Zika virus detection, isolation and genome sequencing through Culicidae sampling during the epidemic in Vitória, Espírito Santo, Brazil

New artificial hematophagy system with attractive polymeric biofilm for maintenance of Culex quinquefasciatus (Diptera: Culicidae) in the laboratory

BACKGROUND

Maintaining mosquito colonies in the laboratory requires a blood supply so that females' oocytes can mature and oviposition can take place. In this study, a new artificial hematophagy system for colonization and maintenance of Culex quinquefasciatus in the laboratory was developed and tested.

METHODS

We developed an attractive polymeric biofilm including 25% L-lactic acid for use as a membrane in an artificial hematophagy system and compared the feeding rate of females with Parafilm-M®. We also evaluated the oviposition rate, larval survival and adult emergence of females fed through the attractive biofilm.

RESULTS

The average percentage of female Cx. quinquefasciatus fed through the attractive biofilm was 87%, while only 20% became engorged with Parafilm-M® (p < 0.0001). Feeding through the attractive biofilm developed in this study produced high levels of evaluated biological parameters; the percentage of egg laying by females that underwent artificial hematophagy through the biofilm was 90%, with an average of 158 eggs per raft. From these eggs, 97% of the larvae hatched, of which 95% reached the pupal stage. The adult emergence rate corresponded to 93% of pupae.

CONCLUSIONS

Insects fed with attractant through the biofilm system had a higher engorgement rate compared to those fed through Parafilm-M®. Our study is preliminary and suggests that polymeric biofilm has great potential for artificially feeding mosquitoes in the laboratory. Based on this research, new studies will be carried out with biofilm and different systems.

Genus Culex Linnaeus, 1758 (Diptera: Culicidae) as an Important Potential Arbovirus Vector in Brazil: An Integrative Review

The genus Culex has 817 species subdivided into 28 subgenera. It has a cosmopolitan distribution, being most abundant in countries with a tropical climate. Understanding the ecology and diversity of viruses circulating in the species of this genus is important for understanding their role as arbovirus vectors in Brazil. To conduct an integrative review to identify the importance of the Culex genus as arbovirus vectors in Brazil. A search was carried out for scientific papers in the PubMed, BVSalud, Patuá-IEC and International Catalogue of Arboviruses: including certain other viruses of vertebrates databases. 36 publications describing arbovirus detections in Culex mosquitoes collected in the field in Brazil were evaluated. A total of 42 arbovirus species were detected, as well as studies analyzing the vector competence of C. quinquefasciatus for the transmission of four different arboviruses. The study of the Culex genus and its role as a vector of arboviruses in Brazil is essential for understanding transmission cycles, with the main aim of reducing cases of human infection. Thus, entomovirological surveillance guides the implementation of actions to detect circulating arboviruses among vectors to anticipate measures aimed at preventing or reducing the risk of arbovirus outbreaks in the country.

Potential Nosocomial Infections by the Zika and Chikungunya Viruses in Public Health Facilities in the Metropolitan Area of Recife, Brazil

Since 2015, the Dengue, Zika, and Chikungunya viruses gained notoriety for their impact in public health in many parts of the globe, including Brazil. In Recife, the capital of Pernambuco State, the introduction of ZIKV impacted human population tremendously, owing to the increase in the number of neurological cases, such as the Guillain−Barré and congenital Zika disorders. Later, Recife was considered to be the epicenter for ZIKV epidemics in Brazil. For arboviral diseases, there are some risk factors, such as climate changes, low socioeconomic conditions, and the high densities of vectors populations, that favor the broad and rapid dispersion of these three viruses in the city. Therefore, continuous arbovirus surveillance provides an important tool for detecting these arboviruses and predicting new outbreaks. The purpose of the present study was to evaluate the circulation of DENV, ZIKV, and CHIKV by RT-qPCR in mosquitoes collected in health care units from the metropolitan area of Recife (MAR), during 2018. A total of 2321 female mosquitoes (357 pools) belonging to two species, Aedes aegypti and Culex quinquefasciatus, were collected from 18 different healthcare units, distributed in five cities from the MAR. Twenty-three pools were positive for ZIKV, out of which, seventeen were of C. quinquefasciatus and six were of A. aegypti. Positive pools were collected in 11/18 health care units screened, with Cq values ranging from 30.0 to 37.4 and viral loads varying from 1.88 × 107 to 2.14 × 109 RNA copies/mL. Nosocomial Aedes- and Culex-borne transmission of arbovirus are widely ignored by surveillance and vector control programs, even though healthcare-associated infections (HAI) are considered a serious threat to patient safety worldwide. Although the results presented here concern only the epidemiological scenario from 2018 in MAR, the potential of hospital-acquired transmission through mosquito bites is being overlooked by public health authorities. It is, therefore, of the ultimate importance to establish specific control programs for these locations.

