Mayaro virus, a potential threat for Europe: vector competence of autochthonous vector species.

BACKGROUND: Mayaro virus (MAYV) is an emerging alphavirus, primarily transmitted by the mosquito Haemagogus janthinomys in Central and South America. However, recent studies have shown that Aedes aegypti, Aedes albopictus and various Anopheles mosquitoes can also transmit the virus under laboratory conditions. MAYV causes sporadic outbreaks across the South American region, particularly in areas near forests. Recently, cases have been reported in European and North American travelers returning from endemic areas, raising concerns about potential introductions into new regions. This study aims to assess the vector competence of three potential vectors for MAYV present in Europe. METHODS: Aedes albopictus from Italy, Anopheles atroparvus from Spain and Culex pipiens biotype molestus from Belgium were exposed to MAYV and maintained under controlled environmental conditions. Saliva was collected through a salivation assay at 7 and 14 days post-infection (dpi), followed by vector dissection. Viral titers were determined using focus forming assays, and infection rates, dissemination rates, and transmission efficiency were calculated. RESULTS: Results indicate that Ae. albopictus and An. atroparvus from Italy and Spain, respectively, are competent vectors for MAYV, with transmission possible starting from 7 dpi under laboratory conditions. In contrast, Cx. pipiens bioform molestus was unable to support MAYV infection, indicating its inability to contribute to the transmission cycle. CONCLUSIONS: In the event of accidental MAYV introduction in European territories, autochthonous outbreaks could potentially be sustained by two European species: Ae. albopictus and An. atroparvus. Entomological surveillance should also consider certain Anopheles species when monitoring MAYV transmission.

A metagenomic analysis of the phase 2 Anopheles gambiae 1000 genomes dataset reveals a wide diversity of cobionts associated with field collected mosquitoes.

The Anopheles gambiae 1000 Genomes (Ag1000G) Consortium previously utilized deep sequencing methods to catalogue genetic diversity across African An. gambiae populations. We analyzed the complete datasets of 1142 individually sequenced mosquitoes through Microsoft Premonition's Bayesian mixture model based (BMM) metagenomics pipeline. All specimens were confirmed as either An. gambiae sensu stricto (s.s.) or An. coluzzii with a high degree of confidence ( > 98% identity to reference). Homo sapiens DNA was identified in all specimens indicating contamination may have occurred either at the time of specimen collection, preparation and/or sequencing. We found evidence of vertebrate hosts in 162 specimens. 59 specimens contained validated Plasmodium falciparum reads. Human hepatitis B and primate erythroparvovirus-1 viral sequences were identified in fifteen and three mosquito specimens, respectively. 478 of the 1,142 specimens were found to contain bacterial reads and bacteriophage-related contigs were detected in 27 specimens. This analysis demonstrates the capacity of metagenomic approaches to elucidate important vector-host-pathogen interactions of epidemiological significance.

Spatial patterns of West Nile virus distribution in the Volgograd region of Russia, a territory with long-existing foci.

Southern Russia remains affected by West Nile virus (WNV). In the current study, we identified the spatial determinants of WNV distribution in an area with endemic virus transmission, with special reference to the urban settings, by mapping probable points of human infection acquisition and points of virus detection in mosquitoes, ticks, birds, and mammals during 1999-2016. The suitability of thermal conditions for extrinsic virus replication was assessed based on the approach of degree-day summation and their changes were estimated by linear trend analysis. A generalized linear model was used to analyze the year-to-year variation of human cases versus thermal conditions. Environmental suitability was determined by ecological niche modelling using MaxEnt software. Human population density was used as an offset to correct for possible bias. Spatial analysis of virus detection in the environment showed significant contributions from surface temperature, altitude, and distance from water bodies. When indicators of location and mobility of the human population were included, the relative impact of factors changed, with roads becoming most important. When the points of probable human case infection were added, the percentage of leading factors changed only slightly. The urban environment significantly increased the epidemic potential of the territory and created quite favorable conditions for virus circulation. The private building sector with low-storey houses and garden plots located in the suburbs provided a connection between urban and rural transmission cycles.

