Molecular Characterization and Genotype Distribution of Thioester-containing Protein 1 Gene, A Key Regulator of Malaria Transmission in An. Gambiae Mosquitoes in Western Kenya

Abstract BackgroundEvolutionary pressures lead to the selection of efficient malaria vectors either resistant or susceptible to Plasmodiumparasites.These forcesmay elevate the introduction of new species genotypes that adapt to new breeding habitats which could have serious implications on malaria transmission.Thioester-containing protein 1 (TEP1) of Anopheles gambiaeplays an important role in innate immune defenses against parasites. This study aims to characterize the distribution pattern of TEP1 polymorphisms determining vector competence and subsequently malaria transmission in western Kenya. MethodsAnopheles gambiaeadult and larvae were collected using pyrethrum spray catches (PSC) and plastic dippers respectivelyfrom Homa Bay, Kakamega, Bungoma, and Kisumu countiesbetween 2017 and 2020.Collected adults and larvae reared to the adult stage were morphologically identified and then identified to sibling species by PCR.TEP1 alleles were determined using restriction fragment length polymorphisms-polymerase chain reaction (RFLP-PCR) and to validate the TEP1 genotyping results, a representative sample of alleles was sequenced.ResultsTwo TEP1 alleles (TEP1*S1 and TEP1*R2)and three corresponding genotypes (*S1/S1, *R2/S1, and *R2/R2)were identified. TEP1*S1 and TEP1*R2 with their corresponding genotypes, homozygous *S1/S1 and heterozygous *R2/S1 were widely distributed across all sites with allele frequencies of approximately 80% and 20%, respectively bothin An. gambiaeand An. arabiensis. There was no significant difference detected among the population and between the two mosquito species in TEP1 allele frequency and genotype frequency. The overall low levels in population structure (FST= 0.019) across all sites corresponded to an effective migration index (Nm= 12.571) and lowNei’s genetic distance values (<0.500) among the subpopulation.The comparative fixation index values revealed minimal genetic differentiation between speciesand high levels of gene flow among populations.ConclusionThere is a low genetic diversity and population structure in western Kenya. TEP1* R2 and TEP1*S1 were the most common alleles in both species which may have been maintained through generations in time, However, the TEP1*R2 allele was in low frequencies and may be used to estimatemalaria prevalence. Continued surveillance of the distribution of TEP1 is essential for monitoring the population dynamics of local vectors and their implications on malaria transmission and hence designing targeted vector interventions.

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Unravelling population structure heterogeneity within the genome of the malaria vector Anopheles gambiae

BMC Genomics ◽

10.1186/s12864-021-07722-y ◽

2021 ◽

Vol 22 (1) ◽

Author(s):

Melina Campos ◽

Luisa D. P. Rona ◽

Katie Willis ◽

George K. Christophides ◽

Robert M. MacCallum

Keyword(s):

Population Structure ◽

Anopheles Gambiae ◽

Malaria Vector ◽

Mosquito Species ◽

Gene Clusters ◽

Selective Sweeps ◽

Structure Heterogeneity ◽

Genomic Studies ◽

Time Required ◽

Genomic Regions

Abstract Background Whole genome re-sequencing provides powerful data for population genomic studies, allowing robust inferences of population structure, gene flow and evolutionary history. For the major malaria vector in Africa, Anopheles gambiae, other genetic aspects such as selection and adaptation are also important. In the present study, we explore population genetic variation from genome-wide sequencing of 765 An. gambiae and An. coluzzii specimens collected from across Africa. We used t-SNE, a recently popularized dimensionality reduction method, to create a 2D-map of An. gambiae and An. coluzzii genes that reflect their population structure similarities. Results The map allows intuitive navigation among genes distributed throughout the so-called “mainland” and numerous surrounding “island-like” gene clusters. These gene clusters of various sizes correspond predominantly to low recombination genomic regions such as inversions and centromeres, and also to recent selective sweeps. Because this mosquito species complex has been studied extensively, we were able to support our interpretations with previously published findings. Several novel observations and hypotheses are also made, including selective sweeps and a multi-locus selection event in Guinea-Bissau, a known intense hybridization zone between An. gambiae and An. coluzzii. Conclusions Our results present a rich dataset that could be utilized in functional investigations aiming to shed light onto An. gambiae s.l genome evolution and eventual speciation. In addition, the methodology presented here can be used to further characterize other species not so well studied as An. gambiae, shortening the time required to progress from field sampling to the identification of genes and genomic regions under unique evolutionary processes.