Combining Immunoassays to Identify Zika Virus Infection in Dengue-Endemic Areas

Zika virus (ZIKV) is a mosquito-borne flavivirus that has recently emerged as a global health threat. The rise in ZIKV infections has driven an increased incidence of neonates born with microcephaly or other neurological malformations. Therefore, screening for ZIKV infection can considerably impact pregnant women, especially during the first trimester. The majority of ZIKV infections are mild or asymptomatic, and clinical diagnosis is inaccurate. Moreover, given the high level of cross-reactivity among flaviviruses, serological approaches to distinguish ZIKV from dengue virus (DENV) infections are complicated. We used the combination of DENV and ZIKV nonstructural protein 1 (NS1) IgG enzyme-linked immunosorbent assay (ELISA) and ZIKV NS1 blockade-of-binding (BOB) ELISA to test the convalescent sera of non-flavivirus, primary DENV, secondary DENV, and ZIKV infections. Our findings indicate that primary testing using a ZIKV NS1 IgG ELISA, the test of choice for large-scale ZIKV serosurvey studies, provided relatively high sensitivity. Moreover, the confirmation of positive ELISA results using the ZIKV NS1 BOB ELISA increased average specificity to 94.59% across serum samples. The combined use of two simple ELISAs for ZIKV serosurveys and the monitoring of ZIKV infection during pregnancy can elucidate the epidemiology, pathogenesis, and complications of ZIKV in DENV-endemic areas.

Tale of Viruses in Male Infertility

Male infertility is a condition where the males either become sterile or critically infertile. The World Health Organisation assessed that approximately 9% of the couple have fertility issues where the contribution of the male partner was estimated to be 50%. There are several factors that can amalgamate to give rise to male infertility. Among them are lifestyle factors, genetic factors and as well as several environmental factors. The causes of male infertility may be acquired, congenital or sometimes idiopathic. All these factors adversely affect the spermatogenesis process as well as they impart serious threats to male genital organs thus resulting in infertility. Viruses are submicroscopic pathogenic agents that rely on host for their replication and survival. They enter the host cell, hijack the host cell machinery to aid their own replication and exit the cell for a new round of infection. With the growing abundance of different types of viruses and the havoc they have stirred in the form of pandemics, it is very essential to decipher their route of entry inside the human body and understand their diverse functional roles in order to combat them. In this chapter, we will review how viruses invade the male genital system thus in turn leading to detrimental consequence on male fertility. We will discuss the tropism of various viruses in the male genital organs and explore their sexual transmissibility. This chapter will summarise the functional and mechanistic approaches employed by the viruses in inducing oxidative stress inside spermatozoa thus leading to male infertility. Moreover, we will also highlight the various antiviral therapies that have been studied so far in order to ameliorate viral infection in order to combat the harmful consequences leading to male infertility.

A review on structural genomics approach applied for drug discovery against three vector-borne viral diseases: Dengue, Chikungunya and Zika

Structural genomics involves the advent of three-dimensional structures of the genome encoded proteins through various techniques available. Numerous structural genomics research groups have been developed across the globe and they contribute enormously to the identification of three-dimensional structures of various proteins. In this review, we have discussed the applications of the structural genomics approach towards the discovery of potential lead-like molecules against the genomic drug targets of three vector-borne diseases, namely, Dengue, Chikungunya and Zika. Currently, all these three diseases are associated with the most important global public health problems and significant economic burden in tropical countries. Structural genomics has accelerated the identification of novel drug targets and inhibitors for the treatment of these diseases. We start with the current development status of the drug targets and antiviral drugs against these three diseases and conclude by describing challenges that need to be addressed to overcome the shortcomings in the process of drug discovery.

