Diversity in anopheline larval habitats and adult composition during the dry and wet seasons in Ouagadougou (Burkina Faso)

Background: Several cases of malaria are frequently recorded during the dry period in Ouagadougou town (Burkina Faso). This has led to the design of a series of studies focusing on both parasitological and entomological investigations intended to provide relevant health data on the risk of local malaria transmission according to the way of urbanisation. Methods: A cross-sectional entomological survey was carried out in various districts of Ouagadougou in April and October 2006. Adult malaria vectors were collected using CDC traps and indoor insecticide spraying performed in four houses during four consecutive days/nights. Intensive larval sampling was also done in available water ponds throughout the study sites. Results: In April, the anopheline breeding sites consisted only of semi-permanent or permanent swamps located mainly in the two peripheral districts. Despite the presence of anopheline larvae in these breeding sites, less than five Anopheles gambiae s.l. adults were caught by CDC traps and indoor insecticide spraying. In October, additionally to the permanent breeding sites reported in April, some rainfall swamps were also found positive to anophelines. The number of adults' mosquitoes was higher than that collected in April (2 vs 159 in October). Out of 115 larvae of An. gambiae s.l. analysed by PCR in April, 59.1% (68/115) were identified as Anopheles arabiensis, 39.1% (45/115) as An. gambiae M while the S form represented less than 2%. Overall 120 larvae and 86 females were identified by PCR in October as An. gambiae M form (51%) and An. arabiensis (42.2%). The S form represented only 6.8%. The global sporozoite rate recorded was high (6.8%) and did not differ between the districts except in the central district where no positive mosquito was detected. Conclusion: Although only few adults' mosquitoes were actively caught during the driest month, malaria vectors persisted all year long that increases the risk of urban malaria transmission. The distribution of breeding sites and especially the occurrence of malaria vectors were more abundant in the periphery, which is more like that of a rural settlement. The evolution of malaria prevalence and the factors sustaining the risk of transmission in Ouagadougou as well in many African cities during the dry season are discussed

Beer Consumption Increases Human Attractiveness to Malaria Mosquitoes

Background: Malaria and alcohol consumption both represent major public health problems. Alcohol consumption is rising in developing countries and, as efforts to manage malaria are expanded, understanding the links between malaria and alcohol consumption becomes crucial. Our aim was to ascertain the effect of beer consumption on human attractiveness to malaria mosquitoes in semi field conditions in Burkina Faso. Methodology/Principal Findings: We used a Y tube-olfactometer designed to take advantage of the whole body odour (breath and skin emanations) as a stimulus to gauge human attractiveness to Anopheles gambiae (the primary African malaria vector) before and after volunteers consumed either beer (n = 25 volunteers and a total of 2500 mosquitoes tested) or water (n = 18 volunteers and a total of 1800 mosquitoes). Water consumption had no effect on human attractiveness to An. gambiae mosquitoes, but beer consumption increased volunteer attractiveness. Body odours of volunteers who consumed beer increased mosquito activation (proportion of mosquitoes engaging in take-off and up-wind flight) and orientation (proportion of mosquitoes flying towards volunteers' odours). The level of exhaled carbon dioxide and body temperature had no effect on human attractiveness to mosquitoes. Despite individual volunteer variation, beer consumption consistently increased attractiveness to mosquitoes. Conclusions/Significance: These results suggest that beer consumption is a risk factor for malaria and needs to be integrated into public health policies for the design of control measures

Plant-mediated effects on mosquito capacity to transmit human malaria

The ecological context in which mosquitoes and malaria parasites interact has received little attention, compared to the genetic and molecular aspects of malaria transmission. Plant nectar and fruits are important for the nutritional ecology of malaria vectors, but how the natural diversity of plant-derived sugar sources affects mosquito competence for malaria parasites is unclear. To test this, we infected Anopheles coluzzi, an important African malaria vector, with sympatric field isolates of Plasmodium falciparum, using direct membrane feeding assays. Through a series of experiments, we then examined the effects of sugar meals from Thevetia neriifolia and Barleria lupilina cuttings that included flowers, and fruit from Lannea microcarpa and Mangifera indica on parasite and mosquito traits that are key for determining the intensity of malaria transmission. We found that the source of plant sugar meal differentially affected infection prevalence and intensity, the development duration of the parasites, as well as the survival and fecundity of the vector. These effects are likely the result of complex interactions between toxic secondary metabolites and the nutritional quality of the plant sugar source, as well as of host resource availability and parasite growth. Using an epidemiological model, we show that plant sugar source can be a significant driver of malaria transmission dynamics, with some plant species exhibiting either transmission-reducing or -enhancing activities

