two public hospitals in Burkina Faso: An experiment of collaboration with two hospitals in Auvergne]. / Bilan de cinq ans de stimulation cardiaque dans deux structures hospitalières publiques du Burkina Faso : expérience d'une collaboration avec deux centres hospitaliers d'Auvergne.

OBJECTIVES: Cardiac stimulation becomes a reality in Burkina Faso. The aim of our study was to evaluate this activity over five years and to appreciate the impact of collaboration with French hospitals of Auvergne area in its development. MATERIALS AND METHODS: Prospective study including consecutively patients who underwent pacemaker implantation since June 2011. Data collected included indications, time to care, type of stimulation, complications, cost of treatment, and education and quality of life of the patient. RESULTS: Sixty-nine patients received definitive pacemaker from June 2011 to June 2016, of whom 45.5% were women. The mean age was 69 years (extremes 35 to 89s). Almost all patients (94%) were symptomatic (54% syncope and 30% dizziness and lipothymias). The main indication for definitive cardiac pacing was complete atrioventricular block of degenerative origin (83%). The mean time between indication and surgery was 8.2 days, and only 4% of patients received temporary stimulation. The lack of financial support was the main reason for the delay in taking charge. During the study period, the two health centers received support in the form of stimulation equipment, a technical platform, and regular training and practical training. This collaboration made it possible to overcome the lack of material, human and financial resources. We recorded as complications a case of case exteriorization, two cases of benign local hematoma and two cases of probe displacement. The quality of life of the patients improved markedly, none of patients undergoing surgery remained symptomatic. CONCLUSION: The organization of cardiac stimulation in Burkina Faso is a reality. Efforts must be made to sustain the activity and strengthen collaboration with hospitals in the north.

[Identification of anopheles breeding sites in the residual foci of low malaria transmission «hotspots¼ in Central and Western Senegal]. / Identification des gîtes larvaires d'anophèles dans les foyers résiduels de faible transmission du paludisme « hotspots ¼ au centre-ouest du Sénégal.

Malaria incidence has markedly declined in the Mbour, Fatick, Niakhar and Bambey districts (central and western Senegal) thanks to a scaling up of effective control measures namely LLINs (Long Lasting Insecticide Treated Net), ACTs (Artesunate Combination Therapy) and promoting care seeking. However malaria cases are now maintained by foci of transmission called hotspots. We evaluate the role of anopheles breeding sites in the identification of malaria hotspots in the health districts of Mbour, Fatick, Niakhar and Bambey. Surveys of breeding sites were made in 6 hotspot villages and 4 non-hotspot villages. A sample was taken in each water point with mosquito larvae by dipping method and the collected specimens were identified to the genus level. Additional parameters as name of the village and breeding sites, type of collection, original water turbidity, presence of vegetation, proximity to dwellings, geographic coordinates, sizes were also collected. Sixty-two water collections were surveyed and monitored between 2013 and 2014. Temporary natural breeding sites were predominant regardless of the epidemiological status of the village. Among the 31 breeding sites located within 500 meters of dwellings in hotspots villages, 70% carried Anopheles larvae during the rainy season while 43% of the 21 breeding sites located at similar distances in non-hotspot villages carried Anopheles larvae during the same period (P = 0.042). At the end of the rainy season, the trend is the same with 27% of positive breeding sites in hotspots and 14% in non-hotspots villages. The breeding sites encountered in hotspots villages are mostly small to medium size and are more productive by Anopheles larvae than those found in non-hotspot area. This study showed that the high frequency of smallest and productive breeding sites around and inside the villages can create conditions of residual transmission.

[Acceptability of indoor residual spraying in the Central-Western of Senegal]. / Étude de l'acceptabilité de l'aspersion intradomiciliaire d'insecticide à effet rémanent dans le centre-ouest du Sénégal.

The recent decline of malaria transmission in central-western of Senegal after a scaling up of control measures gives an open window for interventions toward malaria elimination. As a consequence, malaria transmission is now occurring as hotspots. The aim of the project is to evaluate whether target control measures combining indoor residual spraying (IRS) with chemoprophylaxis can virtually eliminate malaria in hotspots. Targeted villages located in four (4) health districts (Mbour, Fatick, Niakhar and Bambey) were sprayed in august 2013 with Actellic® 300 CS (Pirimiphosmethyl). Our objective in this study is to evaluate the acceptability of IRS in the population. IRS is a very complex intervention that requires strong adhesion of populations. After its implementation, 370 households have been interviewed. The results of this survey showed good acceptability of IRS using Actellic® 300 CS, with 97.8% of beneficiaries who declared that IRS is good and even excellent for the community. Despite inconveniences that may arise during intervention, including the preparation of structures to be treated, 98% of respondents were not disturbed in their daily activities. 98.6% of responders declared that sprayers were working with professionalism and almost all households (99.7%) are willing to accept IRS next year. The survey revealed a good acceptability of indoor residual spraying in hot spots located in central-western of Senegal; spraying with Actellic® 300 CS did not cause a problem to the targeted populations. Finally, there is great satisfaction in the population due a huge reduction of mosquito nuisances.

