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Fossog Tene B.,Laboratoire Of Recherche Sur Le Paludisme | Fossog Tene B.,University of Yaounde I | Costantini C.,Montpellier University | Awono-Ambene P.,Laboratoire Of Recherche Sur Le Paludisme | Antonio-Nkondjio C.,Laboratoire Of Recherche Sur Le Paludisme
PLoS ONE | Year: 2013

Background: In the city of Yaoundé in Cameroon malaria is predominately transmitted by the M and S molecular forms of Anopheles gambiae and both are resistant to the pyrethroid insecticides and DDT. Mutations in the target site of these insecticides, present at a high frequency in malaria vectors in this city, contribute to this resistance profile. To identify additional resistance mechanisms, the expression profile of multiple DDT-resistant field populations of M and S molecular forms was compared to laboratory-susceptible populations. Methodology/Principal findings: The prevalence of DDT resistance was highest in the S form population originating from the cultivated site of Nkolondom (mortality after WHO bioassay = 4%). A high prevalence of DDT resistance was also found in two urban M form populations, Messa from a pristine unpolluted environment (DDT mortality = 54%), and Gare, where the breeding sites are heavily polluted with organic matter (DDT mortality = 38%). Microarray analysis showed that several transcripts coding for detoxification enzymes (P450s, GSTs and UDPGTs) and ABC transporters were upregulated in the three populations. Despite the presence of multiple detoxification genes over expressed in the DDT-resistant subset of these field populations, only three were commonly over expressed in resistant populations from all three environments. Two of these genes, CYP6M2 and GSTD1-6, encode enzymes that have been previously shown to metabolize DDT. Conclusion/Significance: Analogous to target site resistance, genes involved in metabolic resistance to DDT are also shared between the M and S forms of An gambiae. Alternative explanations for this occurrence are explored. © 2013 Fossog Tene et al.


Cassone B.J.,University of Notre Dame | Cassone B.J.,Ohio State University | Kamdem C.,Laboratoire Of Recherche Sur Le Paludisme | Kamdem C.,University of California at Riverside | And 6 more authors.
Molecular Ecology | Year: 2014

Divergent selection based on aquatic larval ecology is a likely factor in the recent isolation of two broadly sympatric and morphologically identical African mosquito species, the malaria vectors Anopheles gambiae and An. coluzzii. Population-based genome scans have revealed numerous candidate regions of recent positive selection, but have provided few clues as to the genetic mechanisms underlying behavioural and physiological divergence between the two species, phenotypes which themselves remain obscure. To uncover possible genetic mechanisms, we compared global transcriptional profiles of natural and experimental populations using gene-based microarrays. Larvae were sampled as second and fourth instars from natural populations in and around the city of Yaoundé, capital of Cameroon, where the two species segregate along a gradient of urbanization. Functional enrichment analysis of differentially expressed genes revealed that An. coluzzii - the species that breeds in more stable, biotically complex and potentially polluted urban water bodies - overexpresses genes implicated in detoxification and immunity relative to An. gambiae, which breeds in more ephemeral and relatively depauperate pools and puddles in suburbs and rural areas. Moreover, our data suggest that such overexpression by An. coluzzii is not a transient result of induction by xenobiotics in the larval habitat, but an inherent and presumably adaptive response to repeatedly encountered environmental stressors. Finally, we find no significant overlap between the differentially expressed loci and previously identified genomic regions of recent positive selection, suggesting that transcriptome divergence is regulated by trans-acting factors rather than cis-acting elements. © 2014 John Wiley & Sons Ltd.


Foumane Ngane V.,Laboratoire Of Recherche Sur Le Paludisme | Allico Djaman J.,Félix Houphouët-Boigny University | Culeux C.,University of Paris Descartes | Piette N.,University of Paris Descartes | And 5 more authors.
Malaria Journal | Year: 2015