Detection of Insect-Specific Flaviviruses in Mosquitoes (Diptera: Culicidae) in Northeastern Regions of South Africa.

Mosquitoes in the Aedes and Culex genera are considered the main vectors of pathogenic flaviviruses worldwide. Entomological surveillance using universal flavivirus sets of primers in mosquitoes can detect not only pathogenic viruses but also insect-specific ones. It is hypothesized that insect-specific flaviviruses, which naturally infect these mosquitoes, may influence their vector competence for zoonotic arboviruses. Here, entomological surveillance was performed between January 2014 and May 2018 in five different provinces in the northeastern parts of South Africa, with the aim of identifying circulating flaviviruses. Mosquitoes were sampled using different carbon dioxide trap types. Overall, 64,603 adult mosquitoes were collected, which were screened by RT-PCR and sequencing. In total, 17 pools were found positive for insect-specific Flaviviruses in the mosquito genera Aedes (12/17, 70.59%) and Anopheles (5/17, 29.41%). No insect-specific viruses were detected in Culex species. Cell-fusing agent viruses were detected in Aedes aegypti and Aedes caballus. A range of anopheline mosquitoes, including Anopheles coustani, An. squamosus and An. maculipalpis, were positive for Culex flavivirus-like and Anopheles flaviviruses. These results confirm the presence of insect-specific flaviviruses in mosquito populations in South Africa, expands their geographical range and indicates potential mosquito species as vector species.

Human and plant volatiles; lures for mosquito, vectors of dengue virus and malaria.

Increased outbreaks of mosquito borne diseases like the deadly parasitic disease, malaria and arboviruses like Zika, yellow fever and dengue viruses around the world have led to increased interest in traps that could effectively be used against mosquitoes. For example, a Google search at the time of this writing, asking, 'which is the best way of trapping mosquitoes?' produced 35.5 million search results. Regardless of the interest in the subject, scientists have yet to find a definitive answer to these questions. One area that has been exploited as a potential source of efficient traps for mosquitoes is host odour baits. Since mosquitoes are attracted to their hosts through odours produced by the hosts, it's highly likely that synthetic chemical blends based on host odours could provide a solution. Most mosquito species have 2 hosts: vertebrate animals and vascular plants. Amongst the vertebrates, most diseases spread by mosquitoes are to humans. Considerable research has therefore been conducted on human odours that elicit attraction in mosquitoes, with emphasis on compounds from sweat and skin. Interest on plant volatiles is currently gathering pace because unlike human odours that only attract host seeking female mosquitoes, plant odours can attract both male and female mosquitoes of all gonotrophic stages. This review article concentrates on some of the chemical compounds in human and plant host odours that have shown a potential as attractants to mosquitoes especially Aedes aegypti and Anopheles gambiae s.l.

An update on the mosquito fauna and mosquito-borne diseases distribution in Cameroon.

The expansion of mosquito-borne diseases such as dengue, yellow fever, and chikungunya in the past 15 years has ignited the need for active surveillance of common and neglected mosquito-borne infectious diseases. The surveillance should be designed to detect diseases and to provide relevant field-based data for developing and implementing effective control measures to prevent outbreaks before significant public health consequences can occur. Mosquitoes are important vectors of human and animal pathogens, and knowledge on their biodiversity and distribution in the Afrotropical region is needed for the development of evidence-based vector control strategies. Following a comprehensive literature search, an inventory of the diversity and distribution of mosquitoes as well as the different mosquito-borne diseases found in Cameroon was made. A total of 290 publications/reports and the mosquito catalogue website were consulted for the review. To date, about 307 species, four subspecies and one putative new species of Culicidae, comprising 60 species and one putative new species of Anopheles, 67 species and two subspecies of Culex, 77 species and one subspecies of Aedes, 31 species and one subspecies of Eretmapodites, two Mansonia, eight Coquillettidia, and 62 species with unknown medical and veterinary importance (Toxorhynchites, Uranotaenia, Mimomyia, Malaya, Hodgesia, Ficalbia, Orthopodomyia, Aedeomyia, and Culiseta and Lutzia) have been collected in Cameroon. Multiple mosquito species implicated in the transmission of pathogens within Anopheles, Culex, Aedes, Eretmapodites, Mansonia, and Coquillettidia have been reported in Cameroon. Furthermore, the presence of 26 human and zoonotic arboviral diseases, one helminthic disease, and two protozoal diseases has been reported. Information on the bionomics, taxonomy, and distribution of mosquito species will be useful for the development of integrated vector management programmes for the surveillance and elimination of mosquito-borne diseases in Cameroon.

