Vector competence of Peruvian mosquitoes (Diptera: Culicidae) for a subtype IIIC virus in the Venezuelan equine encephalomyelitis complex isolated from mosquitoes captured in Peru

Revision of the Educator Group of Culex (Melanoconion) (Diptera, Culicidae)

The Educator Group of the Melanoconion Section of Culex (Melanoconion) (Diptera, Culicidae) is reviewed. Currently, the group includes the following valid species: Culex (Melanoconion) aphyllusTalaga, 2020, Culex (Melanoconion) cristovaoi Duret, 1968, Culex (Melanoconion) educatorDyar & Knab, 1906, Culex (Melanoconion) eknomiosForattini & Sallum, 1992, Culex (Melanoconion) inadmirabilisDyar, 1928, Culex (Melanoconion) rachoui Duret, 1968, Culex (Melanoconion) theobaldi (Lutz), 1904, Culex (Melanoconion) vaxusDyar, 1920, Culex (Melanoconion) angularis Sá & Sallum n. sp., Culex (Melanoconion) spiniformis Sá & Hutchings n. sp., Culex (Melanoconion) longistriatus Sá & Hutchings n. sp., Culex (Melanoconion) anelesDyar & Ludlow, 1922, Culex (Melanoconion) apeteticus Howard, Dyar & Ludlow, 1913, and Culex (Melanoconion) bibulusDyar, 1920. The last three species were resurrected from synonymy of either Cx. educator or Cx. vaxus. Descriptions, differential diagnoses, bionomics, and geographical data are provided for each species when available.

Evaluating sampling strategies for enzootic Venezuelan equine encephalitis virus vectors in Florida and Panama

Determining effective sampling methods for mosquitoes are among the first objectives in elucidating transmission cycles of vector-borne zoonotic disease, as the effectiveness of sampling methods can differ based on species, location, and physiological state. The Spissipes section of the subgenus Melanoconion of Culex represents an understudied group of mosquitoes which transmit Venezuelan equine encephalitis viruses (VEEV) in the Western Hemisphere. The objective of this study was to determine effective collection methods that target both blood-engorged and non-engorged females of the Spissipes section of Culex subgenus Melanoconion to test the hypothesis that favorable trapping methods differ between species and by physiological status within a species. Mosquitoes were collected using two commercially available traps, (CDC-light trap and BG-Sentinel trap), two novel passive traps (a novel mosquito drift fence and pop-up resting shelters), and two novel aspirators, (a small-diameter aspirator and a large-diameter aspirator) in Darién, Panama, and Florida, USA. The total number of female mosquitoes collected for each species was compared using rarefaction curves and diversity metrics. We also compared the utility of each trap for collecting total females and blood-engorged females of four Spissipes section mosquito species in Florida and Darién. In Darién, it was found that both blood-engorged and unfed females of Cx. pedroi were most effectively collected using the mosquito drift fence at 57.6% and 61.7% respectively. In contrast, the most unfed Cx. spissipes were collected using the mosquito drift fence (40.7%) while blood-engorged females were collected effectively by pop-up resting shelters (42.3%). In Florida, the best sampling technique for the collection of blood-engorged Cx. panocossa was the large diameter aspirator at 41.9%, while the best trap for collecting Cx. cedecei was the pop-up resting shelter at 45.9%. For unfed female Spissipes section mosquitoes in Florida, the CDC light trap with CO₂ collected 84.5% and 98.3% of Cx. cedecei and Cx. panocossa respectively in Florida. Rarefaction analysis, and both the Shannon and Simpsons diversity indices all demonstrated that the mosquito drift fence was capable of collecting the greatest diversity of mosquito species regardless of location. The finding that the proportions of unfed and blood-engorged mosquitoes collected by traps differed both among and between species has implications for how studies of VEEV vectors will be carried out in future investigations. In Florida a combination of pop-up resting shelters and use of a large-diameter aspirator would be optimal for the collection of both VEEV vectors for host-use studies. Results demonstrate that traps can be constructed from common materials to collect mosquitoes for VEEV vector studies and could be assessed for their utilization in vectors of other systems as well. Unfortunately, no single method was effective for capturing all species and physiological states, highlighting a particular need for assessing trap utility for target species of a study.

