Secondary Malaria Vectors of Sub-Saharan Africa: Threat to Malaria Elimination on the Continent?

Secondary vectors of malaria include those anopheline species that are known to play minor part in malaria transmission. Primary vectors of malaria in Africa are Anopheles gambiae s.s, Anopheles coluzzii, Anopheles arabiensis, Anopheles funestus, Anopheles moucheti and Anopheles nili, while Anopheles rivolorum, Anopheles pharoensis, Anopheles ziemanni, among others are secondary vectors. They are recognized for their importance in malaria transmission, as they may help to augment or extend the malaria transmission period and potentially sustain malaria transmission after the main indoor resting and indoor biting vectors have been reduced by vector control measures such as indoor residual spraying or Long-lasting insecticidal nets (LLINs). Thus, the terminology “secondary” versus “primary” vector is fluid and forged by ecological conditions and malaria control strategies. Most secondary vectors are outdoor resting and outdoor biting are thus, not taken care of in the current control methods. High use of insecticides for vector control in Africa, climate change, unprecedented land use changes in Africa are some of the factors that could influence the conversion of secondary vectors to become main vectors in Africa. This chapter examines the role of secondary vectors in malaria transmission and the possibility of them becoming main vectors in future

Aedes aegypti vector competence studies: A review.

Abstract Aedes aegypti is the primary transmitter of the four viruses that have had the greatest impact on human health, the viruses causing yellow fever, dengue fever, chikungunya, and Zika fever. Because this mosquito is easy to rear in the laboratory and these viruses grow in laboratory tissue culture cells, many studies have been performed testing the relative competence of different populations of the mosquito to transmit many different strains of viruses. We review here this large literature including studies on the effect of the mosquito microbiota on competence. Because of the heterogeneity of both mosquito populations and virus strains used, as well as methods measuring potential to transmit, it is very difficult to perform detailed meta-analysis of the studies. However, a few conclusions can be drawn: (1) almost no population of Ae. aegypti is 100% naturally refractory to virus infection. Complete susceptibility to infection has been observed for Zika (ZIKV), dengue (DENV) and chikungunya (CHIKV), but not yellow fever viruses (YFV); (2) the dose of virus used is directly correlated to the rate of infection; (3) Brazilian populations of mosquito are particularly susceptible to DENV-2 infections; (4) the Asian lineage of ZIKV is less infective to Ae. aegypti populations from the American continent than is the African ZIKV lineage; (5) virus adaptation to different species of mosquitoes has been demonstrated with CHIKV; (6) co-infection with more than one virus sometimes causes displacement while in other cases has little effect; (7) the microbiota in the mosquito also has important effects on level of susceptibility to arboviral infection; (8) resistance to virus infection due to the microbiota may be direct (e.g., bacteria producing antiviral proteins) or indirect in activating the mosquito host innate immune system; (9) non-pathogenic insect specific viruses (ISVs) are also common in mosquitoes including genome insertions. These too have been shown to have an impact on the susceptibility of mosquitoes to pathogenic viruses. One clear conclusion is that it would be a great advance in this type of research to implement standardized procedures in order to obtain comparable and reproducible results

Genetic structure of Plasmodium vivax and Plasmodium falciparum in the Bannu district of Pakistan

<p>Abstract</p> <p>Background</p> <p><it>Plasmodium vivax </it>and <it>Plasmodium falciparum </it>are the major causative agents of malaria. While knowledge of the genetic structure of malaria parasites is useful for understanding the evolution of parasite virulence, designing anti-malarial vaccines and assessing the impact of malaria control measures, there is a paucity of information on genetic diversity of these two malaria parasites in Pakistan. This study sought to shed some light on the genetic structure of <it>P. vivax </it>and <it>P. falciparum </it>in this understudied region.</p> <p>Methods</p> <p>The genetic diversities of <it>P. vivax </it>and <it>P. falciparum </it>populations from the densely populated, malaria-endemic Bannu district of Pakistan were evaluated by analysis of their merozoite surface protein (<it>msp</it>) genes by PCR-RFLP. Specifically, the <it>Pvmsp-3α </it>and <it>Pvmsp-3β </it>genes of <it>P. vivax </it>and the <it>Pfmsp-1 </it>and <it>Pfmsp-2 </it>genes of <it>P. falciparum </it>were analysed.</p> <p>Results</p> <p>In <it>P. vivax</it>, genotyping of <it>Pvmsp-3α </it>and <it>Pvmsp-3β </it>genes showed a high level of diversity at these loci. Four distinct allele groups: A (1.9 kb), B (1.5 kb), C (1.2 kb), and D (0.3 kb) were detected for <it>Pvmsp</it>-<it>3α</it>, type A being the most prevalent (82%). Conversely, amplification of the <it>P. vivax msp</it>-<it>3β </it>locus produced two allele groups: A (1.7-2.2 kb, 62%) and B (1.4-1.5 kb, 33%), with 5% mixed-strain infections. Restriction analysis of <it>Pvmsp-3α </it>and <it>Pvmsp-3β </it>yielded 12 and 8 distinct alleles, respectively, with a combined mixed genotype prevalence of 20%. In <it>P. falciparum</it>, all three known genotypes of <it>Pfmsp-1 </it>and two of <it>Pfmsp-2 </it>were observed, with MAD20 occurring in 67% and 3D7/IC in 65% of the isolates, respectively. Overall, 24% <it>P. falciparum </it>samples exhibited mixed-strain infections.</p> <p>Conclusion</p> <p>These results indicate that both <it>P. vivax </it>and <it>P. falciparum </it>populations in Pakistan are highly diverse.</p