Host selection pattern and flavivirus screening of mosquitoes in a disturbed Colombian rainforest.

Studies on the feeding behavior of hematophagous insects, particularly those of medical importance, are relevant for tracking possible pathogen transmission routes and identifying biases in the choice of vertebrates. We evaluated host selection of blood-feeding mosquitoes in a disturbed forest in the Magdalena Medio valley in Colombia from March 2017 to April 2018, after the introduction of Zika virus to the Americas from the 2015-2016 outbreak. We estimated vertebrate diversity and collected blood-engorged female mosquitoes. Genomic DNA/RNA was extracted from the mosquito's abdomen for vertebrate host identification and pathogen detection. We performed conventional PCR and sequencing, using universal primers targeting vertebrate regions of the eukaryotic mitochondrial genome to determine bloodmeal host. Additionally, we tested for the presence of flaviviruses in all mosquito samples with RT-PCR. Based on the identity and quantity of detected bloodmeals, we performed mosquito-vertebrate interaction network analysis and estimated topology metrics. In total, we collected 292 engorged female mosquitoes representing 20 different species. Bloodmeal analyses identified 26 vertebrate species, the majority of which were mammals (N = 16; 61.5%). No flaviviruses of medical importance were detected from the samples. Although feeding patterns varied, network analyses showed a high degree of specialization by mosquitoes and revealed ecological and phylogenetic relationships among the host community. We conclude that host selection or preference by mosquitoes is species specific.

Screening for Viruses and Lemur-Associated Filara in Wild-Caught Mosquitoes From Madagascar.

Madagascar is a hotspot of biodiversity, but poverty and population growth provoke a high risk of conflict between food security and biodiversity conservation in this tropical country. Numerous vector-borne diseases, including viral infections, affect public health in Madagascar and a continuous expansion of anthropogenically used areas intensifies contact on the human-wildlife interface. However, data on human and animal pathogens in potential insect vectors is limited. Therefore, we conducted a parasitological and virological survey of 785 adult female mosquitoes between March and May 2016 at the Ankarafantsika National Park in northwestern Madagascar. Screening included Alpha-, Phlebo-, and Flaviviridae and the recently described filarial nematode species, Lemurfilaria lemuris. The predominant mosquito genus was Culex (91%), followed by Mansonia (4.1%), Anopheles (3.4%), and Aedes (0.9%). Viral screening revealed no arboviruses, but an insect-specific flavivirus in two Culex sitiens pools. No pools screened positive for the lemur-specific filarial nematode L. lemuris.

Emergence of Zika Virus in Culex tritaeniorhynchus and Anopheles sinensis Mosquitoes in China.

Zika virus (ZIKV) has been isolated from mosquitoes such as Aedes, Mansonia uniformis, and Culex perfuscus; However, the isolation of ZIKV from Anopheles sinensis and Culex tritaeniorhynchus has not yet been reported. In June and July 2018, 22,985 mosquitoes and 57,500 midges were collected in Jiangxi Province in southeastern China. Among them, six strains of ZIKV were isolated from mosquitoes: four from An. sinensis and two from Cx. tritaeniorhynchus. Molecular genetic analysis showed that the ZIKV isolated from An. sinensis and Cx. tritaeniorhynchus belonged to genotype 2 in the Asian evolutionary branch of ZIKV. In addition, the ZIKV strains isolated from An. sinensis and Cx. tritaeniorhynchus had amino acid substitutions identical to ZIKV strains prevalent in South America since 2015. This study is the first to isolate ZIKV from mosquito specimens collected in the wild of Jiangxi Province, China; This is also the first time that ZIKV has been isolated from An. sinensis and Cx. tritaeniorhynchus. Given that An. sinensis and Cx. tritaeniorhynchus have a very wide geographical distribution in China and even in eastern and southern Asia, the isolation of several strains of ZIKV from these two mosquitoes poses new challenges for the prevention and control of ZIKV infection in the mainland of China and countries and regions with the same distribution of mosquitoes.

