A systematic review and meta-analysis of the potential non-human animal reservoirs and arthropod vectors of the Mayaro virus.

Improving our understanding of Mayaro virus (MAYV) ecology is critical to guide surveillance and risk assessment. We conducted a PRISMA-adherent systematic review of the published and grey literature to identify potential arthropod vectors and non-human animal reservoirs of MAYV. We searched PubMed/MEDLINE, Embase, Web of Science, SciELO and grey-literature sources including PAHO databases and dissertation repositories. Studies were included if they assessed MAYV virological/immunological measured occurrence in field-caught, domestic, or sentinel animals or in field-caught arthropods. We conducted an animal seroprevalence meta-analysis using a random effects model. We compiled granular georeferenced maps of non-human MAYV occurrence and graded the quality of the studies using a customized framework. Overall, 57 studies were eligible out of 1523 screened, published between the years 1961 and 2020. Seventeen studies reported MAYV positivity in wild mammals, birds, or reptiles and five studies reported MAYV positivity in domestic animals. MAYV positivity was reported in 12 orders of wild-caught vertebrates, most frequently in the orders Charadriiformes and Primate. Sixteen studies detected MAYV in wild-caught mosquito genera including Haemagogus, Aedes, Culex, Psorophora, Coquillettidia, and Sabethes. Vertebrate animals or arthropods with MAYV were detected in Brazil, Panama, Peru, French Guiana, Colombia, Trinidad, Venezuela, Argentina, and Paraguay. Among non-human vertebrates, the Primate order had the highest pooled seroprevalence at 13.1% (95% CI: 4.3-25.1%). From the three most studied primate genera we found the highest seroprevalence was in Alouatta (32.2%, 95% CI: 0.0-79.2%), followed by Callithrix (17.8%, 95% CI: 8.6-28.5%), and Cebus/Sapajus (3.7%, 95% CI: 0.0-11.1%). We further found that MAYV occurs in a wide range of vectors beyond Haemagogus spp. The quality of evidence behind these findings was variable and prompts calls for standardization of reporting of arbovirus occurrence. These findings support further risk emergence prediction, guide field surveillance efforts, and prompt further in-vivo studies to better define the ecological drivers of MAYV maintenance and potential for emergence.

Genomic Epidemiology of Salmonid Alphavirus in Norwegian Aquaculture Reveals Recent Subtype-2 Transmission Dynamics and Novel Subtype-3 Lineages.

Viral disease poses a major barrier to sustainable aquaculture, with outbreaks causing large economic losses and growing concerns for fish welfare. Genomic epidemiology can support disease control by providing rapid inferences on viral evolution and disease transmission. In this study, genomic epidemiology was used to investigate salmonid alphavirus (SAV), the causative agent of pancreas disease (PD) in Atlantic salmon. Our aim was to reconstruct SAV subtype-2 (SAV2) diversity and transmission dynamics in recent Norwegian aquaculture, including the origin of SAV2 in regions where this subtype is not tolerated under current legislation. Using nanopore sequencing, we captured ~90% of the SAV2 genome for n = 68 field isolates from 10 aquaculture production regions sampled between 2018 and 2020. Using time-calibrated phylogenetics, we infer that, following its introduction to Norway around 2010, SAV2 split into two clades (SAV2a and 2b) around 2013. While co-present at the same sites near the boundary of Møre og Romsdal and Trøndelag, SAV2a and 2b were generally detected in non-overlapping locations at more Southern and Northern latitudes, respectively. We provide evidence for recent SAV2 transmission over large distances, revealing a strong connection between Møre og Romsdal and SAV2 detected in 2019/20 in Rogaland. We also demonstrate separate introductions of SAV2a and 2b outside the SAV2 zone in Sognefjorden (Vestland), connected to samples from Møre og Romsdal and Trøndelag, respectively, and a likely 100 km Northward transmission of SAV2b within Trøndelag. Finally, we recovered genomes of SAV2a and SAV3 co-infecting single fish in Rogaland, involving novel SAV3 lineages that diverged from previously characterized strains >25 years ago. Overall, this study demonstrates useful applications of genomic epidemiology for tracking viral disease spread in aquaculture.

Evaluation of Antiviral Activity of Cyclic Ketones against Mayaro Virus.