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Spatial Distribution of Anopheles gambiae and Anopheles funestus and Malaria Transmission in Suba District, Western Kenya

International Journal of Tropical Insect Science ◽

10.1017/s1742758400023584 ◽

2003 ◽

Vol 23 (03) ◽

pp. 187-196 ◽

Cited By ~ 4

Author(s):

Josephat I. Shililu ◽

Charles M. Mbogo ◽

Clifford M. Mutero ◽

James T. Gunter ◽

Chris Swalm ◽

...

Keyword(s):

Spatial Distribution ◽

Anopheles Gambiae ◽

Malaria Transmission ◽

Anopheles Funestus ◽

Western Kenya

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Plasmodium evasion of mosquito immunity and global malaria transmission: The lock-and-key theory

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1520426112 ◽

2015 ◽

Vol 112 (49) ◽

pp. 15178-15183 ◽

Cited By ~ 62

Author(s):

Alvaro Molina-Cruz ◽

Gaspar E. Canepa ◽

Nitin Kamath ◽

Noelle V. Pavlovic ◽

Jianbing Mu ◽

...

Keyword(s):

Immune System ◽

Malaria Transmission ◽

Immune Evasion ◽

Mosquito Species ◽

Haplotype Diversity ◽

Malaria Vectors ◽

Selective Force ◽

Genetic Traits ◽

Geographic Population

Plasmodium falciparum malaria originated in Africa and became global as humans migrated to other continents. During this journey, parasites encountered new mosquito species, some of them evolutionarily distant from African vectors. We have previously shown that the Pfs47 protein allows the parasite to evade the mosquito immune system of Anopheles gambiae mosquitoes. Here, we investigated the role of Pfs47-mediated immune evasion in the adaptation of P. falciparum to evolutionarily distant mosquito species. We found that P. falciparum isolates from Africa, Asia, or the Americas have low compatibility to malaria vectors from a different continent, an effect that is mediated by the mosquito immune system. We identified 42 different haplotypes of Pfs47 that have a strong geographic population structure and much lower haplotype diversity outside Africa. Replacement of the Pfs47 haplotypes in a P. falciparum isolate is sufficient to make it compatible to a different mosquito species. Those parasites that express a Pfs47 haplotype compatible with a given vector evade antiplasmodial immunity and survive. We propose that Pfs47-mediated immune evasion has been critical for the globalization of P. falciparum malaria as parasites adapted to new vector species. Our findings predict that this ongoing selective force by the mosquito immune system could influence the dispersal of Plasmodium genetic traits and point to Pfs47 as a potential target to block malaria transmission. A new model, the “lock-and-key theory” of P. falciparum globalization, is proposed, and its implications are discussed.

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Pollutants and insecticides drive local adaptation in African malaria mosquitoes

10.1101/067660 ◽

2016 ◽

Cited By ~ 1

Author(s):

Colince Kamdem ◽

Caroline Fouet ◽

Stephanie Gamez ◽

Bradley J. White

Keyword(s):

Anopheles Gambiae ◽

Local Adaptation ◽

Mosquito Species ◽

Sensu Stricto ◽

Detoxification Enzymes ◽

Malaria Vectors ◽

Breeding Sites ◽

Reduced Representation ◽

Malaria Epidemiology ◽

Rural And Urban

ABSTRACTThe Anopheles gambiae complex contains a number of highly anthropophilic mosquito species that have acquired exceptional ability to thrive in complex human habitats. Thus, examining the evolutionary history of this Afrotropical mosquito may yield vital information on the selective processes that occurred during the adaptation to human-dominated environments. We performed reduced representation sequencing on 941 mosquitoes of the Anopheles gambiae complex collected across four ecogeographic zones in Cameroon. We find evidence for genetic and geographic subdivision within An. coluzzii and An. gambiae sensu stricto – the two most significant malaria vectors in the region. Importantly, in both species, rural and urban populations are genetically differentiated. Genome scans reveal pervasive signatures of selection centered on genes involved in xenobiotic resistance. Notably, a selective sweep containing detoxification enzymes is prominent in urban mosquitoes that exploit polluted breeding sites. Overall, our study suggests that recent anthropogenic environmental modifications and widespread use of insecticides are driving population differentiation and local adaptation in vectors with potentially significant consequences for malaria epidemiology.