Potential Mosquito Vectors of Dirofilaria immitis and Dirofilaira repens (Spirurida: Onchocercidae) in Aras Valley, Turkey.

Dirofilaria immitis (Leidy, 1856) and Dirofilaria repens (Railliet & Henry, 1911) are mosquito-borne filarial nematodes that primarily affect dogs, causing heartworm disease and subcutaneous dirofilariosis. The canine heartworm is reported in different provinces in Turkey. However, studies about the transmitting mosquito species are limited. Hence, this study aimed to investigate potential vectors of D. immitis and D. repens in Aras Valley, Turkey. In total, 17,995 female mosquitoes were collected from eight villages during three mosquito seasons (2012-2014) in Aras Valley, located in north-eastern Turkey. A total of 1,054 DNA pools (527 abdomen and 527 head-thorax) were tested with Dirofilaria primers by multiplex-polymerase chain reaction (PCR). Aedes caspius was the most abundant species in collection sites with 90%; this was followed by Culex theileri Theobald, 1903 (Diptera: Culicidae) (7.31%), Anopheles maculipennis Meigen 1818 (Diptera: Culicidae) (1.28%), Culex pipiens Linnaeus, 1758 (Diptera: Culicidae) (0.43%), (Anopheles) hyrcanus (Pallas, 1771) (Diptera: Culicidae) (0.37%), Aedes vexans (Meigen, 1830) (Diptera: Culicidae) (0.25%), and Culiseta annulata Schrank, 1776 (Diptera:Culicidae) (0.02%). Dirofilaria immitis and D. repens were detected in mosquito pools from five villages. The total Dirofilaria spp. estimated infection rate was 1.33%. The highest estimated infection rate was found in Ae. vexans (6.66%) and the lowest was in Ae. caspius (1.26%). The results show that An. maculipennis sl, Ae. caspius, Ae. vexans, Cx. theileri and Cx. pipiens are potential vectors of D. immitis and D. repens with DNA in head-thorax pools; An. hyrcanus is also a likely vector, but Dirofilaria DNA was found only in abdomen pools for the study area. This study revealed new potential vector species for D. immitis. Mosquitoes with natural infections of D. repens were reported for the first time in Turkey.

Transmission potential of Mayaro virus by Aedes albopictus, and Anopheles quadrimaculatus from the USA.

BACKGROUND: Mayaro virus (MAYV; Alphavirus, Togaviridae) is an emerging pathogen endemic in South American countries. The increase in intercontinental travel and tourism-based forest excursions has resulted in an increase in MAYV spread, with imported cases observed in Europe and North America. Intriguingly, no local transmission of MAYV has been reported outside South America, despite the presence of potential vectors. METHODS: We assessed the vector competence of Aedes albopictus from New York and Anopheles quadrimaculatus for MAYV. RESULTS: The results show that Ae. albopictus from New York and An. quadrimaculatus are competent vectors for MAYV. However, Ae. albopictus was more susceptible to infection. Transmission rates increased with time for both species, with rates of 37.16 and 64.44% for Ae. albopictus, and of 25.15 and 48.44% for An. quadrimaculatus, respectively, at 7 and 14 days post-infection. CONCLUSIONS: Our results suggest there is a risk of further MAYV spread throughout the Americas and autochthonous transmission in the USA. Preventive measures, such as mosquito surveillance of MAYV, will be essential for early detection.

Detection of Zika and dengue viruses in wild-caught mosquitoes collected during field surveillance in an environmental protection area in São Paulo, Brazil.