Different genetic characteristics of Plasmodium falciparum isolates collected during successive clinical malaria episodes in Senegalese children.

A narrow epidemiologic survey was conducted during a four-month period of intense malaria transmission in Dielmo, a holoendemic Senegalese village. Longitudinal clinical and parasitologic follow-up indicate that clinical malaria episodes always occurred after an abrupt increase in parasite densities. Polymerase chain reaction analysis of Plasmodium falciparum parasites was carried out in blood samples collected longitudinally from 10 children who had experienced several clinical episodes during this period. Our data show that the genetic diversity of the parasites circulating in this village is very large. The successive clinical episodes experienced by each child were caused by genetically distinct parasite populations that were recently inoculated and multiplied in an apparently unrestricted manner. Importantly, the genetic characteristics of the parasite populations detected during phases of asymptomatic carriage differed from those causing a clinical episode, suggesting that the various factors that control of parasite growth in these children are strain-specific.

The Dielmo project: a longitudinal study of natural malaria infection and the mechanisms of protective immunity in a community living in a holoendemic area of Senegal.

The Dielmo project, initiated in 1990, consisted of long-term investigations on host-parasite relationships and the mechanisms of protective immunity in the 247 residents of a Senegalese village in which malaria is holoendemic. Anopheles gambiae s.l. and An. funestus constituted more than 98% of 11,685 anophelines collected and were present all year round. Inoculation rates of Plasmodium falciparum, P. malariae, and P. ovale averaged respectively 0.51, 0.10, and 0.04 infective bites per person per night. During a four-month period of intensive parasitologic and clinical monitoring, Plasmodium falciparum, P. malariae, and P. ovale were observed in 72.0%, 21.1% and 6.0%, respectively, of the 8,539 thick smears examined. Individual longitudinal data revealed that 98.6% of the villagers harbored trophozoites of P. falciparum at least once during the period of the study. Infections by P. malariae and P. ovale were both observed in individuals of all age groups and their cumulative prevalences reached 50.5% and 40.3%, respectively. Malaria was responsible for 162 (60.9%) of 266 febrile episodes; 159 of these attacks were due to P. falciparum, three to P. ovale, and none to P. malariae. The incidence of malaria attacks was 40 times higher in children 0-4 years of age than in adults more than 40 years old. Our findings suggest that sterile immunity and clinical protection are never fully achieved in humans continuously exposed since birth to intense transmission.

High annual and seasonal variations in malaria transmission by anophelines and vector species composition in Dielmo, a holoendemic area in Senegal.

We conducted a three-year entomologic study in Dielmo, a village of 250 inhabitants in a holoendemic area for malaria in Senegal. Anophelines were captured on human bait and by pyrethrum spray collections. The mosquitoes belonging to the Anopheles gambiae complex were identified using the polymerase chain reaction. Malaria vectors captured were An. funestus, An. arabiensis, and An. gambiae. Anopheles funestus was the most abundant mosquito captured the first year, An. arabiensis in the following years. The annual entomologic inoculation rates calculated by enzyme-linked immunosorbent assay were 238, 89, and 150 for the first, second, and third years, respectively. Each year there was a peak of transmission at the end of the rainy season, but transmission occurred year round. The heterogeneity of transmission was found at four different levels: 1) the relative vector proportion according to the place and method of capture, 2) the human biting rate and relative proportion of vectors by month and year, 3) the infection rate of each vector by year, and 4) the number of infected bites for all vectors, and for each species, for the year. Our data show that even in areas of intense and perennial transmission, there exist large longitudinal variations and strong heterogeneity in entomologic parameters of malaria transmission. It is important to take these into account for the study of the variations in clinical and biological parameters of human malaria, and to evaluate this relationship, a very thorough investigation of transmission is necessary.

Plasmodium ovale in a highly malaria endemic area of Senegal.

During 4 months, from June to September 1990, the population of Dielmo village, Senegal, an area of intense and perennial malaria transmission, was enrolled in a follow-up study including daily clinical surveillance and bi-weekly malaria parasitaemia monitoring. Thick blood film examinations indicated that 48.5% of children (49/101) and 32.4% of adults (34/105) were infected at least once by Plasmodium ovale during the study period; 148 distinct episodes of patent parasitaemia were observed, with estimated maximum durations of 3-115 d. The mean duration at first decreased significantly with age, from 11.4 d in children under 5 years old to 4.2 d in adults aged 40-59 years, but then increased in older adults to 7.0 d. In all age groups, most infections were asymptomatic. Only high parasitaemias were significantly associated with fever; 3 clinical malaria attacks due to P. ovale were seen during the study period.

