André Luis Costa-da-Silva

Genetic lineages in the yellow fever mosquito Aedes (Stegomyia) aegypti (Diptera: Culicidae) from Peru

The yellow fever mosquito Aedes aegypti was introduced in Peru in 1852 and was considered to be eradicated in 1958. In 2001, Ae. aegypti had been recorded in 15 out of 24 Peruvian Departments. Peru has great ecological differences between the east and west sides of Andes. Because of this, we consider that Ae. aegypti populations of both east and west sides can have a genetically distinct population structure. In this study we examined genetic variability and genealogical relationships among three Ae. aegypti Peruvian populations: Lima, Piura (west Andes), and Iquitos (east Andes) using a fragment of the ND4 gene of the mitochondrial genome. Three haplotypes were detected among 55 samples. Lima and Iquitos showed the same haplotype (Haplotype I), whereas Piura has two haplotypes (Haplotype II and III). Haplotype II is four mutational steps apart from Haplotype I, while Haplotype III is 13 mutational steps apart from Haplotype I in the network. The analysis of molecular variation showed that mostly of the detected genetic variation occurs at interpopulational level. The significant value Phi(st) suggests that Piura population is structured in relation to Lima and Iquitos populations and the gene flow of the ND4 is restricted in Piura when compared to Lima and Iquitos. Genetic relationship between haplotype I and haplotype II suggests introduction of the same mtDNA lineage into those localities. However the existence of a genetically distant haplotype III also suggests introduction of at least two Ae. aegypti lineages in Peru.

Aedes aegypti Control Strategies in Brazil: Incorporation of New Technologies to Overcome the Persistence of Dengue Epidemics

Dengue is considered to be the most important mosquito-borne viral disease in the world. The Aedes aegypti mosquito, its vector, is highly anthropophilic and is very well adapted to urban environments. Although several vaccine candidates are in advanced stages of development no licensed dengue vaccine is yet available. As a result, controlling the spread of dengue still requires that mosquitoes be targeted directly. We review the current methods of dengue vector control focusing on recent technical advances. We first examine the history of Brazil’s National Dengue Control Plan in effect since 2002, and we describe its establishment and operation. With the persistent recurrence of dengue epidemics, current strategies should be reassessed to bring to the forefront a discussion of the possible implementation of new technologies in Brazil’s mosquito control program.

São Paulo urban heat islands have a higher incidence of dengue than other urban areas

Urban heat islands are characterized by high land surface temperature, low humidity, and poor vegetation, and considered to favor the transmission of the mosquito-borne dengue fever that is transmitted by the Aedes aegypti mosquito. We analyzed the recorded dengue incidence in Sao Paulo city, Brazil, in 2010-2011, in terms of multiple environmental and socioeconomic variables. Geographical information systems, thermal remote sensing images, and census data were used to classify city areas according to land surface temperature, vegetation cover, population density, socioeconomic status, and housing standards. Of the 7415 dengue cases, a majority (93.1%) mapped to areas with land surface temperature >28°C. The dengue incidence rate (cases per 100,000 inhabitants) was low (3.2 cases) in high vegetation cover areas, but high (72.3 cases) in low vegetation cover areas where the land surface temperature was 29±2°C. Interestingly, a multiple cluster analysis phenogram showed more dengue cases clustered in areas of land surface temperature >32°C, than in areas characterized as low socioeconomic zones, high population density areas, or slum-like areas. In laboratory experiments, A. aegypti mosquito larval development, blood feeding, and oviposition associated positively with temperatures of 28-32°C, indicating these temperatures to be favorable for dengue transmission. Thus, among all the variables studied, dengue incidence was most affected by the temperature.

Two step male release strategy using transgenic mosquito lines to control transmission of vector-borne diseases.

Mosquitoes are responsible for the transmission of pathogens that cause devastating human diseases such as malaria and dengue. The current increase in mean global temperature and changing sea level interfere with precipitation frequency and some other climatic conditions which, in general, influence the rate of development of insects and etiologic agents causing acceleration as the temperature rises. The most common strategy employed to combat target mosquito species is the Integrated Vector Management (IVM), which comprises the use of multiple activities and various approaches to preventing the spread of a vector in infested areas. IVM programmes are becoming ineffective; and the global scenario is threatening, requiring new interventions for vector control and surveillance. Not surprisingly, there is a growing need to find alternative methods to combat the mosquito vectors. The possibility of using transgenic mosquitoes to fight against those diseases has been discussed over the last two decades and this use of transgenic lines to suppress populations or to replace them is still under investigation through field and laboratory trials. As an alternative, the available transgenic strategies could be improved by coupling suppression and substitution strategies. The idea is to first release a suppression line to significantly reduce the wild population, and once the first objective is reached a second release using a substitution line could be then performed. Examples of targeting this approach against vectors of malaria and dengue are discussed.