Arbovirus Surveillance in Field-Collected Mosquitoes From Pernambuco-Brazil, During the Triple Dengue, Zika and Chikungunya Outbreak of 2015-2017

The (re) emergence of arboviruses around the world is a public health concern once severe outbreaks are usually associated with these infections. The co-circulation of Dengue (DENV), Zika (ZIKV) and Chikungunya (CHIKV) viruses in the past few years has caused a unique epidemic situation in Brazil. The northeast region of the country was the most affected by clinical complications from such arboviruses’ infections, including neurological disorders caused by ZIKV. In this particular region, Aedes mosquitoes are the main vectors of DENV, ZIKV and CHIKV, with Culex quinquefasciatus also considered as a potential vector of ZIKV. Therefore, virological surveillance in mosquitoes contributes to understanding the epidemiological profile of these diseases. Here, we report the circulation of DENV, ZIKV and CHIKV in Aedes spp. and Cx. quinquefasciatus female mosquitoes collected in areas with a high arbovirus circulation in humans in the Metropolitan Region of Recife, Pernambuco, Brazil, during the triple-epidemics of 2015-17. All the field-caught mosquitoes were sent to the laboratory for arbovirus screening after RNA extraction and RT-PCR/RT-qPCR. A total of 6,227 females were evaluated and, as a result, DENV, ZIKV and CHIKV were identified in Ae. aegypti, Ae. taeniorhynchus and Cx. quinquefasciatus mosquito pools. In addition, DENV and ZIKV were isolated in C6/36 cells. In conclusion, it is important to highlight that arbovirus surveillance performed in mosquitoes from DENV-ZIKV-CHIKV hotspots areas can serve as an early-warning system to target vector control actions more efficiently in each studied area.

Human Polymorphonuclear Cells Support Zika Virus to Cross Endothelial Monolayer and Access Bloodstream

The rapid spread of new outbreaks of human infection caused by Zika virus (ZIKV) has raised many global concerns since 2016. Despite the increasing knowledge of this virus, data on the pathogenesis of ZIKV are still missing. In particular, it is still unknown how the virus crosses the endothelial monolayer and gets access to the bloodstream. In the present work, we used human umbilical vein endothelial cells (HUVECs) as a model to study ZIKV infection in vitro. We demonstrated that HUVECs are an optimal reservoir for viral replication, as they were able to sustain ZIKV infection up to two weeks, without showing a cytopathic effect. In order to evaluate the integrity of endothelial monolayer, immunofluorescence was performed on mock-infected or ZIKV-infected cells ± peripheral blood mononuclear cells (PBMCs) or polymorphonuclear cells (PMN), 48 h p.i., by using an anti-VE-Cadherin antibody, a major adherence protein that maintains the integrity of intercellular junctions. In addition to infection, we noted that the presence of some components of the immune system, such as PMNs, played an important role in altering the endothelial monolayer in cell junctions, suggesting that presence at the site of infection probably promotes the spread of ZIKV in vivo in the bloodstream.

Adaptations to haematophagy: Investigations on how male and female Culex quinquefasciatus (Diptera: Culicidae) deal with human complement activation after a blood meal

Culex quinquefasciatus is a mosquito species with an anthropophilic habit, often associated with areas with poor sanitation in tropical and urban regions. Adult males and females feed on sugars but only females feed on blood in natural conditions for egg maturation. During haematophagy, female C. quinquefasciatus transmit pathogens such as the West Nile virus, Oropouche virus, various encephalitis viruses, and Wuchereria bancrofti to human hosts. It has been observed in laboratory conditions that male C. quinquefasciatus may feed on blood during an artificial feed. Experiments were carried out to understand how males and females of this species deal with human complement activation. Our results showed that female C. quinquefasciatus, but not males, withstand the stress caused by the ingestion of normal human serum. It was observed that the salivary gland extracts from female mosquitoes were able to inhibit the classical and lectin pathways, whereas male salivary gland extracts only inhibited the lectin pathway. The male and female intestinal contents inhibited the classical and lectin pathways. Neither the salivary glands nor the intestinal contents from males and females showed inhibitory activity towards the alternative pathway. However, the guts of male and female C. quinquefasciatus captured factor H from the human serum, permitting C3b inactivation to its inactive form iC3b, and preventing the formation of the C3 convertase. The activity of the antioxidant enzyme catalase is similar in C. quinquefasciatus females and males. This article shows for the first time that males from a haematophagous arthropod species present human anti-complement activity in their salivary gland extracts and gut contents. The finding of an activity that helps to protect the damage caused by blood ingestion in sugar-feeding male mosquitoes suggests that this may be a pre-adaptation to blood-feeding.