Background: The malaria situation has been worsening in Angola, partly due to armed conflict until the recent past and drug-resistant Plasmodium falciparum. Malaria transmission is heterogeneous within the country, and data on drug-resistant malaria in different parts of the country are incomplete. The aim of the present study was to evaluate resistance to 4-aminoquinolines and antifolate drugs in P. falciparum isolates collected in Benguela province, central Angola, using molecular markers. Methods: Fingerprick capillary blood was collected from asymptomatic children aged less than 15 years old during a household survey in and around Balombo town in 2010-2011. Samples were screened for P. falciparum by nested PCR. Molecular markers (P. falciparum dihydrofolate reductase [pfdhfr], P. falciparum dihydropteroate synthase [pfdhps], P. falciparum chloroquine resistance transporter [pfcrt], and P. falciparum multidrug-resistance gene 1 [pfmdr1]) were sequenced to determine the key codons associated with drug resistance. Results: A total of 60 blood samples were positive for P. falciparum. Most isolates with successful PCR amplification had mutant pfdhfr alleles, with either double mutant AICNI (69%) or triple mutant AIRNI (21%) haplotypes. A16V, S108T, and I164L substitutions were not found. Many of the isolates were carriers of either SGKAA (60%) or AGKAA (27%) pfdhps haplotype. K540E substitution was absent. There were only two pfcrt haplotypes: wild-type CVMNK (11%) and mutant CVIET (89%). Wild-type pfmdr1 NYSND haplotype was found in 19% of the isolates, whereas single mutant pfmdr1 YYSND and NFSND haplotypes occurred in 48% and 11%, respectively. Double mutant pfmdr1 haplotypes (YFSND and YYSNY) occurred rarely. Conclusions: The results suggest that the high prevalence of mutant pfcrt CVIET haplotype is in agreement with low clinical efficacy of chloroquine observed in earlier studies and that the double pfdhfr mutant AICNI and single pfdhps mutant SGKAA are currently the predominant haplotypes associated with antifolate resistance in Benguela province. The hallmark of clinical resistance observed in East Africa, i.e. triple pfdhfr mutant haplotype (AIRNI) and double pfdhps mutant haplotype (SGEAA), was absent. These molecular findings need to be further evaluated in parallel with clinical studies, in particular with the efficacy of intermittent preventive treatment using sulphadoxine-pyrimethamine in pregnant women and artesunate-amodiaquine for uncomplicated malaria. © 2015 Foumane Ngane et al.; licensee BioMed Central.


Reidenbach K.R.,University of Notre Dame | Neafsey D.E.,Cambridge Broad Institute | Costantini C.,IRD Montpellier | Costantini C.,Laboratoire Of Recherche Sur Le Paludisme | And 9 more authors.
Genome Biology and Evolution | Year: 2012

Anopheles gambiae M and S are thought to be undergoing ecological speciation by adapting to different larval habitats. Toward an improved understanding of the genetic determinants and evolutionary processes shaping their divergence, we used a 400,000 single-nucleotide polymorphism(SNP) genotyping array to characterize patterns of genomic differentiation between four geographically paired M and S population samples from West and Central Africa. In keeping with recent studies based on more limited genomic or geographic sampling, divergence was not confined to a few isolated "speciation islands." Divergence was both widespread across the genome and heterogeneous. Moreover, we find consistent patterns of genomic divergence across sampling sites and mutually exclusive clustering of M and S populations using genetic distances based on all 400,000 SNPs, implying that M and S are evolving collectively across the study area. Nevertheless, the clustering of local M and Spopulations using genetic distances based on SNPs from genomic regions of low differentiation is consistent with recent gene flow and introgression. To account for these data and reconcile apparent paradoxes in reported patterns of M-S genomic divergence and hybridization, we propose that extrinsic ecologically based postmating barriers vary in strength as environmental conditions fluctuate or change. © 2012 The Author(s).


Kamgang B.,IRD Montpellier | Kamgang B.,Laboratoire Of Recherche Sur Le Paludisme | Brengues C.,IRD Montpellier | Fontenille D.,IRD Montpellier | And 5 more authors.
PLoS ONE | Year: 2011

Background: Aedes albopictus (Skuse, 1884) (Diptera: Culicidae), a mosquito native to Asia, has recently invaded all five continents. In Central Africa it was first reported in the early 2000s, and has since been implicated in the emergence of arboviruses such as dengue and chikungunya in this region. Recent genetic studies of invasive species have shown that multiple introductions are a key factor for successful expansion in new areas. As a result, phenotypic characters such as vector competence and insecticide susceptibility may vary within invasive pest species, potentially affecting vector efficiency and pest management. Here we assessed the genetic variability and population genetics of Ae. albopictus isolates in Cameroon (Central Africa), thereby deducing their likely geographic origin. Methods and Results: Mosquitoes were sampled in 2007 in 12 localities in southern Cameroon and analyzed for polymorphism at six microsatellite loci and in two mitochondrial DNA regions (ND5 and COI). All the microsatellite markers were successfully amplified and were polymorphic, showing moderate genetic structureamong geographic populations (FST = 0.068, P<0.0001). Analysis of mtDNA sequences revealed four haplotypes each for the COI and ND5 genes, with a dominant haplotype shared by all Cameroonian samples. The weak genetic variation estimated from the mtDNA genes is consistent with the recent arrival of Ae. albopictus in Cameroon. Phylogeographic analysis based on COI polymorphism indicated that Ae. albopictus populations from Cameroon are related to tropical rather than temperate or subtropical outgroups. Conclusion: The moderate genetic diversity observed among Cameroonian Ae. albopictus isolates is in keeping with recent introduction and spread in this country. The genetic structure of natural populations points to multiple introductions from tropical regions. © 2011 Kamgang et al.