Mayaro virus (MAYV) is a neglected arthropod-borne virus found in the Americas. MAYV infection results in Mayaro fever, a non-lethal debilitating disease characterized by a strong inflammatory response affecting the joints and muscles. MAYV was once considered endemic to forested areas in Brazil but has managed to adapt and spread to urban regions using new vectors, such as Aedes aegypti, and has the potential to cause serious epidemics in the future. Currently, there are no vaccines or specific treatments against MAYV. In this study, the antiviral activity of a series of synthetic cyclic ketones were evaluated for the first time against MAYV. Twenty-four compounds were screened in a cell viability assay, and eight were selected for further evaluation. Effective concentration (EC50) and selectivity index (SI) were calculated and compound 9-(5-(4-chlorophenyl]furan-2-yl)-3,6-dimethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2))-dione (9) (EC50 = 21.5 µmol·L-1, SI = 15.8) was selected for mechanism of action assays. The substance was able to reduce viral activity by approximately 70% in both pre-treatment and post-treatment assays.

Ultrastructural insights into the replication cycle of salmon pancreas disease virus (SPDV) using salmon cardiac primary cultures (SCPCs).

Salmon pancreas disease virus (SPDV) has been affecting the salmon farming industry for over 30 years, but despite the substantial amount of studies, there are still a number of recognized knowledge gaps, for example in the transmission of the virus. In this work, an ultrastructural morphological approach was used to describe observations after infection by SPDV of an ex vivo cardiac model generated from Atlantic salmon embryos. The observations in this study and those available on previous ultrastructural work on SPDV are compared and contrasted with the current knowledge on terrestrial mammalian and insect alphaviral replication cycles, which is deeper than that of SPDV both morphologically and mechanistically. Despite their limitations, morphological descriptions remain an excellent way to generate novel hypotheses, and this has been the aim of this work. This study has used a target host, ex vivo model and resulted in some previously undescribed features, including filopodial membrane projections, cytoplasmic stress granules or putative intracytoplasmic budding. The latter suggests a new hypothesis that warrants further mechanistic research: SPDV in salmon may have retained the capacity for non-cytolytic (persistent) infections by intracellular budding, similar to that noted in arthropod vectors of other alphaviruses. In the notable absence of a known intermediate host for SPDV, the presence of this pattern suggests that both cytopathic and persistent infections may coexist in the same host. It is our hope that the ultrastructural comparison presented here stimulates new research that brings the knowledge on SPDV replication cycle up to a similar level to that of terrestrial alphaviruses.

Physiology and ecology combine to determine host and vector importance for Ross River virus.

Identifying the key vector and host species that drive the transmission of zoonotic pathogens is notoriously difficult but critical for disease control. We present a nested approach for quantifying the importance of host and vectors that integrates species' physiological competence with their ecological traits. We apply this framework to a medically important arbovirus, Ross River virus (RRV), in Brisbane, Australia. We find that vertebrate hosts with high physiological competence are not the most important for community transmission; interactions between hosts and vectors largely underpin the importance of host species. For vectors, physiological competence is highly important. Our results identify primary and secondary vectors of RRV and suggest two potential transmission cycles in Brisbane: an enzootic cycle involving birds and an urban cycle involving humans. The framework accounts for uncertainty from each fitted statistical model in estimates of species' contributions to transmission and has has direct application to other zoonotic pathogens.

Performance assessment of a multi-epitope chimeric antigen for the serological diagnosis of acute Mayaro fever.

Mayaro virus (MAYV), which causes mayaro fever, is endemic to limited regions of South America that may expand due to the possible involvement of Aedes spp. mosquitoes in its transmission. Its effective control will require the accurate identification of infected individuals, which has been restricted to nucleic acid-based tests due to similarities with other emerging members of the Alphavirus genus of the Togaviridae family; both in structure and clinical symptoms. Serological tests have a more significant potential to expand testing at a reasonable cost, and their performance primarily reflects that of the antigen utilized to capture pathogen-specific antibodies. Here, we describe the assembly of a synthetic gene encoding multiple copies of antigenic determinants mapped from the nsP1, nsP2, E1, and E2 proteins of MAYV that readily expressed as a stable chimeric protein in bacteria. Its serological performance as the target in ELISAs revealed a high accuracy for detecting anti-MAYV IgM antibodies. No cross-reactivity was observed with serum from seropositive individuals for dengue, chikungunya, yellow fever, Zika, and other infectious diseases as well as healthy individuals. Our data suggest that this bioengineered antigen could be used to develop high-performance serological tests for MAYV infections.

Impact of COVID-19 Mitigation Measures on Mosquito-Borne Diseases in 2020 in Queensland, Australia.

