Hydric stress-dependent effects of Plasmodium falciparum infection on the survival of wild-caught Anopheles gambiae female mosquitoes

<p>Abstract</p> <p>Background</p> <p>Whether <it>Plasmodium falciparum</it>, the agent of human malaria responsible for over a million deaths per year, causes fitness costs in its mosquito vectors is a burning question that has not yet been adequately resolved. Understanding the evolutionary forces responsible for the maintenance of susceptibility and refractory alleles in natural mosquito populations is critical for understanding malaria transmission dynamics.</p> <p>Methods</p> <p>In natural mosquito populations, <it>Plasmodium </it>fitness costs may only be expressed in combination with other environmental stress factors hence this hypothesis was tested experimentally. Wild-caught blood-fed <it>Anopheles gambiae </it>s.s. females of the M and S molecular form from an area endemic for malaria in Mali, West Africa, were brought to the laboratory and submitted to a 7-day period of mild hydric stress or kept with water ad-libitum. At the end of this experiment all females were submitted to intense desiccation until death. The survival of all females throughout both stress episodes, as well as their body size and infection status was recorded. The importance of stress, body size and molecular form on infection prevalence and female survival was investigated using Logistic Regression and Proportional-Hazard analysis.</p> <p>Results</p> <p>Females subjected to mild stress exhibited patterns of survival and prevalence of infection compatible with increased parasite-induced mortality compared to non-stressed females. Fitness costs seemed to be linked to ookinetes and early oocyst development but not the presence of sporozoites. In addition, when females were subjected to intense desiccation stress, those carrying oocysts exhibited drastically reduced survival but those carrying sporozoites were unaffected. No significant differences in prevalence of infection and infection-induced mortality were found between the M and S molecular forms of <it>Anopheles gambiae</it>.</p> <p>Conclusions</p> <p>Because these results suggest that infected mosquitoes may incur fitness costs under natural-like conditions, they are particularly relevant to vector control strategies aiming at boosting naturally occurring refractoriness or spreading natural or foreign genes for refractoriness using genetic drive systems in vector populations.</p

Hydric stress-dependent effects of Plasmodium falciparum infection on the survival of wild-caught Anopheles gambiae female mosquitoes

<p>Abstract</p> <p>Background</p> <p>Whether <it>Plasmodium falciparum</it>, the agent of human malaria responsible for over a million deaths per year, causes fitness costs in its mosquito vectors is a burning question that has not yet been adequately resolved. Understanding the evolutionary forces responsible for the maintenance of susceptibility and refractory alleles in natural mosquito populations is critical for understanding malaria transmission dynamics.</p> <p>Methods</p> <p>In natural mosquito populations, <it>Plasmodium </it>fitness costs may only be expressed in combination with other environmental stress factors hence this hypothesis was tested experimentally. Wild-caught blood-fed <it>Anopheles gambiae </it>s.s. females of the M and S molecular form from an area endemic for malaria in Mali, West Africa, were brought to the laboratory and submitted to a 7-day period of mild hydric stress or kept with water ad-libitum. At the end of this experiment all females were submitted to intense desiccation until death. The survival of all females throughout both stress episodes, as well as their body size and infection status was recorded. The importance of stress, body size and molecular form on infection prevalence and female survival was investigated using Logistic Regression and Proportional-Hazard analysis.</p> <p>Results</p> <p>Females subjected to mild stress exhibited patterns of survival and prevalence of infection compatible with increased parasite-induced mortality compared to non-stressed females. Fitness costs seemed to be linked to ookinetes and early oocyst development but not the presence of sporozoites. In addition, when females were subjected to intense desiccation stress, those carrying oocysts exhibited drastically reduced survival but those carrying sporozoites were unaffected. No significant differences in prevalence of infection and infection-induced mortality were found between the M and S molecular forms of <it>Anopheles gambiae</it>.</p> <p>Conclusions</p> <p>Because these results suggest that infected mosquitoes may incur fitness costs under natural-like conditions, they are particularly relevant to vector control strategies aiming at boosting naturally occurring refractoriness or spreading natural or foreign genes for refractoriness using genetic drive systems in vector populations.</p