Vector Competence of Aedes aegypti, Aedes albopictus and Culex quinquefasciatus from Brazil and New Caledonia for Three Zika Virus Lineages

Zika virus (ZIKV) has caused severe epidemics in South America beginning in 2015, following its spread through the Pacific. We comparatively assessed the vector competence of ten populations of Aedesaegypti and Ae. albopictus from Brazil and two of Ae.aegypti and one of Culex quinquefasciatus from New Caledonia to transmit three ZIKV isolates belonging to African, Asian and American lineages. Recently colonized mosquitoes from eight distinct sites from both countries were orally challenged with the same viral load (10⁷ TCID₅₀/mL) and examined after 7, 14 and 21 days. Cx. quinquefasciatus was refractory to infection with all virus strains. In contrast, although competence varied with geographical origin, Brazilian and New Caledonian Ae. aegypti could transmit the three ZIKV lineages, with a strong advantage for the African lineage (the only one reaching saliva one-week after challenge). Brazilian Ae. albopictus populations were less competent than Ae. aegypti populations. Ae. albopictus generally exhibited almost no transmission for Asian and American lineages, but was efficient in transmitting the African ZIKV. Viral surveillance and mosquito control measures must be strengthened to avoid the spread of new ZIKV lineages and minimize the transmission of viruses currently circulating.

Evaluation of Viral RNA Recovery Methods in Vectors by Metagenomic Sequencing

Identification and characterization of viral genomes in vectors including ticks and mosquitoes positive for pathogens of great public health concern using metagenomic next generation sequencing (mNGS) has challenges. One such challenge is the ability to efficiently recover viral RNA which is typically dependent on sample processing. We evaluated the quantitative effect of six different extraction methods in recovering viral RNA in vectors using negative tick homogenates spiked with serial dilutions of tick-borne encephalitis virus (TBEV) and surrogate Langat virus (LGTV). Evaluation was performed using qPCR and mNGS. Sensitivity and proof of concept of optimal method was tested using naturally positive TBEV tick homogenates and positive dengue, chikungunya, and Zika virus mosquito homogenates. The amount of observed viral genome copies, percentage of mapped reads, and genome coverage varied among different extractions methods. The developed Method 5 gave a 120.8-, 46-, 2.5-, 22.4-, and 9.9-fold increase in the number of viral reads mapping to the expected pathogen in comparison to Method 1, 2, 3, 4, and 6, respectively. Our developed Method 5 termed ROVIV (Recovery of Viruses in Vectors) greatly improved viral RNA recovery and identification in vectors using mNGS. Therefore, it may be a more sensitive method for use in arbovirus surveillance.

Infestation of an endemic arbovirus area by sympatric populations of Aedes aegypti and Aedes albopictus in Brazil

BACKGROUND Aedes aegypti and Aedes albopictus are the most important arbovirus vectors in the world. OBJECTIVES This study aimed to investigate and compare the infestation pattern of these species in a neighbourhood of Recife, Brazil, endemic for arboviruses in 2005 (T1) and 2013 (T2). METHODS Infestation, distribution and relative abundance of these sympatric species were recorded by egg collection using a network of 59 sentinel ovitraps (s-ovt) at fixed sampling stations for 12 months in T1 and T2. FINDINGS A permanent occupation pattern was detected which was characterised by the presence of egg-laying females of one or both species with a high ovitrap positivity index (94.3 to 100%) throughout both years analysed. In terms of abundance, the total of eggs collected was lower (p < 0.005) in T2 (146,153) than in T1 (281,103), although ovitraps still displayed a high index of positivity. The spatial distribution showed the presence of both species in 65.1% of the 148 s-ovt assessed, while a smaller number of traps exclusively contained Ae. aegypti (22%) or Ae. albopictus (13.2%) eggs. MAIN CONCLUSIONS Our comparative analysis demonstrated the robustness of the spatial occupation and permanence of Ae. aegypti and Ae. albopictus populations in this endemic urban area.

Vector competence of Culex mosquitoes (Diptera: Culicidae) in Zika virus transmission: an integrative review

OBJECTIVE

To identify studies on the competence of Culex mosquitoes as vectors for the transmission of Zika virus (ZIKV) around the globe.