Microsatellite polymorphism in tsetse flies (Diptera: Glossinidae).

In sub-Saharan Africa, tsetse flies are the vectors of trypanosomes, the causative agents of sleeping sickness in humans and nagana in animals. Certain wild populations of the palpalis group exhibit intraspecific variation and are suspect of manifest differences in vectorial capacity. The current study reports the identification of 13 polymorphic microsatellite loci from Glossina palpalis palpalis Robinean-Desvoidy. The majority of these markers amplify corresponding loci from the related species C. p. gambiensis Vanderplank, G. f. fuscipes Newstead, and G. tachinoides Westwood. Only seven of 13 loci were amplified from G. austeni Newstead. Genetic variability was estimated in one field population of G. p. gambiensis. These results confirmed that microsatellite markers may be used to examine the subpopulation structure of tsetse flies

QTL mapping of genome regions controlling temephos resistance in larvae of the mosquito aedes aegypti

Introduction: The mosquito Aedes aegypti is the principal vector of dengue and yellow fever flaviviruses. Temephos is an organophosphate insecticide used globally to suppress Ae. aegypti larval populations but resistance has evolved in many locations. Methodology/Principal Findings: Quantitative Trait Loci (QTL) controlling temephos survival in Ae. aegypti larvae were mapped in a pair of F3 advanced intercross lines arising from temephos resistant parents from Solidaridad, México and temephos susceptible parents from Iquitos, Peru. Two sets of 200 F3 larvae were exposed to a discriminating dose of temephos and then dead larvae were collected and preserved for DNA isolation every two hours up to 16 hours. Larvae surviving longer than 16 hours were considered resistant. For QTL mapping, single nucleotide polymorphisms (SNPs) were identified at 23 single copy genes and 26 microsatellite loci of known physical positions in the Ae. aegypti genome. In both reciprocal crosses, Multiple Interval Mapping identified eleven QTL associated with time until death. In the Solidaridad6Iquitos (SLD6Iq) cross twelve were associated with survival but in the reciprocal IqxSLD cross, only six QTL were survival associated. Polymorphisms at acetylcholine esterase (AchE) loci 1 and 2 were not associated with either resistance phenotype suggesting that target site insensitivity is not an organophosphate resistance mechanism in this region of México. Conclusions/Significance: Temephos resistance is under the control of many metabolic genes of small effect and dispersed throughout the Ae. aegypti genome

Relevant genetic differentiation among Brazilian populations of Anastrepha fraterculus (Diptera, Tephritidae)

We used a population genetic approach to detect the presence of genetic diversity among six populations of A. fraterculus across Brazil. To this aim, we used Simple Sequence Repeat (SSR) markers, which may capture the presence of differentiative processes across the genome in distinct populations. Spatial analyses of molecular variance were used to identify groups of populations that are both genetically and geographically homogeneous while also being maximally differentiated from each other. The spatial analysis of genetic diversity indicates that the levels of diversity among the six populations vary significantly on an eco-geographical basis. Particularly, altitude seems to represent a differentiating adaptation, as the main genetic differentiation is detected between the two populations present at higher altitudes and the other four populations at sea level. The data, together with the outcomes from different cluster analyses, identify a genetic diversity pattern that overlaps with the distribution of the known morphotypes in the Brazilian area.Fil: Manni, Mosè. Università degli Studi di Pavia; ItaliaFil: Lima, Kátia Manuela. Universidade Estadual de Santa Cruz; BrasilFil: Rosalba Guglielmino, Carmela. Università degli Studi di Pavia; ItaliaFil: Lanzavecchia, Silvia Beatriz. Instituto Nacional de Tecnología Agropecuaria. Centro Nacional de Investigaciones Agropecuarias. Centro de Investigación de Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Juri, Marianela Lucia. Instituto Nacional de Tecnología Agropecuaria. Centro Nacional de Investigaciones Agropecuarias. Centro de Investigación de Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vera, Maria Teresa. Universidad Nacional de Tucumán. Facultad de Agronomía y Zootecnia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cladera, Jorge. Instituto Nacional de Tecnología Agropecuaria. Centro Nacional de Investigaciones Agropecuarias. Centro de Investigación de Ciencias Veterinarias y Agronómicas. Instituto de Genética; ArgentinaFil: Scolari, Francesca. Università degli Studi di Pavia; ItaliaFil: Gomulski, Ludvik. Università degli Studi di Pavia; ItaliaFil: Bonizzoni, Mariangela. Università degli Studi di Pavia; ItaliaFil: Gasperi, Giuliano. Università degli Studi di Pavia; ItaliaFil: Gomes Silva, Janisete. Universidade Estadual de Santa Cruz; BrasilFil: Malacrida, Anna Rodolfa. Università degli Studi di Pavia; Itali