Efficacy of Artesunate + Sulfamethoxypyrazine/Pyrimethamine versus Praziquantel in the Treatment of Schistosoma haematobium in Children

BACKGROUND:This study was conducted to determine the efficacy of the antimalarial artemisinin-based combination therapy (ACT) artesunate +sulfamethoxypyrazine/pyrimethamine (As+SMP), administered in doses used for malaria, to treat Schistosoma haematobium in school aged children. METHODOLOGY/PRINCIPAL FINDINGS:The study was conducted in Djalakorodji, a peri-urban area of Bamako, Mali, using a double blind setup in which As+SMP was compared with praziquantel (PZQ). Urine samples were examined for Schistosoma haematobium on days -1, 0, 28 and 29. Detection of haematuria, and haematological and biochemical exams were conducted on day 0 and day 28. Clinical exams were performed on days 0, 1, 2, and 28. A total of 800 children were included in the trial. The cure rate obtained without viability testing was 43.9% in the As+SMP group versus 53% in the PZQ group (Chi(2) = 6.44, p = 0.011). Egg reduction rates were 95.6% with PZQ in comparison with 92.8% with As+SMP, p = 0.096. The proportion of participants who experienced adverse events related to the medication was 0.5% (2/400) in As+SMP treated children compared to 2.3% (9/399) in the PZQ group (p = 0.033). Abdominal pain and vomiting were the most frequent adverse events in both treatment arms. All adverse events were categorized as mild. CONCLUSIONS/SIGNIFICANCE:The study demonstrates that PZQ was more effective than As+SMP for treating Schistosoma haematobium. However, the safety and tolerability profile of As+SMP was similar to that seen with PZQ. Our findings suggest that further investigations seem justifiable to determine the dose/efficacy/safety pattern of As+SMP in the treatment of Schistosoma infections. TRIAL REGISTRATION:ClinicalTrials.gov NCT00510159

Résumé des résultats des enquêtes de base niveau ménage : site de Tougou, Burkina Faso

Ce rapport présente les résultats des enquêtes de base conduites au niveau des ménages de sept (7) villages du site de Tougou (Burkina Faso) dans le cadre du programme de recherche du CGIAR sur le Changement Climatique, l’Agriculture et la Sécurité Alimentaire. L’objectif de ces enquêtes était de de collecter toutes les données et informations sur des indicateurs clés de base concernant les ménages notamment les moyens de subsistance, l’agriculture et la gestion des ressources naturelles, les besoins d’information sur le climat et la gestion des risques, et les pratiques d’atténuation et d’adaptation

Résumé des résultats des enquêtes de base niveau ménage : site de Cinzana, Mali Décembre 2011 L. Diakité, K. Sissoko, R. Zougmoré, B. Traoré, M. Amadou, A.S. Moussa, W. Forch,

Ce rapport présente les résultats des enquêtes de base conduites au niveau des ménages de sept villages du site de Cinzana (région de Ségou, Mali) dans le cadre du programme de recherche du CGIAR sur le Changement Climatique, l’Agriculture et la Sécurité Alimentaire. L’objectif de ces enquêtes était de de collecter toutes les données et informations sur des indicateurs clés de base concernant les ménages notamment les moyens de subsistance, l’agriculture et la gestion des ressources naturelles, les besoins d’information sur le climat et la gestion des risques, et les pratiques d’atténuation et d’adaptation

Geostatistical Model-Based Estimates of Schistosomiasis Prevalence among Individuals Aged ≤20 Years in West Africa