Kamgang B.,IRD Montpellier | Kamgang B.,Laboratoire Of Recherche Sur Le Paludisme | Kamgang B.,Institute Pasteur Of Bangui | Nchoutpouen E.,IRD Montpellier | And 3 more authors.
Parasites and Vectors | Year: 2012

Background: The invasive mosquito Aedes albopictus is often considered a poor vector of human pathogens, owing to its catholic feeding behavior. However, it was recently incriminated as a major vector in several Chikungunya epidemics, outside of its native range. Here we assessed two key elements of feeding behavior by Ae. albopictus females in Yaoundé, Cameroon, Central Africa. Host preference was explored and the human-biting activity of females was monitored over 24 h to determine periods of maximum bite exposure. Findings. Analysis of ingested blood in outdoor-resting females showed that Ae. albopictus preferentially fed on humans rather than on available domestic animals (95% of the blood meals contained human blood). Our results further showed that Ae. albopictus is a day-biting species in Yaoundé, with a main peak of activity in the late afternoon. Conclusion: This is the first report on the feeding behavior of Ae. albopictus in Central Africa. The species is highly aggressive to humans and might therefore be involved in human-human virus transmission in this setting. © 2012 Kamgang et al; licensee BioMed Central Ltd.


PubMed | World Health Organization, WHO country Office in Cameroon, University of Yaounde I, Ministry of Public Health and 2 more.
Type: Journal Article | Journal: Parasites & vectors | Year: 2017

As part of a study to determine the impact of insecticide resistance on the effectiveness of long-lasting insecticide treated nets (LLINs) in the north of Cameroon, the unexpectedly high density and anthropophilic behaviour of Anopheles rufipes lead us to investigate this species bionomics and role in human malaria parasite transmission.For four consecutive years (2011-2014), annual cross-sectional sampling of adult mosquitoes was conducted during the peak malaria season (September-October) in three health districts in northern Cameroon. Mosquitoes sampled by human landing catch and pyrethrum spray catch methods were morphologically identified, their ovaries dissected for parity determination and Anopheles gambiae siblings were identified by molecular assay. Infection with P. falciparum and blood meal source in residual fauna of indoor resting anopheline mosquitoes were determined by enzyme-linked-immunosorbent assays.Anopheles gambiae (sensu lato)(s.l.) comprised 18.4% of mosquitoes collected with An. arabiensis representing 66.27% of the sibling species. The proportion of An. rufipes (2.7%) collected was high with a human-biting rate ranging between 0.441 and 11.083 bites/person/night (b/p/n) and an anthropophagic rate of 15.36%. Although overall the members of An. gambiae complex were responsible for most of the transmission with entomological inoculation rates (EIR) reaching 1.221 infective bites/person/night (ib/p/n), An. arabiensis and An. coluzzii were the most implicated. The roles of An. funestus, An. pharoensis and An. paludis were minor. Plasmodium falciparum circumsporozoite protein rate in Anopheles rufipes varied from 0.6 to 5.7% with EIR values between 0.010 and 0.481 ib/p/n.The study highlights the epidemiological role of An. rufipes alongside the members of the An. gambiae complex, and several other sympatric species in human malaria transmission during the wet season in northern Cameroon. For the first time in Cameroon, An. rufipes has been shown to be an important local malaria vector, emphasising the need to review the malaria entomological profile across the country as pre-requisite to effective vector management strategies.


Antonio-Nkondjio C.,Laboratoire Of Recherche Sur Le Paludisme | Antonio-Nkondjio C.,Vector Group | Antonio-Nkondjio C.,University of Bamenda | Demanou M.,Service Of Virologie Center Pasteur Cameroun | And 4 more authors.
Parasites and Vectors | Year: 2013