A genotyping array for the globally invasive vector mosquito, Aedes albopictus

Background: Although whole-genome sequencing (WGS) is the preferred genotyping method for most genomic analyses, limitations are often experienced when studying genomes characterized by a high percentage of repetitive elements, high linkage, and recombination deserts. The Asian tiger mosquito (Aedes albopictus), for example, has a genome comprising up to 72% repetitive elements, and therefore we set out to develop a single-nucleotide polymorphism (SNP) chip to be more cost-effective. Aedes albopictus is an invasive species originating from Southeast Asia that has recently spread around the world and is a vector for many human diseases. Developing an accessible genotyping platform is essential in advancing biological control methods and understanding the population dynamics of this pest species, with significant implications for public health. Methods: We designed a SNP chip for Ae. albopictus (Aealbo chip) based on approximately 2.7 million SNPs identified using WGS data from 819 worldwide samples. We validated the chip using laboratory single-pair crosses, comparing technical replicates, and comparing genotypes of samples genotyped by WGS and the SNP chip. We then used the chip for a population genomic analysis of 237 samples from 28 sites in the native range to evaluate its usefulness in describing patterns of genomic variation and tracing the origins of invasions. Results: Probes on the Aealbo chip targeted 175,396 SNPs in coding and non-coding regions across all three chromosomes, with a density of 102 SNPs per 1 Mb window, and at least one SNP in each of the 17,461 protein-coding genes. Overall, 70% of the probes captured the genetic variation. Segregation analysis found that 98% of the SNPs followed expectations of single-copy Mendelian genes. Comparisons with WGS indicated that sites with genotype disagreements were mostly heterozygotes at loci with WGS read depth \u3c 20, while there was near complete agreement with WGS read depths \u3e 20, indicating that the chip more accurately detects heterozygotes than low-coverage WGS. Sample sizes did not affect the accuracy of the SNP chip genotype calls. Ancestry analyses identified four to five genetic clusters in the native range with various levels of admixture. Conclusions: The Aealbo chip is highly accurate, is concordant with genotypes from WGS with high sequence coverage, and may be more accurate than low-coverage WGS. Graphical Abstract: (Figure presented.) © The Author(s) 2024

A systematic review and meta-analysis of e-Mental Health interventions to treat symptoms of post-traumatic stress

Quality control of RNA-seq data: Box Plot of transcript quantification levels. The distributions of FPKM scores across samples are visualized. (PDF 130 kb

Improved reference genome of the arboviral vector Aedes albopictus

Background: The Asian tiger mosquito Aedes albopictus is globally expanding and has become the main vector for human arboviruses in Europe. With limited antiviral drugs and vaccines available, vector control is the primary approach to prevent mosquito-borne diseases. A reliable and accurate DNA sequence of the Ae. albopictus genome is essential to develop new approaches that involve genetic manipulation of mosquitoes. Results: We use long-read sequencing methods and modern scaffolding techniques (PacBio, 10X, and Hi-C) to produce AalbF2, a dramatically improved assembly of the Ae. albopictus genome. AalbF2 reveals widespread viral insertions, novel microRNAs and piRNA clusters, the sex-determining locus, and new immunity genes, and enables genome-wide studies of geographically diverse Ae. albopictus populations and analyses of the developmental and stage-dependent network of expression data. Additionally, we build the first physical map for this species with 75% of the assembled genome anchored to the chromosomes. Conclusion: The AalbF2 genome assembly represents the most up-to-date collective knowledge of the Ae. albopictus genome. These resources represent a foundation to improve understanding of the adaptation potential and the epidemiological relevance of this species and foster the development of innovative control measures