Schistosomiasis is a parasitic disease caused by a blood fluke that mainly occurs in Africa. Current prevalence estimates of schistosomiasis are based on historical data, and hence might be outdated due to control programs, improved sanitation, and water resources development and management (e.g., construction of large dams and irrigation systems). To help planning, coordination, and evaluation of control activities, reliable schistosomiasis prevalence estimates are needed. We analyzed compiled survey data from 1980 onwards for West Africa, including Cameroon, focusing on individuals aged ≤20 years. Bayesian geostatistical models were implemented based on environmental and climatic predictors to take into account potential spatial clustering within the data. We created the first smooth data-driven prevalence maps for Schistosoma mansoni and S. haematobium at high spatial resolution throughout West Africa. We found that an estimated 50.8 million West Africans aged ≤20 years are infected with schistosome blood flukes. Country prevalence estimates ranged between 0.5% (in The Gambia) and 37.1% (in Liberia) for S. mansoni and between 17.6% (in The Gambia) and 51.6% (in Sierra Leone) for S. haematobium. Our results allow prioritization of areas where interventions are needed, and to monitor and evaluate the impact of control activities

Résumé des résultats des enquêtes de base niveau ménage: site de Lawra-Jirapa, Ghana

Ce rapport présente les résultats des enquêtes de base conduites au niveau des ménages du site de Lawra-Jirapa au Ghana dans le cadre du programme de recherche du CGIAR sur le Changement Climatique, l’Agriculture et la Sécurité Alimentaire. L’objectif de ces enquêtes était de de collecter toutes les données et informations sur des indicateurs clés de base concernant les ménages notamment les moyens de subsistance, l’agriculture et la gestion des ressources naturelles, les besoins d’information sur le climat et la gestion des risques, et les pratiques d’atténuation et d’adaptation. L’agriculture demeure la principale activité économique de la plus part des ménages. La production céréalière et des tubercules/maraichage est très importante. L’élevage contribue aussi fortement à la satisfaction des besoins alimentaires et moyens de subsistance des ménages. La production agricole est très diversifiée avec environ 82% des ménages qui cultivent/produisent plus de 7 cultures. La grande partie de la production aussi bien au sein qu’en dehors de l’exploitation agricole est destinée essentiellement à l’autoconsommation du ménage. Seulement 4% des ménages ont déclaré être « auto-suffisants » toute l’année, alors que 26,4% sont en situation d’insécurité alimentaire pendant presque la moitié de l’année. Plus de 97% des ménages détiennent des terres de plus de 5ha alors que 3% ont indiqué posséder entre 1-5ha. Environ 91,4% des ménages enquêtés n’utilisent que la pluie comme source d’eau pour l’agriculture. Seulement 4% de ces ménages utilisent d’autres sources telles que les forages et barrages. Environ 31% ont indiqué recourir aux intrants agricoles, notamment les engrais et pesticides. Les emplois sur d’autres exploitations, le petit commerce et les transferts/dons sont les principales sources de revenus des ménages. Les ménages ont indiqué plusieurs changements intervenus dans les systèmes de production agricole et animale au cours des dix dernières années. Ces changements ont été induits par plusieurs facteurs parmi lesquels les marchés, le changement de climat, les maladies et ravageurs et les influences des projets et ONG. Plus de la moitié des ménages (87%) ont indiqué avoir reçu des informations sur le climat et la météorologie, parmi lesquelles les plus importantes sont les prévisions sur les événements extrêmes, prévisions sur le début de la saison des pluies et prévisions sur les prochains 2-3 mois. Ces informations obtenues principalement à travers la radio sont souvent accompagnées de conseils que les ménages ont indiqué suivre et prendre en compte dans la prise de décision concernant les activités de production végétale et animale et la gestion de l’exploitation en général. Les groupes épargne et crédit, amélioration de la productivité sont les plus importants avec respectivement 23,7% et 21,7% des ménages qui ont indiqué avoir des membres affiliés à ces groupes. La radio demeure la principale source d’information. La possession de bien est limitée au minimum de base (55% des ménages) et aussi le niveau intermédiaire (44% des ménages)