Venezuelan equine encephalitis virus is a potentially deadly human pathogen that is transmitted by an understudied group of tropical mosquitoes (Spissipes section of the Culex subgenus Melanoconion). These mosquitoes reside in swamps and jungles, and are challenging to identify, so studying their biology and importance in transmitting VEEV has been neglected. To further our understanding of VEEV, we compared six novel and commercially available traps to determine which traps are best for capturing these species in Panama and Florida. We found that several different types of traps are effective for collecting blood-engorged females of different species of VEEV vectors, and that traps utilized for collecting unfed specimens are not necessarily the same traps one should use for collecting blood-engorged females of the same species. Results of this study will enable researchers to better capture these important disease vectors, particularly those that are blood-engorged, which will allow researchers to determine host associations necessary for understanding VEEV transmission. This information can be used to make decisions on controlling vector species.

Isolation of a novel insect-specific flavivirus with immunomodulatory effects in vertebrate systems

We describe the isolation and characterization of a novel insect-specific flavivirus (ISFV), tentatively named Aripo virus (ARPV), that was isolated from Psorophora albipes mosquitoes collected in Trinidad. The ARPV genome was determined and phylogenetic analyses showed that it is a dual host associated ISFV, and clusters with the main mosquito-borne flaviviruses. ARPV antigen was significantly cross-reactive with Japanese encephalitis virus serogroup antisera, with significant cross-reactivity to Ilheus and West Nile virus (WNV). Results suggest that ARPV replication is limited to mosquitoes, as it did not replicate in the sandfly, culicoides or vertebrate cell lines tested. We also demonstrated that ARPV is endocytosed into vertebrate cells and is highly immunomodulatory, producing a robust innate immune response despite its inability to replicate in vertebrate systems. We show that prior infection or coinfection with ARPV limits WNV-induced disease in mouse models, likely the result of a robust ARPV-induced type I interferon response.

Mosquitoes (Diptera: Culicidae) From the Southwestern Brazilian Amazon: Liberdade and Gregório Rivers

The mosquito community from remote locations toward the southern border of the Brazilian State of Amazonas, in four localities along the Liberdade and Gregório Rivers, was sampled using CDC and Malaise traps, complemented with net sweeping and immature collections. During May 2011, 190 collections yielded 13,012 mosquitoes, from 15 genera and 112 different species, together with 10 morphospecies, which may represent new undescribed taxa. Among the species collected, there are two new geographical distribution records for the State of Amazonas. Culex, the most abundant genus, also had the highest number of species. Both Aedes and Uranotaenia had the second highest number of species, although they were the second and seventh most abundant, respectively. The most abundant species were Aedes (Ochlerotatus) fulvus (Wiedemann), Aedes (Ochlerotatus) nubilus (Theobald), Culex (Culex) mollis Dyar & Knab, Nyssorhynchus (Nyssorhynchus) oswaldoi sensu lato, Culex (Melanoconion) pedroi Sirivanakarn & Belkin, and Culex (Melanoconion) gnomatos Sallum, Hutchings & Ferreira. The epidemiological implications of mosquito species are discussed and compared with other mosquito inventories from the Amazon region. These results represent the first standardized mosquito inventories of the Liberdade and Gregório Rivers, with the identification of 112 species and 10 morphospecies, within the municipalities of Ipixuna and Eirunepé, from which we have only few records in the published literature.

Revision of the Atratus Group of Culex (Melanoconion) (Diptera: Culicidae)

BACKGROUND

Despite the importance of some species of Culex (Melanoconion) (Diptera: Culicidae) as vectors of several arboviruses that cause diseases in humans and other animals, there are few taxonomic studies focusing on species of the subgenus, especially providing morphological keys for species identification.