Expression and accumulation of the two-domain odorant-binding protein AaegOBP45 in the ovaries of blood-fed Aedes aegypti

BackgroundAedes aegypti mosquitoes are the main vectors of dengue viruses. Despite global efforts to reduce the prevalence of dengue using integrated vector management strategies, innovative alternatives are necessary to help prevent virus transmission. Detailed characterizations of Ae. aegypti genes and their products provide information about the biology of mosquitoes and may serve as foundations for the design of new vector control methods.FindingsWe studied the Ae. aegypti gene, AAEL010714, that encodes a two-domain odorant-binding protein, AaegOBP45. The predicted gene structure and sequence were validated, although single nucleotide polymorphisms were observed. Transcriptional and translational products accumulate in the ovaries of blood fed females and are not detected or are at low abundance in other tissues.ConclusionsWe validated the Ae. aegypti AAEL010714 gene sequence and characterized the expression profile of a two-domain OBP expressed in ovaries. We propose that AaegOBP45 function as a component of the mosquito eggshell.

Glytube: A Conical Tube and Parafilm M-Based Method as a Simplified Device to Artificially Blood-Feed the Dengue Vector Mosquito, Aedes aegypti

Aedes aegypti, the main vector of dengue virus, requires a blood meal to produce eggs. Although live animals are still the main blood source for laboratory colonies, many artificial feeders are available. These feeders are also the best method for experimental oral infection of Ae. aegypti with Dengue viruses. However, most of them are expensive or laborious to construct. Based on principle of Rutledge-type feeder, a conventional conical tube, glycerol and Parafilm-M were used to develop a simple in-house feeder device. The blood feeding efficiency of this apparatus was compared to a live blood source, mice, and no significant differences (p = 0.1189) were observed between artificial-fed (51.3% of engorgement) and mice-fed groups (40.6%). Thus, an easy to assemble and cost-effective artificial feeder, designated “Glytube” was developed in this report. This simple and efficient feeding device can be built with common laboratory materials for research on Ae. aegypti.

Laboratory strains of Aedes aegypti are competent to Brazilian Zika virus

The Zika virus outbreaks are unprecedented human threat in relation to congenital malformations and neurological/autoimmune complications. Since this virus has high potential to spread in regions presenting the vectors, improvement in mosquito control is a top priority. Thus, Aedes aegypti laboratory strains will be fundamental to support studies in different research fields implicated on Zika-mosquito interactions which are the basis for the development of innovative control methods. In this sense, our aim was to determine the main infection aspects of a Brazilian Zika strain in reference Aedes aegypti laboratory mosquitoes. We orally exposed Rockefeller, Higgs and Rexville mosquitoes to the Brazilian ZIKV (ZIKVBR) and qRT-PCR was applied to determine the infection, dissemination and detection rates of ZIKV in the collected saliva as well as viral levels in mosquito tissues. The three strains sustain the virus development but Higgs showed significantly lower viral loads in bodies at 14 days post-infection (dpi) and the lowest prevalences in bodies and heads. The Rockefeller strain was the most susceptible at 7 dpi but similar dissemination rates were observed at 14 dpi. Although variations exist, the ZIKVBR RNA shows detectable levels in saliva of the three strains at 14 dpi but is only detected in Rockefeller at 7 dpi. Moreover, saliva samples from the three strains were confirmed to be infectious when intrathoracically injected into mosquitoes. The ZIKVBR kinetics was monitored in Rockefeller mosquitoes and virus could be identified in the heads at 4 dpi but was more consistently detected late in infection. Our study presents the first evaluation on how Brazilian Zika virus behaves in reference Aedes aegypti strains and shed light on how the infection evolves over time. Vector competence and hallmarks of the ZIKVBR development were revealed in laboratory mosquitoes, providing additional information to accelerate studies focused on ZIKV-mosquito interactions.