Malaria: even more chronic in nature than previously thought; evidence for subpatent parasitaemia detectable by the polymerase chain reaction.

In high endemicity areas, malaria is a chronic disease: examination of blood films reveals that up to half of the population, particularly children, harbour parasites at any one given time. The parasitological status of the remainder was addressed using the polymerase chain reaction, a technique 100 to 1000 times more sensitive than microscopy, on a series of samples from Dielmo, a holoendemic area of Senegal. Two-thirds of the microscopically negative individuals were found to harbour subpatent levels of Plasmodium falciparum, suggesting that more than 90% of the exposed population at any one time, i.e. in a cross-sectional survey, are chronically infected. This also means that the range of parasite loads harboured by humans with various degrees of exposure is remarkably large, probably reflecting a large range of effectiveness of the defence mechanisms against malaria parasites, none of which is fully efficient.

Variation of Plasmodium falciparum msp1 block 2 and msp2 allele prevalence and of infection complexity in two neighbouring Senegalese villages with different transmission conditions.

To investigate the impact of transmission on the development of immunity to malaria and on parasite diversity, longitudinal surveys have been conducted for several years in Dielmo and Ndiop, 2 neighbouring Senegalese villages with holo- and mesoendemic transmission conditions, respectively. We analysed Plasmodium falciparum msp1 block 2 and msp2 genotypes of isolates collected from 58% of the Dielmo villagers during the same week as those studied recently from Ndiop. Allele frequencies differed in both villages, indicating considerable microgeographical heterogeneity of parasite populations. The complexity of the infections, estimated using individual or combined msp1 and msp2 genotyping, in Dielmo was more than double that in Ndiop and it was age-dependent in Dielmo but not in Ndiop. Thus, this study confirmed the influence of age on the complexity of asymptomatic malaria infections in a holoendemic area. The age distribution of complexity in Dielmo substantiates the interpretation that the number of parasite types per isolate reflects acquired antiparasite immunity. This cross-sectional survey also confirms that the sickle cell trait has no impact on complexity but influences the distribution of P. falciparum genotypes.

Indoor resting by outdoor biting females of Anopheles gambiae complex (Diptera:Culicidae) in the Sahel of northern Senegal.

Three villages in the Senegal River basin were selected to study the biting and resting behavior of Anopheles gambiae s.l. in relation to human habits, rainfalls, and rice culture irrigation. All inhabitants sleep outside throughout the year, mainly under poor quality bednets. Mosquitoes were collected host-seeking during the night on human bait outside and resting during the day inside and outside in pit shelters. An. gambiae s.s. and An. arabiensis fed mainly outside, the only place where hosts are available; fed and gravid females resting indoors fed outside. The proportions of An. gambiae s.s. and An. arabiensis in outdoor biting catches and in indoor spray catches were not significantly different, but they differed from year to year with the latter sampling method, An. gambiae s.s. predominated in 1990, a more wet and humid year, whereas An. arabiensis was more common in 1991, which was an arid year. Both species are highly endophilic in this arid area where outdoor-resting places are limited.

[Biology of the vectors and transmission of Plasmodium falciparum, P. malariae and P. ovale in a village in the savanna of west Africa (Dielmo, Senegal)]. / Biologie des vecteurs et transmission de Plasmodium falciparum, P. malariae et P. ovale dans un village de savane d'afrique de l'ouest (Dielmo, Sénégal).

From April 1990 to March 1992 a longitudinal entomological study was carried out in Dielmo village, Senegal, an area of Sudan-type savanna. Mosquitoes were sampled by night-bite collections and pyretnrum spray collections. Seven anopheles species were identified: An. gambiae s.s. An. arabiensis, An. funestus, An. pharoensis, An. rufipes, An. squamosus and An. ziemanni. Present throughout the year, An. gambiae s.l. and An. funestus represented more than 98% of anopheles captured on man. A yearly wave of An. gambiae s.l. was observed in the rainy season and An. funestus was generally more abundant in the dry season. The sporozoite rate was 1.5% and 1.3%, respectively, for these two species. Sporozoite typing by monoclonal antibodies indicated that the proportion of infected salivary glands was 92.7% P. falciparum, 18.2% P malariae and 8.2% P. ovale. The inoculation rate was calculated to be respectively 111, 21 and 8 infective bites per human for P. falciparum, P. malariae and P. ovale during the first year. Transmission was highest in the second year, with respectively 272, 54 and 25 infective bites per human.