RESULTS

Thirteen species of the Atratus Group of Culex (Melanoconion) were reviewed, five new species are described, and two taxonomic changes are proposed: Cx. (Mel.) exedrus Root, 1927 and Cx. (Mel.) loturus Dyar, 1925 are resurrected from synonymy with Cx. (Mel.) dunni Dyar, 1918 and Cx. (Mel.) zeteki Dyar, 1918, respectively. The Atratus Group now includes fourteen species: Cx. (Mel.) atratus Theobald, 1901; Cx. (Mel.) caribeanus Galindo & Blanton, 1954; Cx. (Mel.) columnaris Sá & Hutchings n. sp.; Cx. (Mel.) commevynensis Bonne-Wepster & Bonne, 1919; Cx. (Mel.) comptus Sá & Sallum n. sp.; Cx. (Mel.) dunni; Cx. (Mel.) ensiformis Bonne-Wepster & Bonne, 1919; Cx. (Mel.) exedrus; Cx. (Mel.) longisetosus Sá & Sallum n. sp.; Cx. (Mel.) longistylus Sá & Sallum n. sp.; Cx. (Mel.) loturus; Cx. (Mel.) spinifer Sá & Sallum n. sp.; Cx. (Mel.) trigeminatus Clastrier, 1970; and Cx. (Mel.) zeteki. Keys, descriptions and illustrations for the identification of the male, female, pupal and fourth-instar larval stages of each species are provided. The treatment of each species includes a complete synonymy, descriptions of available life stages, a taxonomic discussion, updated bionomics and geographical distribution, and a list of material examined.

CONCLUSIONS

The taxonomy of the Atratus Group of Culex (Melanoconion) is updated, including descriptions of five new species. The number of valid species is greater than the number recognized in the previous taxonomic study of the group, increasing from seven to 14 species. Distributional and bionomical data are updated. Morphology-based identification keys for females, males, fourth-instar larvae and pupae provided in this study will facilitate species identification.

Mosquitoes (Diptera: Culicidae) From the Northwestern Brazilian Amazon: Araçá River

The mosquito fauna (Diptera: Culicidae) from two remote localities along the Araçá River, within the Municipality of Barcelos, towards the northern border of the Brazilian State of Amazonas, were sampled using CDC, Shannon, Malaise, and Suspended traps, along with net sweeping and immature collections. During June 2010, 111 collections yielded more than 23,500 mosquitoes distributed in 15 genera, representing 119 different species, together with eight morphospecies, which may represent undescribed new taxa. Among the species collected, there is one new distributional record for Brazil and nine new distributional records for the State of Amazonas. With the highest number of species, the genus Culex Linnaeus also had the largest number of individuals followed by Aedes Meigen with the second highest number of species. The most abundant species was Culex (Melanoconion) gnomatos Sallum, Hutchings & Ferreira followed by Culex (Melanoconion) portesi Senevet & Abonnenc, Culex (Culex) mollis Dyar & Knab, Aedes (Ochlerotatus) fulvus (Wiedemann), Culex (Melanoconion) pedroi Sirivanakarn & Belkin, Culex (Melanoconion) crybda Dyar, Aedes (Ochlerotatus) nubilus (Theobald), and Anopheles (Anopheles) peryassui Dyar & Knab. The epidemiological implications of mosquito species found are discussed and are compared with other mosquito inventories from the Amazon region. As the first standardized mosquito inventory of the Araçá River, with the identification of 127 species level taxa, the number of mosquito species which have been collected along the northern tributaries of the middle Rio Negro Basin (i.e., Padauari and Araçá Rivers) increased significantly.

Molecular phylogeny of Culex subgenus Melanoconion (Diptera: Culicidae) based on nuclear and mitochondrial protein-coding genes

The subgenus Melanoconion of the mosquito genus Culex is taxonomically diverse and is widely distributed in the Neotropical Region, with 10 species occurring in the Nearctic Region. Species of this subgenus pose a taxonomical challenge because morphological identification is based largely on anatomical characters of the male genitalia. We addressed the monophyly of the Spissipes and Melanoconion Sections of the subgenus Melanoconion and some of the informal groups in each section. Our sample taxa included 97 specimens representing 43 species, from which we analysed fragments of two single-copy nuclear genes (CAD, HB) and one mitochondrial gene (COI). Phylogenetic relationships within the subgenus are presented based on results of maximum-likelihood and Bayesian analyses using a multi-locus matrix of DNA sequences. We show a molecular phylogeny of Melanoconion in which both sections were recovered as monophyletic groups. The monophyly of the Atratus and Pilosus groups was confirmed. Within each section, other monophyletic groups were recovered highlighting the potential need for future nomenclature rearrangement. The phylogenetic signal contained in nuclear genes, when analysed together, was more informative than each gene analysed separately, corroborating monophyly of Melanoconion relative to Culex (Culex) species included in the analyses, the Melanoconion and Spissipes Sections and some species groups. Our results provide new information for the classification of the subgenus and additional data that can be used to improve species identification when a more representative taxon sampling is available.