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Anopheles gambiae and Anopheles arabiensis population densities and infectivity in Kopere village, Western Kenya

The Journal of Infection in Developing Countries ◽

10.3855/jidc.1979 ◽

2012 ◽

Vol 6 (08) ◽

pp. 637-643 ◽

Cited By ~ 5

Author(s):

Andrew Ambogo Obala ◽

Helen L Kutima ◽

Henry D.N. Nyamogoba ◽

Anne W Mwangi ◽

Chrispinus J Simiyu ◽

...

Keyword(s):

Anopheles Gambiae ◽

Malaria Vector ◽

Anopheles Arabiensis ◽

Mosquito Species ◽

Sensu Stricto ◽

Malaria Vector Control ◽

Insecticide Treated Nets ◽

Western Kenya ◽

Endemic Malaria ◽

Vector Mosquito

Introduction: This study was conducted in a sugar belt region of western Kenya interfacing epidemic and endemic malaria transmission. We investigated Anopheles gambiae sensu stricto (ss) and Anopheles arabiensis species compositions and densities, human host choice, and infectivity. Methodology: Mosquitoes were captured using pyrethrum spray catch technique and first identified based on morphology; species were confirmed by PCR. Blood meal preference and sporozoite rates were determined by ELISA. Parity rates and entomological inoculation rates (EIR) were determined. Seasonal densities were compared against environmental temperatures, relative humidity and rainfall. Results: In total 2,426 An. gambiae were collected. Out of 1,687 female blood-fed mosquitoes, 272 were randomly selected for entomological tests. An. gambiae ss and An. arabiensis comprised 75% (205/272) and 25% (68/272) of the selection, respectively. An. gambiae ss had higher preference for human blood (97%; n=263/272) compared with An. arabiensis, which mostly fed on bovines (88%; n=239/272). The sporozoite and parity rates were 6% (16/272) and 66% (179/272) for An. gambiae ss and 2% (4/272) and 53% (144/272) for An. arabiensis respectively, while EIR was 0.78 infective bites/person/night. Climate (ANOVA; F=14.2; DF=23) and temperature alone (r=0.626; t=3.75; p=0.001) were significantly correlated with vector densities. Conclusion: An. gambiae ss are the most efficient malaria vector mosquito species in Kopere village. Because An. gambiae ss largely rests and feeds indoors, use of indoor residual spray and insecticide-treated nets is likely the most suitable approach to malaria vector control in Kopere village and other parts of Kenya where this species is abundant.

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Effect of bendiocarb based (Ficam® 80% WP) Indoor Residual Spraying on feeding patterns from malaria vectors in Burkina Faso, West Africa.

10.21203/rs.3.rs-20419/v1 ◽

2020 ◽

Author(s):

Sawdetuo Aristide HIEN ◽

Dieudonné Diloma Soma ◽

Simon Pengwende Sawadogo ◽

Serge Bèwadéyir Poda ◽

Moussa Namountougou ◽

...

Keyword(s):

Burkina Faso ◽

Anopheles Gambiae ◽

Malaria Transmission ◽

Malaria Vector ◽

Indoor Residual Spraying ◽

Transmission Risk ◽

Malaria Vectors ◽

Anopheles Coluzzii ◽

Transmission Season ◽

Density Methods

Abstract Background The fight against vector is essential in malaria prevention strategies in several endemic countries in Africa. In Burkina Faso, malaria transmission is seasonal in most parts of country, so a single round of spraying should provide effective protection against malaria, provided the insecticide remains effective over the entire malaria transmission season. The outcomes of indoor residual spraying towards curtailing malaria transmission are firstly to decrease the life span of vector mosquitoes and also to reduce the malaria vectors density. Methods CDC light trap and early morning collections by pyrethrum spray catches were performed monthly to determine the change in malaria vector indices in sprayed (Diebougou) and unsprayed sites (Dano). The female’s malaria vectors collected by both methods were used to determine their blood feeding, biting and sporozoites rate and malaria transmission risk estimated by entomological inoculation rate. Results Anopheles gambiae complex composed to Anopheles gambiae, Anopheles coluzzii and Anopheles arabiensis were present throughout the transmission season, but An. gambiae was the predominant species collected (P =0.0005), comprising 88% of the total collected and the most infected species. Malaria vectors densities were significantly lower in sprayed villages (n=4,303) compared with unsprayed villages (n=12,569) during post-spraying period (P = 0.0012). In addition, mean human biting rate of An. gambiae sl and An . funestus ss were significantly lower in sprayed areas compared to unsprayed areas (P<0.05). Overall, malaria vector transmission risk was significant lower in villages which received IRS (P=0.0001) whatever the malaria vectors species ( An. gambiae sl and An. funestus ss). Conclusions The results showed that in the sprayed area (Diebougou), vector densities, human biting rates and malaria transmission risks were very lower than unsprayed areas (Dano). The findings also showed a change in vector behavior especially within An. funestus which became more zoophagic following IRS. The indoor residual spraying could be recommanded as control tool in areas where malaria transmission occured a given period of year.