We describe the impact of COVID-19 mitigation measures on mosquito-borne diseases in Queensland, Australia, during the first half of 2020. Implementation of restrictions coincided with an atypical late season outbreak of Ross River virus (RRV) characterized by a peak in notifications in April (1173) and May (955) which were greater than 3-fold the mean observed for the previous four years. We propose that limitations on human movement likely resulted in the majority of RRV infections being acquired at or near the place of residence, and that an increase in outdoor activities, such as gardening and bushwalking in the local household vicinity, increased risk of exposure to RRV-infected mosquitoes. In contrast, the precipitous decline in international passenger flights led to a reduction in the number of imported dengue and malaria cases of over 70% and 60%, respectively, compared with the previous five years. This substantial reduction in flights also reduced a risk pathway for importation of exotic mosquitoes, but the risk posed by importation via sea cargo was not affected. Overall, the emergence of COVID-19 has had a varied impact on mosquito-borne disease epidemiology in Queensland, but the need for mosquito surveillance and control, together with encouragement of personal protective measures, remains unchanged.

Optimising predictive modelling of Ross River virus using meteorological variables.

BACKGROUND: Statistical models are regularly used in the forecasting and surveillance of infectious diseases to guide public health. Variable selection assists in determining factors associated with disease transmission, however, often overlooked in this process is the evaluation and suitability of the statistical model used in forecasting disease transmission and outbreaks. Here we aim to evaluate several modelling methods to optimise predictive modelling of Ross River virus (RRV) disease notifications and outbreaks in epidemiological important regions of Victoria and Western Australia. METHODOLOGY/PRINCIPAL FINDINGS: We developed several statistical methods using meteorological and RRV surveillance data from July 2000 until June 2018 in Victoria and from July 1991 until June 2018 in Western Australia. Models were developed for 11 Local Government Areas (LGAs) in Victoria and seven LGAs in Western Australia. We found generalised additive models and generalised boosted regression models, and generalised additive models and negative binomial models to be the best fit models when predicting RRV outbreaks and notifications, respectively. No association was found with a model's ability to predict RRV notifications in LGAs with greater RRV activity, or for outbreak predictions to have a higher accuracy in LGAs with greater RRV notifications. Moreover, we assessed the use of factor analysis to generate independent variables used in predictive modelling. In the majority of LGAs, this method did not result in better model predictive performance. CONCLUSIONS/SIGNIFICANCE: We demonstrate that models which are developed and used for predicting disease notifications may not be suitable for predicting disease outbreaks, or vice versa. Furthermore, poor predictive performance in modelling disease transmissions may be the result of inappropriate model selection methods. Our findings provide approaches and methods to facilitate the selection of the best fit statistical model for predicting mosquito-borne disease notifications and outbreaks used for disease surveillance.

The environmental and ecological determinants of elevated Ross River Virus exposure in koalas residing in urban coastal landscapes.

Koala populations in many areas of Australia have declined sharply in response to habitat loss, disease and the effects of climate change. Koalas may face further morbidity from endemic mosquito-borne viruses, but the impact of such viruses is currently unknown. Few seroprevalence studies in the wild exist and little is known of the determinants of exposure. Here, we exploited a large, spatially and temporally explicit koala survey to define the intensity of Ross River Virus (RRV) exposure in koalas residing in urban coastal environments in southeast Queensland, Australia. We demonstrate that RRV exposure in koalas is much higher (> 80%) than reported in other sero-surveys and that exposure is uniform across the urban coastal landscape. Uniformity in exposure is related to the presence of the major RRV mosquito vector, Culex annulirostris, and similarities in animal movement, tree use, and age-dependent increases in exposure risk. Elevated exposure ultimately appears to result from the confinement of remaining coastal koala habitat to the edges of permanent wetlands unsuitable for urban development and which produce large numbers of competent mosquito vectors. The results further illustrate that koalas and other RRV-susceptible vertebrates may serve as useful sentinels of human urban exposure in endemic areas.

Impact of alphavirus 3'UTR plasticity on mosquito transmission.

Alphaviruses such as chikungunya and western equine encephalitis viruses are important human pathogens transmitted by mosquitoes that have recently caused large epidemic and epizootic outbreaks. The epidemic potential of alphaviruses is often related to enhanced mosquito transmission. Tissue barriers and antiviral responses impose bottlenecks to viral populations in mosquitoes. Substitutions in the envelope proteins and the presence of repeated sequence elements (RSEs) in the 3'UTR of epidemic viruses were proposed to be specifically associated to efficient replication in mosquito vectors. Here, we discuss the molecular mechanisms that originated RSEs, the evolutionary forces that shape the 3'UTR of alphaviruses, and the significance of RSEs for mosquito transmission. Finally, the presence of RSEs in the 3'UTR of viral genomes appears as evolutionary trait associated to mosquito adaptation and emerges as a common feature among viruses from the alphavirus and flavivirus genera.