Vector-borne diseases

After a request from the European Commission, EFSA's Panel on Animal Health and Welfare summarised the main characteristics of 36 vector‐borne diseases (VBDs) in https://efsa.maps.arcgis.com/apps/PublicGallery/index.html?appid=dfbeac92aea944599ed1eb754aa5e6d1. The risk of introduction in the EU through movement of livestock or pets was assessed for each of the 36 VBDs individually, using a semiquantitative Method to INTegrate all relevant RISK aspects (MINTRISK model), which was further modified to a European scale into the http://www3.lei.wur.nl/mintrisk/ModelMgt.aspx. Only eight of the 36 VBD‐agents had an overall rate of introduction in the EU (being the combination of the rate of entry, vector transmission and establishment) which was estimated to be above 0.001 introductions per year. These were Crimean‐Congo haemorrhagic fever virus, bluetongue virus, West Nile virus, Schmallenberg virus, Hepatozoon canis, Leishmania infantum, Bunyamwera virus and Highlands J. virus. For these eight diseases, the annual extent of spread was assessed, assuming the implementation of available, authorised prevention and control measures in the EU. Further, the probability of overwintering was assessed, as well as the possible impact of the VBDs on public health, animal health and farm production. For the other 28 VBD‐agents for which the rate of introduction was estimated to be very low, no further assessments were made. Due to the uncertainty related to some parameters used for the risk assessment or the instable or unpredictability disease situation in some of the source regions, it is recommended to update the assessment when new information becomes available. Since this risk assessment was carried out for large regions in the EU for many VBD‐agents, it should be considered as a first screening. If a more detailed risk assessment for a specific VBD is wished for on a national or subnational level, the EFSA‐VBD‐RISK‐model is freely available for this purpose.

Mitochondrial COI gene as a tool in the taxonomy of mosquitoes Culex subgenus Melanoconion

The subgenus Melanoconion is the second largest subgenus within the genus Culex, with 160 described species. Several of the species are proven vectors of arboviruses, including West Nile virus, Venezuelan equine encephalitis virus complex and Eastern equine encephalomyelitis virus. Species of Melanoconion are well distributed from southern North America to most countries of South America and display the highest species diversity in tropical regions. Taxonomical identification within this group has been primarily based on morphological characters, with the male genitalia as the source of the most solid diagnostic features. The difficulty in reaching accurate species determinations when studying specimens of Culex (Melanoconion) has been extensively documented as a real limitation to expand knowledge of these insects. We tested the utility of the mitochondrial gene COI as a complementary tool in the taxonomy of Melanoconion. Using a data set of 120 COI sequences from Culex specimen captured in several localities in Brazil, the utility of COI barcodes for species delimitation is discussed through the evaluation of genetic divergences among specimens and the clustering patterns of species in three topologies obtained with Neighbor Joining, Maximum Likelihood and Bayesian phylogenetic inference. For all specimens included in this study a previous morphological examination was performed, and most of the taxonomical determinations were corroborated using the COI barcode. We generated COI sequences that belong to 48 species of Melanoconion, with a mean intraspecific K2P genetic divergence of 3%; and all interspecific divergence values higher than the intraspecific divergence values. This is the first comprehensive study of subgenus Melanoconion, with evidence of COI as a useful and accessible DNA barcode.

Mosquitoes (Diptera: Culicidae) From the Northwestern Brazilian Amazon: Padauari River