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Malaria Transmission, Vector Diversity, and Insecticide Resistance at a Peri-Urban Site in the Forest Zone of Ghana

Frontiers in Tropical Diseases ◽

10.3389/fitd.2021.739771 ◽

2021 ◽

Vol 2 ◽

Author(s):

Yaw Akuamoah-Boateng ◽

Ruth C. Brenyah ◽

Sandra A. Kwarteng ◽

Patrick Obuam ◽

Isaac Owusu-Frimpong ◽

...

Keyword(s):

Insecticide Resistance ◽

Anopheles Gambiae ◽

Malaria Transmission ◽

Urban Setting ◽

World Health ◽

Malaria Vectors ◽

Urban Site ◽

Human Landing Catch ◽

Anopheles Coluzzii ◽

Anopheles Gambiae S.S

IntroductionRecent surge of Anopheles resistance to major classes of World Health Organization (WHO)-approved insecticides globally necessitates the need for information about local malaria vector populations. It is believed that insecticide efficacy loss may lead to operational failure of control interventions and an increase in malaria infection transmission. We investigated the susceptibility levels of malaria vectors to all classes of WHO-approved vector control insecticides and described the dynamics of malaria transmission in a peri-urban setting.MethodsFit 3–5-day-old adults that emerged from Anopheles larvae collected from several different sites in the study area were subjected to the WHO bioassay for detecting insecticide resistance. The knockdown resistance gene (kdr) mutations within the vector populations were detected using PCR. Entomological inoculation rates were determined using the human landing catch technique and Plasmodium falciparum circumsporozoite ELISA.ResultsThe malaria vectors from the study area were resistant to all classes of insecticides tested. Out of the 284 Anopheles complex specimen assayed for the resistance study, 265 (93.30%) were identified as Anopheles gambiae s.s. The kdr gene was detected in 90% of the Anopheles gambiae s.s. assayed. In an area where Anopheles coluzzii resistance to insecticides had never been reported, the kdr gene was detected in 78% of the Anopheles coluzzii sampled. The entomological inoculation rate (EIR) for the dry season was 1.44 ib/m/n, whereas the EIR for the rainy season was 2.69 ib/m/n.ConclusionsThis study provides information on the high parasite inoculation rate and insecticide resistance of malaria vectors in a peri-urban community, which is critical in the development of an insecticide resistance management program for the community.

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Molecular Identification of Native Wolbachia Pipientis in Anopheles Minimus in a Low-Malaria Transmission Area of Umphang Valley Along the Thailand-Myanmar Border

10.21203/rs.3.rs-34081/v1 ◽

2020 ◽

Author(s):

Nongnat Tongkrajang ◽

Pichet Ruenchit ◽

Chatchai Tananchai ◽

Theeraphap Chareonviriyaphap ◽

Kasem Kulkeaw

Keyword(s):

