ABSTRACT
Malaria, a major cause of child mortality in Africa, is engendered by Plasmodium parasites that are transmitted by anopheline mosquitoes. Fitness of Plasmodium parasites is closely linked to the ecology and evolution of its anopheline vector. However, whether the genetic structure of vector populations impacts malaria transmission remains unknown. Here, we describe a partitioning of the African malaria vectors into generalists and specialists that evolve along ecological boundaries. We next identify the contribution of mosquito species to Plasmodium abundance using Granger causality tests for time-series data collected over two rainy seasons in Mali. We find that mosquito microevolution, defined by changes in the genetic structure of a population over short ecological timescales, drives Plasmodium dynamics in nature, whereas vector abundance, infection prevalence, temperature and rain have low predictive values. Our study demonstrates the power of time-series approaches in vector biology and highlights the importance of focusing local vector control strategies on mosquito species that drive malaria dynamics.
Subject(s)
Evolution, Molecular , Mosquito Vectors/genetics , Mosquito Vectors/parasitology , Plasmodium falciparum/physiology , Animals , Anopheles/genetics , Ecosystem , Genotype , Humans , Insect Proteins/genetics , Malaria/epidemiology , Malaria/transmission , Mali , Prevalence , Rain , Seasons , Species Specificity , TemperatureABSTRACT
Numerous studies have shown the influence of some bacteria colonizing the breeding sites on the development of the parasite in Anopheles malaria vectors. The aim of this study was to evaluate the impact of the breeding sites of Plasmodium falciparum on the gametocytes infectivity of Anopheles gambiae sl using the membrane feeding method. We carried out an experimental infestation study from September 2010 to January 2011 in a village located in the southern savanna of Mali. Cross sectional surveys were conducted to collect larvae and to select gametocyte carriers. Female offspring of L3 and L4 stage larvae were used for the experimental infestation. The gametocyte carriers were children aged within 4 to 12 years. Bacteria identified in breeding water of larvae and adult mosquitoes were: Escherichia coli, Salmonella spp, Klebsiella oxytoca, Pseudomonas spp, Staphylococcus spp, Shigella sp. The oocyst load of infected mosquitoes did not significantly vary according to the samples (F = 1.517, P = 0.230). Low infection rates (5.4% and 2.8%) were observed in the larval bedding and in mosquitoes containing K. oxytoca and Shigella. The blood feeding rates (62.4%; 60.9%; 67.7%) and mortality (66.4%; 64.9%; 61.9%) of An. gambiae did not significantly vary depending on the breeding sites [(P = 0.15); (P = 0.22)].
De nombreuses études ont montré l'influence de certaines bactéries vivant dans les gites larvaires sur le développement du parasite chez les anophèles vecteurs du paludisme. Le but du présent travail consistait à étudier l'impact des gites larvaires sur l'infectivité des gamétocytes de Plasmodium falciparum chez Anopheles gambiae s.l par la technique d'infestation sur membrane. Pour réaliser ce travail, une étude d'infestation expérimentale a été conduite de septembre 2010 à janvier 2011 dans un village de savane sud soudanienne du Mali. Des passages transversaux ont été effectués pour la collecte des larves et la sélection des porteurs de gamétocytes. Les femelles issues des larves de stades L3 et L4 ont été utilisées pour les séances d'infestation expérimentale. Les enfants porteurs de gamétocytes étaient âgés de 4 à 12 ans. Les bactéries identifiées dans l'eau des gites chez les larves et les adultes de moustiques étaient : Escherichia coli, Salmonella s.p., Klebsiella oxytoca, Pseudomonas s.p., Staphylococcus s.p., Shigella sp. La charge oocystique des moustiques infectés n'avait pas varié de façon significative en fonction des gites (F=1,517 ; P=0,230). De faibles taux d'infection (5,4% et 2,8%) ont été observés dans les gites et chez les moustiques contenant K. oxytoca et Shigella. Le taux d'engorgement (62,4% ; 60,9% ; 67,7%) et le taux de mortalité (66,4% ; 64,9% ; 61,9%) d'An. gambiae n'ont pas varié significativement en fonction des gites larvaires,[(P= 0,15) ; (P= 0,22)].