The mosquito fauna (Culicidae) from remote northern areas of the State of Amazonas were sampled using Centers for Disease Control and Prevention, Shannon, Malaise, and Suspended traps, together with net sweeping and immature collections. One hundred and seven collections were performed in five localities along the Padauari River, State of Amazonas, Brazil, during June 2010. The 20,557 mosquitoes collected are distributed in 17 genera, representing 117 different species, of which four are new distributional records for the State of Amazonas. Furthermore, there are 10 morphospecies that may represent undescribed new taxa, eight of which are also new records for the State of Amazonas. The genus Culex had the highest number of species and the largest number of individuals. Aedes and Psorophora both represented 10% of the total sample and had the second highest number of species and individuals. The most abundant species was Culex (Melanoconion) gnomatos Sallum, Hutchings & Ferreira, followed by Aedes (Ochlerotatus) fulvus (Wiedemann), Culex (Melanoconion) vaxus Dyar, Culex (Melanoconion) portesi Senevet & Abonnenc, Psorophora (Janthinosoma) amazonica Cerqueira, Culex (Culex) mollis Dyar & Knab, Psorophora (Janthinosoma) albigenu (Peryassú), and Culex (Melanoconion) theobaldi Lutz. The epidemiological and ecological implications of mosquito species found are discussed and are compared with other mosquito inventories from the Amazon region. The results represent the most diverse standardized inventory of mosquitoes along the Padauari River, with the identification of 127 species-level taxa distributed in five localities, within two municipalities (Barcelos and Santa Isabel do Rio Negro).

The role of environmental, virological and vector interactions in dictating biological transmission of arthropod-borne viruses by mosquitoes

Arthropod-borne viruses (arboviruses) are transmitted between vertebrate hosts and arthropod vectors. An inherently complex interaction among virus, vector, and the environment determines successful transmission of the virus. Once believed to be "flying syringes," recent advances in the field have demonstrated that mosquito genetics, microbiota, salivary components, and mosquito innate immune responses all play important roles in modulating arbovirus transmissibility. The literature on the interaction among virus, mosquito, and environment has expanded dramatically in the preceding decade and the utilization of next-generation sequencing and transgenic vector methodologies assuredly will increase the pace of knowledge acquisition in this field. This chapter outlines the interplay among the three factors in both direct physical and biochemical manners as well as indirectly through superinfection barriers and altered induction of innate immune responses in mosquito vectors. The culmination of the aforementioned interactions and the arms race between the mosquito innate immune response and the capacity of arboviruses to antagonize such a response ultimately results in the subjugation of mosquito cells for viral replication and subsequent transmission.

A deep insight into the sialotranscriptome of the mosquito, Psorophora albipes

Background

Psorophora mosquitoes are exclusively found in the Americas and have been associated with transmission of encephalitis and West Nile fever viruses, among other arboviruses. Mosquito salivary glands represent the final route of differentiation and transmission of many parasites. They also secrete molecules with powerful pharmacologic actions that modulate host hemostasis, inflammation, and immune response. Here, we employed next generation sequencing and proteome approaches to investigate for the first time the salivary composition of a mosquito member of the Psorophora genus. We additionally discuss the evolutionary position of this mosquito genus into the Culicidae family by comparing the identity of its secreted salivary compounds to other mosquito salivary proteins identified so far.

Results

Illumina sequencing resulted in 13,535,229 sequence reads, which were assembled into 3,247 contigs. All families were classified according to their in silico-predicted function/ activity. Annotation of these sequences allowed classification of their products into 83 salivary protein families, twenty (24.39%) of which were confirmed by our subsequent proteome analysis. Two protein families were deorphanized from Aedes and one from Ochlerotatus, while four protein families were described as novel to Psorophora genus because they had no match with any other known mosquito salivary sequence. Several protein families described as exclusive to Culicines were present in Psorophora mosquitoes, while we did not identify any member of the protein families already known as unique to Anophelines. Also, the Psorophora salivary proteins had better identity to homologs in Aedes (69.23%), followed by Ochlerotatus (8.15%), Culex (6.52%), and Anopheles (4.66%), respectively.

Conclusions

This is the first sialome (from the Greek sialo = saliva) catalog of salivary proteins from a Psorophora mosquito, which may be useful for better understanding the lifecycle of this mosquito and the role of its salivary secretion in arboviral transmission.