METHODS

We performed an integrative review to identify relevant articles on specific experiments to determine whether Culex mosquitoes are vectors for ZIKV. The sources we used for our research were the Brazilian Periódicos CAPES electronic portal (MEDLINE/PubMed, ScienceDirect Journals, Nature Publishing Group, SciELO, Springer Link, and 250 other databases) and gray literature.

RESULTS

We identified 344 studies, of which 36 were considered for this review. In 8 studies, infection in salivary glands of Culex quinquefasciatus, Culex restuans, Culex tarsalis, and Culex coronator was detected. Cx. quinquefasciatus was the most studied among those confirmed as potential ZIKV vectors, and only strains of Asian lineages (THA/2014/SV0127-14; SZ01 (2016)) and American lineages (BRPE243 (2015); PRVABC59 (2015)) can infect the salivary glands of Culex mosquitoes. The tested African strains (MR766 and DAK AR 41525) were unable to infect salivary glands.

CONCLUSIONS

There is still a lack of compelling evidence that indicates Culex spp. are a competent ZIKV vector, but they should remain a target for further monitoring studies, especially regarding ZIKV transmission to other species. Furthermore, studies should not be limited to studying whether their salivary glands are infected.

Sequencing of ZIKV genomes directly from Ae. aegypti and Cx. quinquefasciatus mosquitoes collected during the 2015-16 epidemics in Recife

Zika virus (ZIKV) is a negative sense RNA virus from the Flaviviridae family, which was relatively unknown until the first human epidemic in Micronesia, in 2007. Since then, it spread to French Polynesia and the Americas. Recife, the capital of Pernambuco state and epicenter of the Zika epidemic in Brazil, experienced a large number of microcephaly cases and other congenital abnormalities associated to the ZIKV infection from, 2015 to 16. Evidences suggest that both Aedes aegypti and Culex quinquefasciatus mosquitoes from Recife are capable of replicating and transmitting the virus. Here, we conducted high throughput sequencing of ZIKV genomes directly from Ae. aegypti and Cx. quinquefasciatus mosquitoes collected during the ZIKV epidemics in Recife, in order to investigate the variability and evolution of the virus. We obtained 11 draft ZIKV genomes derived from 5 pools from each Ae. aegypti and Cx. quinquefasciatus species. Genome coverage breadth ranged from 16 to 100% and average depth from 45 to 46,584×. Two of these genomes were obtained from pools of Cx. quinquefasciatus females with no sign of blood in the abdomen. Amino acid substitutions found here were not species-specific. In addition, molecular clock dating estimated that ZIKV draft genomes obtained here were co-circulating in other regions of the country during the epidemics. Overall results highlight that viral mutations and even minor variants can be detected in genomes directly sequenced from mosquito samples and insights about natural viral genomic variability and viral evolution can be useful when designing tools for mosquito control programs.

Insecticide resistance in Culex quinquefasciatus Say, 1823 in Brazil: a review

Culex quinquefasciatus is a successful invasive species broadly distributed in subtropical regions, including Brazil. It is an extremely annoying mosquito due to its nocturnal biting behavior, in high-density populations and it is a potential bridge between sylvatic arbovirus from birds to man in urban territories. Herein, we present a review concerning the methods of chemical control employed against Cx. quinquefasciatus in Brazil since the 1950's and insecticide resistance data registered in the literature. As there is no specific national programme for Cx. quinquefasciatus control in Brazil, the selection of insecticide resistance is likely due in part to the well-designed chemical campaigns against Aedes aegypti and the elevated employment of insecticides by households and private companies. There are very few publications about insecticide resistance in Cx. quinquefasciatus from Brazil when compared to Ae. aegypti. Nevertheless, resistance to organophosphates, carbamate, DDT, pyrethroids and biolarvicides has been registered in Cx. quinquefasciatus populations from distinct localities of the country. Concerning physiological mechanisms selected for resistance, distinct patterns of esterases, as well as mutations in the acetylcholinesterase (ace-1) and voltage-gated sodium channel (NaV) genes, have been identified in natural populations. Given environmental changes and socioeconomical issues in the cities, in recent years we have been experiencing an increase in the number of disease cases caused by arboviruses, which may involve Cx. quinquefasciatus participation as a key vector. It is urgent to better understand the efficiency and susceptibility status to insecticides, as well as the genetic background of known resistant mechanisms already present in Cx. quinquefasciatus populations for an effective and rapid chemical control when eventually required.