First report of naturally infected Aedes aegypti with chikungunya virus genotype ECSA in the Americas

Background The worldwide expansion of new emergent arboviruses such as Chikungunya and Zika reinforces the importance in understanding the role of mosquito species in spreading these pathogens in affected regions. This knowledge is essential for developing effective programs based on species specificity to avoid the establishment of endemic transmission cycles sustained by the identified local vectors. Although the first autochthonous transmission of Chikungunya virus was described in 2014 in the north of Brazil, the main outbreaks were reported in 2015 and 2016 in the northeast of Brazil. Methodology/Principal findings During 5 days of February 2016, we collected mosquitoes in homes of 6 neighborhoods of Aracaju city, the capital of Sergipe state. Four mosquito species were identified but Culex quinquefasciatus and Aedes aegypti were the most abundant. Field-caught mosquitoes were tested for Chikungunya (CHIKV), Zika (ZIKV) and Dengue viruses (DENV) by qRT-PCR and one CHIKV-infected Ae. aegypti female was detected. The complete sequence of CHIKV genome was obtained from this sample and phylogenetic analysis revealed that this isolate belongs to the East-Central-South-African (ECSA) genotype. Conclusions Our study describes the first identification of a naturally CHIKV-infected Ae. aegypti in Brazil and the first report of a CHIKV from ECSA genotype identified in this species in the Americas. These findings support the notion of Ae. aegypti being a vector involved in CHIKV outbreaks in northeast of Brazil.

Antiplasmodial activity study of angiotensin II via Ala scan analogs

Angiotensin II (AII) as well as analog peptides shows antimalarial activity against Plasmodium gallinaceum and Plasmodium falciparum, but the exact mechanism of action is still unknown. This work presents the solid‐phase synthesis and characterization of eight peptides corresponding to the alanine scanning series of AII plus the amide‐capped derivative and the evaluation of the antiplasmodial activity of these peptides against mature P. gallinaceum sporozoites. The Ala screening data indicates that the replacement of either the Ile5 or the His6 residues causes minor effects on the in vitro antiplasmodial activity compared with AII, i.e. AII (88%), [Ala6]‐AII (79%), and [Ala5]‐AII (75%). Analogs [Ala3]‐AII, [Ala1]‐AII, and AII‐NH2 showed antiplasmodial activity around 65%, whereas the activity of the [Ala8]‐AII, [Ala7]‐AII, [Ala4]‐AII, and [Ala2]‐AII analogs is lower than 45%. Circular dichroism data suggest that AII and the most active analogs adopt a β‐fold conformation in different solutions. All AII analogs, except [Ala4]‐AII and [Ala8]‐AII, show contractile responses and interact with the AT1 receptor, [Ala5]‐AII and [Ala6]‐AII. In conclusion, this approach is helpful to understand the contribution of each amino acid residue to the bioactivity of AII, opening new perspectives toward the design of new sporozoiticidal compounds. Copyright

Transcriptome sequencing and developmental regulation of gene expression in Anopheles aquasalis.

Background Anopheles aquasalis is a major malaria vector in coastal areas of South and Central America where it breeds preferentially in brackish water. This species is very susceptible to Plasmodium vivax and it has been already incriminated as responsible vector in malaria outbreaks. There has been no high-throughput investigation into the sequencing of An. aquasalis genes, transcripts and proteins despite its epidemiological relevance. Here we describe the sequencing, assembly and annotation of the An. aquasalis transcriptome. Methodology/Principal Findings A total of 419 thousand cDNA sequence reads, encompassing 164 million nucleotides, were assembled in 7544 contigs of ≥2 sequences, and 1999 singletons. The majority of the An. aquasalis transcripts encode proteins with their closest counterparts in another neotropical malaria vector, An. darlingi. Several analyses in different protein databases were used to annotate and predict the putative functions of the deduced An. aquasalis proteins. Larval and adult-specific transcripts were represented by 121 and 424 contig sequences, respectively. Fifty-one transcripts were only detected in blood-fed females. The data also reveal a list of transcripts up- or down-regulated in adult females after a blood meal. Transcripts associated with immunity, signaling networks and blood feeding and digestion are discussed. Conclusions/Significance This study represents the first large-scale effort to sequence the transcriptome of An. aquasalis. It provides valuable information that will facilitate studies on the biology of this species and may lead to novel strategies to reduce malaria transmission on the South American continent. The An. aquasalis transcriptome is accessible at http://exon.niaid.nih.gov/transcriptome/An_aquasalis/Anaquexcel.xlsx.