Species of the genus Flavivirus are widespread in Brazil and are a major public health concern. The country's largest city, São Paulo, is in a highly urbanized area with a few forest fragments which are commonly used for recreation. These can be considered to present a potential risk of flavivirus transmission to humans as they are home simultaneously to vertebrate hosts and mosquitoes that are potential flavivirus vectors. The aim of this study was to conduct flavivirus surveillance in field-collected mosquitoes in the Capivari-Monos Environmental Protection Area (EPA) and identify the flavivirus species by sequence analysis in flavivirus IFA-positive pools. Monthly mosquito collections were carried out from March 2016 to April 2017 with CO2-baited CDC light traps. Specimens were identified morphologically and grouped in pools of up to 10 individuals according to their taxonomic category. A total of 260 pools of non-engorged females were inoculated into C6/36 cell culture, and the cell suspensions were analyzed by indirect immunofluorescence assay (IFA) after the incubation period. IFA-positive pools were tested by qRT-PCR with genus-specific primers targeting the flavivirus NS5 gene to confirm IFA-positive results and sequenced to identify the species. Anopheles cruzii (19.5%) and Wyeomyia confusa (15.3%) were the most frequent vector species collected. IFA was positive for flaviviruses in 2.3% (6/260) of the sample pools. This was confirmed by qRT-PCR in five pools (83.3%). All five flavivirus-positive pools were successfully sequenced and the species identified. DENV serotype 2 (DENV-2) was detected in Culex spp. and Culex vaxus pools, while ZIKV was identified in An. cruzii, Limatus durhamii and Wy. confusa pools. To the best of our knowledge, detection of flavivirus species of medical importance has never previously been reported in these species of wild-caught mosquitoes. The finding of DENV-2 and ZIKV circulating in wild mosquitoes suggests the existence of an enzootic cycle in the area. In-depth studies of DENV-2 and ZIKV, including investigation of mosquito infection, vector competence and infection in sylvatic hosts, are needed to shed light on the transmission dynamics of these important viruses and the potential risk of future outbreaks of DENV-2 and ZIKV infections in the region.

Interactions between the imperiled West Indian manatee, Trichechus manatus, and mosquitoes (Diptera: Culicidae) in Everglades National Park, Florida, USA.

Arthropod-borne viruses (arboviruses), including those vectored by mosquitoes, have recently been cited as potential emerging health threats to marine mammals. Despite the fully aquatic habits of cetaceans, immunologic exposure to arboviruses including West Nile virus and Eastern equine encephalitis virus has been detected in wild Atlantic bottlenose dolphins, and captive orcas have been killed by West Nile virus and St. Louis encephalitis virus. Currently, there is no evidence of direct interactions between mosquitoes and marine mammals in nature, and it remains unknown how wild cetaceans are exposed to mosquito-vectored pathogens. Here, we report the first evidence of direct interactions between an aquatic mammal, the West Indian manatee, a federally threatened species, and mosquitoes in nature. Observations of manatees in Everglades National Park, Florida, USA, indicate that mosquitoes of three genera, Aedes, Anopheles, and Culex are able to locate and land on surface-active manatees, and at minimum, penetrate and probe manatee epidermis with their mouthparts. Whether mosquitoes can successfully take a blood meal is not known; however, an arbovirus-infected mosquito can inoculate extravascular host tissues with virus-infected saliva during probing. These observations suggest that it is possible for marine mammals to be exposed to mosquito-vectored pathogens through direct interactions with mosquitoes.

Anopheles gambiae densovirus (AgDNV) negatively affects Mayaro virus infection in Anopheles gambiae cells and mosquitoes.