Background: Insecticide treated materials remain the mainstay for malaria prevention. The current study reports on the entomological impact of cyfluthrin impregnated bed nets on malaria transmission in Mbandjock, a semi urban locality in southern Cameroon. Several findings pertaining to the recent distribution of LLINs across Cameroon are discussed. Methods. Malaria transmission and vector bionomics were monitored before and after impregnated net coverage. Bed nets were distributed in Mbandjock, whereas the locality of Nkoteng was free of bed nets during the entire study period. January to June 1997 represented the period before bed net coverage and September 1997 to September 1998 was the period after bed net coverage. Adult mosquitoes were collected by human landing catches. Mosquito genus and species were identified with morphological and molecular diagnostic tools. Anopheline salivary glands and ovaries were dissected to determine female infectious status and parity rates respectively. Results: A total of 6959 anophelines corresponding to 6029 in Mbandjock and 930 in Nkoteng were collected in the course of the study. Seven species were recorded in both cities: Anopheles coustani, An. funestus, An. gambiae sl, An. moucheti, An. ziemanni, An. nili and An. paludis. An. gambiae s.l. (>95% An. gambiae S molecular form) was the most abundant species representing 75.6% and 86.6% of the total anophelines caught in Mbandjock before and after bed net coverage respectively. The human biting rate (HBR) in Mbandjock decreased from 17 bites/human/night before bed net coverage to less than 4 bites/human/night during the first 7 months following impregnated bed net coverage. A significant decrease of mosquito parity rate was recorded when comparing the period before (52%) and after (46.5%) bed net distribution. The average infection rate of malaria vectors significantly decreased from 5.3% before to 1.8% after bed net coverage (p < 0.0001). The entomological inoculation rate in Mbandjock was reduced by 74% varying from 124.1 infected bites/human/year before bed net distribution, to 32.5 infected bites/human/year after bed net coverage. All entomological indexes were relatively stable in Nkoteng and no reduction of malaria transmission was recorded in this locality. Conclusion: The study confirms the effectiveness of cyfluthrin impregnated nets in reducing malaria transmission. Lessons from this study could be essential to draw guidelines for the management of the recent nationwide distribution of LLINs across Cameroon in 2011. © 2013 Antonio-Nkondjio et al.; licensee BioMed Central Ltd.


Bousema T.,London School of Hygiene and Tropical Medicine | Bousema T.,Radboud University Nijmegen | Churcher T.S.,Imperial College London | Morlais I.,Laboratoire Of Recherche Sur Le Paludisme | And 2 more authors.
Trends in Parasitology | Year: 2013

A recent meta-analysis of mosquito feeding assays to determine the Plasmodium falciparum transmission potential of naturally infected gametocyte carriers highlighted considerable variation in transmission efficiency between assay methodologies and between laboratories. This begs the question as to whether mosquito feeding assays should be used for the evaluation of transmission-reducing interventions in the field and whether these field-based mosquito assays are currently standardized sufficiently to enable accurate evaluations. Here, we address biological and methodological reasons for the observed variations, discuss whether these preclude the use of field-based mosquito feeding assays in field evaluations of transmission-blocking interventions, and propose how we can maximize the precision of estimates. Altogether, we underscore the significant advantages of field-based mosquito feeding assays in basic malaria research and field trials. © 2012 Elsevier Ltd.


Ndo C.,Laboratoire Of Recherche Sur Le Paludisme | Ndo C.,University of Yaounde I | Menze-Djantio B.,Laboratoire Of Recherche Sur Le Paludisme | Menze-Djantio B.,University of Yaounde I | And 2 more authors.
Parasites and Vectors | Year: 2011

Background: There is little information on the social perception of malaria and the use of prevention methods in Cameroon. This study was designed to assess knowledge, attitude and management of malaria in households living in the cities of Douala and Yaoundé. Results: Over 82% of people interviewed associated malaria transmission to mosquito bites. Methods used for malaria prevention were: environmental sanitation 1645 (76.1%), use of bed nets 1491 (69%), insecticide spray/coils 265 (12.3%) and netting of doors or windows 42 (1.9%). Bed net ownership was significantly high in Yaoundé (73.8%) (P < 0.0001), whereas the use of insecticide spray or coils was significantly important in Douala (16.3%) (P < 0.0001). Some of the problems experienced by families using ITN were the difficulty in finding chemicals for the retreatment of nets 702 (47%), insufficient financial means to buy new bed nets to replace old ones 366 (24.5%) or, to provide bed nets to everybody in the household 289 (19.4%) and the sensation of feeling excessive heat when sleeping under a bed net 74 (5%). The amount spent monthly by a household for vector control and malaria treatment was estimated at 2377 fcfa (3.6 euros) and 4562 fcfa (6.95 euros) respectively. These amounts were not significantly different between households of Douala and Yaoundé. Concerning management of malaria cases, 18.6% of people declare going to the hospital when suffering from malaria. The majority of people (81.4%) do self medication - they either buy drugs from the pharmacists, street sellers or they use plants to cure malaria. Conclusion: The study revealed a high awareness of populations on malaria and ITNs. However some attitudes hindering the use of ITN or related to the management of clinical cases need further attention. © 2011 Ndo et al; licensee BioMed Central Ltd.

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