Rémanence de la deltaméthrine en imprégnation de tulle moustiquaire dans les conditions naturelles d'utilisation

revue scientifiqueLa rémanence de Ia deltaméthrine, appliquée à la concentration de 25 mg/m2, en imprégnatioin de tulle moustiquaire a été étudiée dans des conditions naturelles d'utilisation. Les temps d'apparition de l'effet "knock down" d'une population d'Anopheles gambiae d'élevage, ont été utilisés comme reflet de Ia rémanence de l'insecticide. Les temps Kd 95% moyens ont éfé inférieurs à 20 minutes, correspondant à ceux d'une imprégnation récente, pendant les sept premiers mois d'utilisation de la moustiquaire. Apparemment, il n'y aurait pas de relation directement proportionnelle entre la concentration résiduelle en insecticide sur le tulle moustiquaire et l'allongement des temps Kd

Technique de l'insecte stérile à la Réunion : comprendre le fonctionnement de la cible : Aedes albopictus [poster]

International audienceContexte • Le principe de la Technique de l'insecte stérile (TIS) est de lâcher des moustiques mâles élevés en masse et rendus stériles par irradiation. • L'accouplement des moustiques mâles stériles avec les moustiques femelles ne donne pas de descendant. • La TIS présente de nombreux avantages dont notamment le fait qu'elle est écologique et ne cible que l'espèce qu'on veut combattre (pas d'effets collatéraux sur les autres espèces ou organismes non cibles); elle permet de s'affranchir à terme de l'utilisation d'insecticides et peut conduire à la suppression de certaines populations de moustiques. 1. Etude du comportement sexuel des mâles stériles et non stériles Objectif: Evaluer l'effet de l'irradiation sur 1) la capacité d'accouplement (Fig. 1), la longévité (Fig. 2) le cycle d'activité (Fig. 3.) la compétition pour l'accouplement (Fig.4) 2. Etude de la dynamique des populations d'Aedes albopictus à la Réunion Objectifs scientifiques • Chez les moustiques, seules les femelles piquent. Dans une intervention par la TIS, un grand nombre de mâles (qui ne piquent pas) doit être relâché. • La réalisation de la TIS nécessite au préalable de connaître la biologie et surtout le comportement sexuel des moustiques dans la natures, mais également l'effet de la stérilisation sur le comportement des mâles stérilisés. Partenaires Fig. 1: Capacité sexuelle des mâles stériles et non stériles Fig. 2: longévité des mâles stériles et non stériles Pas d'effet de l'irradiation sur la survie Même capacité sexuelle des mâles stériles et non stériles la première semaine après l'irradiation.-moustiques mâles stériles sexuellement aussi compétitifs que les mâles non stériles;-la TIS est plus efficace quand le nombre de mâles stériles est 5 à 10 fois supérieur au nombre mâles non stériles Fig. 4: Compétitivité sexuelle entre mâles stériles et non stériles Fig. 3: cycle d'activité des mâles stériles et non stériles Conclusion générale Les preuves scientifiques de l'efficacité de la TIS sont réunies, mais des efforts sont nécessaires pour démontrer son efficacité sur le terrain à l'île de la Réunion. • Les informations recueillies sur la biologie du moustique tigre permettent de cibler le moment de l'intervention et d'évaluer l'efficacité de la TIS Suivi vidéo au laboratoire: deux pics d'activité même rythme d'activité chez les mâles irradiés et non irradiés La stérilisation des moustiques se fait par irradiation aux rayons gamma (Caesium 137) Diminution de la fertilité des femelles de > 95% lorsqu'elles s'accouplent avec les mâles stérilisés à 35-40 Gy en 15 minutes Aedes albopictus mâle et femelle Nymples Adulte

Technique de l'Insecte Stérile à La Réunion. Comprendre le comportement de la cible: Aedes albopictus

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