BACKGROUND: Recent studies demonstrate that insect-specific viruses can influence the ability of their mosquito hosts to become infected with and transmit arboviruses of medical and veterinary importance. The aim of this study was to evaluate the interactions between Anopheles gambiae densovirus (AgDNV) (Parvoviridae) (a benign insect-specific virus that infects An. gambiae mosquitoes) and Mayaro virus (MAYV) (Togaviridae) (an emerging human pathogen that can be transmitted by An. gambiae) in both insect cell culture and mosquitoes. METHODS: For in vitro studies, An. gambiae Mos55 cells infected or uninfected with AgDNV were infected with MAYV. For in vivo studies, An. gambiae mosquitoes were injected intrathoracically with AgDNV and 4 days later orally infected with MAYV. Mosquitoes were dissected 10 days after MAYV infection, and MAYV titers in the body, legs and saliva samples quantified using focus-forming assay. RESULTS: MAYV virus replication was reduced 10-100-fold in An. gambiae Mos55 cells infected with AgDNV. In mosquitoes, there was a significant negative correlation between AgDNV and MAYV body titers 10 days post-blood meal. CONCLUSIONS: AgDNV infection was associated with reduced production of MAYV in cell culture, and reduced body titers of MAYV in An. gambiae mosquitoes. As densovirus infections are common in natural mosquito populations, these data suggest that they may affect the epidemiology of viruses of medical importance.

Seasonal variations of dengue vector mosquitoes in rural settings of Thiruvarur district in Tamil Nadu, India.

BACKGROUND & OBJECTIVES: Mosquitoes are vectors of several important vector-borne diseases (VBDs) like malaria, dengue, chikungunya, Japanese encephalitis (JE) and lymphatic filariasis (LF). Globally, these VBDs are of major public health concern including India. The information on vector mosquitoes from Thiruvarur district in Tamil Nadu state remains largely either unknown or undocumented. The present study was, therefore, undertaken to find out the seasonal variation in mosquitoes with special reference to dengue vectors in rural areas of Thiruvarur district, Tamil Nadu, India. METHODS: Surveillance of immature vector mosquitoes was undertaken from March 2018 to February 2019. The emerged adults were identified to find out the composition of mosquito species prevalent in the district. The seasonal variations of the mosquitoes especially dengue vectors were analysed for summer (March-July) spring (August-November) and winter (December-February) seasons in all the blocks of Thiruvarur district. RESULTS: A total of 4879 mosquitoes emerged from the immature collection and the species identification revealed the prevalence of both vector and non-vector species. Five important mosquito vectors collected were -Aedes albopictus, Ae. aegypti, Culex tritaeniorhynchus, Cx. gelidus, and Cx. quinquefasciatus. Other mosquito species collected were Lutzia fuscana, Anopheles barbirostris, An. subpictus, and Armigeres (Armigeres) subalbatus. During the spring season, the dengue vectors showed high indices of breateau index (BI), ranging from 16 to 120; besides, container index (CI) ranging from14.29 to 68.57 and pupal index (PI) from 53.33 to 295 among the study blocks. The major breeding sites were discarded plastic containers, discarded tyres, open sintex tanks (water storage tanks), cement tanks, discarded fibre box, pleated plastic sheets, tree holes, bamboo cut stumps, coconut spathe, and coconut shells. INTERPRETATION & CONCLUSION: The immature vector surveillance revealed seasonal variations in the entomological indices of Aedes breeding potential. The high indices observed indicate high Aedes breeding density and, therefore, a higher risk for dengue/chikungunya outbreaks in rural areas of Thiruvarur district. The present finding warrants intensive surveillance and follow up vector control measures to avert outbreaks and prevent vector-borne diseases. Health education and the community participation in awareness camps prior to monsoon and societal commitment will help in strengthening source reduction, anti-larval operations and anti-adult measures to tackle vector-borne diseases especially dengue.

A viral metagenomic analysis reveals rich viral abundance and diversity in mosquitoes from pig farms.