Endemic Venezuelan equine encephalitis in the Americas: hidden under the dengue umbrella

Venezuelan equine encephalitis (VEE) is an emerging infectious disease in Latin America. Outbreaks have been recorded for decades in countries with enzootic circulation, and the recent implementation of surveillance systems has allowed the detection of additional human cases in countries and areas with previously unknown VEE activity. Clinically, VEE is indistinguishable from dengue and other arboviral diseases and confirmatory diagnosis requires the use of specialized laboratory tests that are difficult to afford in resource-limited regions. Thus, the disease burden of endemic VEE in developing countries remains largely unknown, but recent surveillance suggests that it may represent up to 10% of the dengue burden in neotropical cities, or tens-of-thousands of cases per year throughout Latin America. The potential emergence of epizootic viruses from enzootic progenitors further highlights the need to strengthen surveillance activities, identify mosquito vectors and reservoirs and develop effective strategies to control the disease. In this article, we provide an overview of the current status of endemic VEE that results from spillover of the enzootic cycles, and we discuss public health measures for disease control as well as future avenues for VEE research.

Endemic Venezuelan equine encephalitis in the Americas: hidden under the dengue umbrella

Venezuelan equine encephalitis (VEE) is an emerging infectious disease in Latin America. Outbreaks have been recorded for decades in countries with enzootic circulation, and the recent implementation of surveillance systems has allowed the detection of additional human cases in countries and areas with previously unknown VEE activity. Clinically, VEE is indistinguishable from dengue and other arboviral diseases and confirmatory diagnosis requires the use of specialized laboratory tests that are difficult to afford in resource-limited regions. Thus, the disease burden of endemic VEE in developing countries remains largely unknown, but recent surveillance suggests that it may represent up to 10% of the dengue burden in neotropical cities, or tens-of-thousands of cases per year throughout Latin America. The potential emergence of epizootic viruses from enzootic progenitors further highlights the need to strengthen surveillance activities, identify mosquito vectors and reservoirs and develop effective strategies to control the disease. In this article, we provide an overview of the current status of endemic VEE that results from spillover of the enzootic cycles, and we discuss public health measures for disease control as well as future avenues for VEE research.

Seasonal distribution, biology, and human attraction patterns of mosquitoes (Diptera: Culicidae) in a rural village and adjacent forested site near Iquitos, Peru

This study was conducted as part of a field-ecology study of arboviral and malarial activity in the Amazon Basin, Loreto Department, Peru, to determine the relative abundance, species diversity, and seasonal and vertical distributions of potential mosquito vectors. Mosquitoes were captured either by volunteers using mouth aspirators while mosquitoes attempted to land on the collectors or in dry ice-baited ABC light traps. Anopheles darlingi, the principal malaria vector in the region, was the most commonly captured anopheline mosquito in Puerto Almendra village (99%) while landing on humans, with a mean of 37.1 mosquitoes captured per 24-h period, representing nearly one half of all mosquitoes collected. An. darlingi human landing activity began shortly after sunset, peaked at 2000-2100 hours, and declined gradually until sunrise. This species readily entered houses, because 51% of the An. darlingi captured by paired collectors, stationed inside and outside houses, were captured indoors. Human landing collections provided a more accurate estimate of human attraction of An. darlingi, capturing 30 times as many as co-located dry ice-baited ABC light traps. In contrast, eight times as many Culex (Melanoconion) species, including known arbovirus vectors, were captured in light traps as by co-located human collectors. Despite being located within 300 m of the village collection site, only a few Anopheles species were captured at the forest collection site, including only 0.1 An darlingi/ 24 h, thus indicating that An. darlingi activity was directly associated with the rural village. These data provide a better understanding of the taxonomy, population density, and seasonal distribution of potential mosquito vectors of disease within the Amazon Basin region and allow for the development of appropriate vector and disease prevention strategies that target vector populations.

Cloning and overexpression of ribosomal protein L39 gene from deltamethrin-resistant Culex pipiens pallens

The complete sequence of ribosomal protein L39 has been cloned from deltamethrin-resistant strain of Culex pipiens pallens (DR1 strain). Quantitative RT-PCR analysis indicated that the RPL39 transcription level was 23.4 times higher in DR1 strain than in susceptible strain at 4th instar larvae. The RPL39 expression was also found to be consistently higher throughout the life cycle of DR1 strain. A protein of predicted size 17 kDa has been detected by Western blotting in RPL39-transfected mosquito C6/36 cells. These RPL39-transfected cells also showed enhanced deltamethrin resistance compared to plasmid vector-transfected cells as determined by methyl tritiated thymidine ((3)H-TdR) incorporation. These results indicate that RPL39 is expressed at higher levels in DR1 strain, and may confer some insecticide resistance in Cx. pipiens pallens.