Malaria Transmission ◽

Dna Sequences ◽

Phylogenetic Trees ◽

Mosquito Species ◽

Malaria Vectors ◽

Molecular Evidence ◽

Wolbachia Pipientis ◽

Close Relationship ◽

Transmission Area ◽

Low Malaria Transmission

Abstract BackgroundWolbachia, obligate intracellular bacteria, infect the majority of arthropods, including many mosquito species of medical importance. Some Wolbachia strains interfere with the development of Plasmodium parasites in female Anopheles, a major vector of malaria. The use of Wolbachia as a means to block malaria transmission is an emerging vector control strategy in highly endemic areas. Hence, identification of native Wolbachia strains in areas where malaria transmission is low may uncover a particular Wolbachia strain capable of Plasmodium interference. This study aims to identify native Wolbachia strains in female Anopheles spp. that are predominant in a low-malaria transmission area in mainland Southeast Asia.MethodsFollowing a two-year survey of malaria vectors in Umphang Valley of Tak Province, Thailand, DNA extracts of female An. minimus, An. peditaeniatus, An. maculatus, and An. dirus were subjected to amplification of the conserved region of the 16S rRNA-encoding gene. The DNA sequences of the amplicons were phylogenetically compared with those of known Wolbachia strains.ResultsAmong four Anopheles spp., amplification was detected in only the DNA samples from An. minimus. The DNA sequencing of amplicons revealed 100% similarity to Wolbachia pipientis, confirming the specificity of amplification. The phylogenetic trees indicate a close relationship with Wolbachia strains in subgroup B.ConclusionTo the best of our knowledge, the data presented herein provide the first molecular evidence of a Wolbachia strain in An. minimus, hereinafter named wAnmi, in a low-malaria transmission area in the Umphang Valley of western Thailand. Further biological characterization is required to examine its potential for malaria transmission control in the field.

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Entomological Indicators of Malaria Transmission Prior to a Cluster Randomised Controlled Trial of a “Lethal House Lure” Intervention in Central Côte D’Ivoire

10.21203/rs.3.rs-1146656/v1 ◽

2021 ◽

Author(s):

Rosine Zlanneu Wolie ◽

Alphonsine A. Koffi ◽

Lesley Ayuk-Taylor ◽

Ludovic P. Ahoua Alou ◽

Eleanore D. Sternberg ◽

...

Keyword(s):

Anopheles Gambiae ◽

Malaria Transmission ◽

Cote D'ivoire ◽

Côte D’Ivoire ◽

Controlled Trial ◽

Anopheles Funestus ◽

Malaria Vectors ◽

Cote D’Ivoire ◽

Côte D'ivoire ◽

Indoor And Outdoor

Abstract Background: A study was conducted prior to implementing a cluster randomised controlled trial (CRT) of a lethal house lure strategy in central Côte d’Ivoire and aimed to provide baseline information on malaria vectors in 40 village clusters. Methods: Human landing catches (HLC) was performed between November-December 2016, capturing mosquitoes indoor and outdoor between 18.00-08.00. Mosquitoes were processed for entomological indicators of malaria transmission (human biting rates, parity rates, sporozoite infection rates and the entomological inoculation rates (EIR)). Species composition and allelic frequencies of Kdr-w and Ace-1R mutations were also investigated within the Anopheles gambiae complex. Results: Overall, 15,632 mosquitoes were captured. Anopheles gambiae s.l. and Anopheles funestus were the two malaria vectors found during the survey period, with predominance for Anopheles gambiae s.l. (66.2%) compared to Anopheles funestus (10.3%). The mean biting rate for An. gambiae s.l. was almost 5 times higher than that for An. funestus s.l.(19.8 bites per person per night for An. gambiae s. l. vs 4.3 bites per person per night for An. funestus s. l.) and this was evident indoor and outdoor. An. funestus was more competent to transmit malaria parasites in the study area, despite relatively lower number tested for sporozoite index (1.6% (1,373) for An. gambiae vs 4.7 % (722) for An. funestus s.l.). There was no significant difference between the proportion infected outdoor and indoor for An. gambiae s.l. (1.6% vs 1.5%; OR=1.11[0.65-1.9]; P=0.676), but for An. funestus, more mosquitoes were infected outdoor (6.4%) than indoor (3.5%) (OR=1.86 [1.07-3.23]; P=0.0249). The majority of both infected vectors with malaria parasites harboured P. falciparum (90.6% for An. gambiae s. l. and 97, 8% for An. funestus s. l.). The EIR for both vectors (0.43 infected bites per night) were similar and there were no significant differences for transmission occurring outdoor and indoor for both species. Of the An. gambiae s.l. analysed, only An. gambiae (14.1%) and An. coluzzii (85.9%) were found. The allelic frequencies of Kdr and Ace-1R were higher in An. gambiae (0.97 for Kdr and 0.19 for Ace-1R) than in An. coluzzii (0.86 for Kdr and 0.10 for Ace-1R) (P<0.001).Conclusion: Despite universal coverage of long-lasting insecticidal nets (LLINs) in the area, there was an abundance of malaria vectors in the study in area in central Côte d’Ivoire, specifically highly resistant An. gambiae s.l. as well as An. funestus s.l.. The malaria sporozoite rate was higher in An. funestus s.l than An. gambiae s.l.. but EIR rates in these two species were similarly high, both indoor and outdoor. Novel tools or strategies are urgently needed to further reduce malaria transmission in this area.

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