Mosquitoes harbour a diversity of viruses and are responsible for several mosquito-borne viral diseases of humans and animals, thereby leading to major public health concerns, and significant economic losses across the globe. Viral metagenomics offers a great opportunity for bulk analysis of viral genomes retrieved directly from environmental samples. In this study, we performed a viral metagenomic analysis of five pools of mosquitoes belonging to Aedes, Anopheles and Culex species, collected from different pig farms in the vicinity of Shanghai, China, to explore the viral community carried by mosquitoes. The resulting metagenomic data revealed that viral community in the mosquitoes was highly diverse and varied in abundance among pig farms, which comprised of more than 48 viral taxonomic families, specific to vertebrates, invertebrates, plants, fungi, bacteria and protozoa. In addition, a considerable number of viral reads were related to viruses that are not classified by host. The read sequences related to animal viruses included parvoviruses, anelloviruses, circoviruses, flavivirus, rhabdovirus and seadornaviruses, which might be taken up by mosquitoes from viremic animal hosts during blood feeding. Notably, sample G1 contained the most abundant sequence related to Banna virus, which is of public health interest because it causes encephalitis in humans. Furthermore, non-classified viruses also shared considerable virus sequences in all the samples, presumably belonging to unexplored virus category. Overall, the present study provides a comprehensive knowledge of diverse viral populations carried by mosquitoes at pig farms, which is a potential source of diseases for mammals including humans and animals. These viral metagenomic data are valuable for assessment of emerging and re-emerging viral epidemics.

GloPID-R report on chikungunya, o'nyong-nyong and Mayaro virus, part 5: Entomological aspects.

The GloPID-R (Global Research Collaboration for Infectious Disease Preparedness) chikungunya (CHIKV), o'nyong-nyong (ONNV) and Mayaro virus (MAYV) Working Group has been established to investigate natural history, epidemiology and clinical aspects of infection by these viruses. Here, we present a report dedicated to entomological aspects of CHIKV, ONNV and MAYV. Recent global expansion of chikungunya virus has been possible because CHIKV established a transmission cycle in urban settings using anthropophilic vectors such as Aedes albopictus and Aedes aegypti. MAYV and ONNV have a more limited geographic distribution, being confined to Africa (ONNV) and central-southern America (MAYV). ONNV is probably maintained through an enzootic cycle that has not been characterized yet, with Anopheles species as main vectors and humans as amplification hosts during epidemics. MAYV is transmitted by Haemagogus species in an enzootic cycle using non-human primates as the main amplification and maintenance hosts, and humans becoming sporadically infected when venturing in or nearby forest habitats. Here, we focused on the transmission cycle and natural vectors that sustain circulation of these viruses in their respective locations. The knowledge of the natural ecology of transmission and the capacity of different vectors to transmit these viruses is crucial to understand CHIKV emergence, and to assess the risk that MAYV and ONNV will expand on wide scale using anthropophilic mosquito species not normally considered primary vectors. Finally, the experts identified knowledge gaps and provided adapted recommendations, in order to address future entomological investigations in the right direction.

Infected Mosquitoes Have Altered Behavior to Repellents: A Systematic Review and Meta-analysis.

Here we conducted a systematic review and meta-analysis to reach a consensus on whether infected and uninfected mosquitoes respond differently to repellents. After screening 2,316 published studies, theses, and conference abstracts, we identified 18 studies that tested whether infection status modulated the effectiveness of repellents. Thirteen of these studies had outcomes available for meta-analysis, and overall, seven repellents were tested (typically DEET with 62% of outcomes), six mosquito species had repellence behaviors measured (typically Aedes aegypti (L.) (Diptera: Culicidae) mosquitoes with 71% of outcomes), and a broad diversity of infections were tested including Sindbis virus (Togaviridae: Alphavirus) (33% of outcomes), Dengue (Flaviviridae: Flavivirus) (31%), malaria (Plasmodium berghei Vincke & Lips (Haemospororida: Plasmodiidae) or P. falciparum Welch (Haemospororida: Plasmodiidae); 25%), Zika (Flaviviridae: Flavivirus) (7%), and microsporidia (4%). Pooling all outcomes with meta-analysis, we found that repellents were less effective against infected mosquitoes-marking an average 62% reduction in protective efficacy relative to uninfected mosquitoes (pooled odds ratio = 0.38, 95% confidence interval = 0.22-0.66; k = 96). Older infected mosquitoes were also more likely to show altered responses and loss of sensitivity to repellents, emphasizing the challenge of distinguishing between age or incubation period effects. Plasmodium- or Dengue-infected mosquitoes also did not show altered responses to repellents; however, Dengue-mosquito systems used inoculation practices that can introduce variability in repellency responses. Given our findings that repellents offer less protection against infected mosquitoes and that these vectors are the most dangerous in terms of disease transmission, then trials on repellent effectiveness should incorporate infected mosquitoes to improve predictability in blocking vector-human contact.

Mosquitoes of North-Western Europe as Potential Vectors of Arboviruses: A Review.

BACKGROUND: The intensification of trade and travel is linked to the growing number of imported cases of dengue, chikungunya or Zika viruses into continental Europe and to the expansion of invasive mosquito species such as Aedes albopictus and Aedes japonicus. Local outbreaks have already occurred in several European countries. Very little information exists on the vector competence of native mosquitoes for arboviruses. As such, the vectorial status of the nine mosquito species largely established in North-Western Europe (Aedes cinereus and Aedes geminus, Aedes cantans, Aedes punctor, Aedes rusticus, Anopheles claviger s.s., Anopheles plumbeus, Coquillettidia richiardii, Culex pipiens s.l., and Culiseta annulata) remains mostly unknown. OBJECTIVES: To review the vector competence of both invasive and native mosquito populations found in North-Western Europe (i.e., France, Belgium, Germany, United Kingdom, Ireland, The Netherlands, Luxembourg and Switzerland) for dengue, chikungunya, Zika, West Nile and Usutu viruses. METHODS: A bibliographical search with research strings addressing mosquito vector competence for considered countries was performed. RESULTS: Out of 6357 results, 119 references were related to the vector competence of mosquitoes in Western Europe. Eight species appear to be competent for at least one virus. CONCLUSIONS: Aedes albopictus is responsible for the current outbreaks. The spread of Aedes albopictus and Aedes japonicus increases the risk of the autochthonous transmission of these viruses. Although native species could contribute to their transmission, more studies are still needed to assess that risk.

De novo profiling of RNA viruses in Anopheles malaria vector mosquitoes from forest ecological zones in Senegal and Cambodia.

BACKGROUND: Mosquitoes are colonized by a large but mostly uncharacterized natural virome of RNA viruses, and the composition and distribution of the natural RNA virome may influence the biology and immunity of Anopheles malaria vector populations. RESULTS: Anopheles mosquitoes were sampled in malaria endemic forest village sites in Senegal and Cambodia, including Anopheles funestus, Anopheles gambiae group sp., and Anopheles coustani in Senegal, and Anopheles hyrcanus group sp., Anopheles maculatus group sp., and Anopheles dirus in Cambodia. The most frequent mosquito species sampled at both study sites are human malaria vectors. Small and long RNA sequences were depleted of mosquito host sequences, de novo assembled and clustered to yield non-redundant contigs longer than 500 nucleotides. Analysis of the assemblies by sequence similarity to known virus families yielded 115 novel virus sequences, and evidence supports a functional status for at least 86 of the novel viral contigs. Important monophyletic virus clades in the Bunyavirales and Mononegavirales orders were found in these Anopheles from Africa and Asia. The remaining non-host RNA assemblies that were unclassified by sequence similarity to known viruses were clustered by small RNA profiles, and 39 high-quality independent contigs strongly matched a pattern of classic RNAi processing of viral replication intermediates, suggesting they are entirely undescribed viruses. One thousand five hundred sixty-six additional high-quality unclassified contigs matched a pattern consistent with Piwi-interacting RNAs (piRNAs), suggesting that strand-biased piRNAs are generated from the natural virome in Anopheles. To functionally query piRNA effect, we analyzed piRNA expression in Anopheles coluzzii after infection with O'nyong nyong virus (family Togaviridae), and identified two piRNAs that appear to display specifically altered abundance upon arbovirus infection. CONCLUSIONS: Anopheles vectors of human malaria in Africa and Asia are ubiquitously colonized by RNA viruses, some of which are monophyletic but clearly diverged from other arthropod viruses. The interplay between small RNA pathways, immunity, and the virome may represent part of the homeostatic mechanism maintaining virome members in a commensal or nonpathogenic state, and could potentially influence vector competence.