Sindbis Virus Infection in Non-Blood-Fed Hibernating Culex pipiens Mosquitoes in Sweden.

A crucial, but unresolved question concerning mosquito-borne virus transmission is how these viruses can remain endemic in regions where the transmission is halted for long periods of time, due to mosquito inactivity in, e.g., winter. In northern Europe, Sindbis virus (SINV) (genus alphavirus, Togaviridae) is transmitted among birds by Culex mosquitoes during the summer, with occasional symptomatic infections occurring in humans. In winter 2018-19, we sampled hibernating Culex spp females in a SINV endemic region in Sweden and assessed them individually for SINV infection status, blood-feeding status, and species. The results showed that 35 out of the 767 collected mosquitoes were infected by SINV, i.e., an infection rate of 4.6%. The vast majority of the collected mosquitoes had not previously blood-fed (98.4%) and were of the species Cx. pipiens (99.5%). This is the first study of SINV overwintering, and it concludes that SINV can be commonly found in the hibernating Cx. pipiens population in an endemic region in Sweden, and that these mosquitoes become infected through other means besides blood-feeding. Further studies on mosquito ecology and viral interactions are needed to elucidate the mechanisms of the persistence of these viruses over winter.

First Record of Mosquito-Borne Kyzylagach Virus in Central Europe.

RNA of Kyzylagach virus (KYZV), a Sindbis-like mosquito-borne alphavirus from Western equine encephalitis virus complex, was detected in four pools (out of 221 pools examined), encompassing 10,784 female Culex modestus mosquitoes collected at a fishpond in south Moravia, Czech Republic, with a minimum infection rate of 0.04%. This alphavirus was never detected in Central Europe before.

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.

The Mayaro virus and its potential epidemiological consequences in Colombia: an exploratory biomathematics analysis.

BACKGROUND: Mayaro virus (Togaviridae) is an endemic arbovirus of the Americas with epidemiological similarities with the agents of other more prominent diseases such as dengue (Flaviviridae), Zika (Flaviviridae), and chikungunya (Togaviridae). It is naturally transmitted in a sylvatic/rural cycle by Haemagogus spp., but, potentially, it could be incorporated and transmitted in an urban cycle by Aedes aegypti, a vector widely disseminated in the Americas. METHODS: The Mayaro arbovirus dynamics was simulated mathematically in the colombian population in the eight biogeographical provinces, bearing in mind the vector's population movement between provinces through passive transport via truck cargo. The parameters involved in the virus epidemiological dynamics, as well as the vital rates of Ae. aegypti in each of the biogeographical provinces were obtained from the literature. These data were included in a meta-population model in differential equations, represented by a model structured by age for the dynamic population of Ae. aegypti combined with an epidemiological SEI/SEIR-type model. In addition, the model was incorporated with a term of migration to represent the connectivity between the biogeographical provinces. RESULTS: The vital rates and the development cycle of Ae. aegypti varied between provinces, having greater biological potential between 23 °C and 28 °C in provinces of Imerí, biogeographical Chocó, and Magdalena, with respect to the North-Andean Moorland (9.33-21.38 °C). Magdalena and Maracaibo had the highest flow of land cargo. The results of the simulations indicate that Magdalena, Imerí, and biogeographical Chocó would be the most affected regarding the number of cases of people infected by Mayaro virus over time. CONCLUSIONS: The temperature in each of the provinces influences the local population dynamics of Ae. aegypti and passive migration via transport of land cargo plays an important role on how the Mayaro virus would be disseminated in the human population. Once this arbovirus begins an urban cycle, the most-affected departments would be Antioquia, Santander, Norte de Santander, Cesar (Provinces of Magdalena), and Valle del Cauca, and Chocó (biogeographical province of Chocó), which is why vector control programmes must aim their efforts at these departments and include some type of vector control to the transport of land cargo to avoid a future Mayaro epidemic.

Spatial and temporal patterns of Ross River virus in south east Queensland, Australia: identification of hot spots at the rural-urban interface.

BACKGROUND: Ross River virus (RRV) is responsible for the most common vector-borne disease of humans reported in Australia. The virus circulates in enzootic cycles between multiple species of mosquitoes, wildlife reservoir hosts and humans. Public health concern about RRV is increasing due to rising incidence rates in Australian urban centres, along with increased circulation in Pacific Island countries. Australia experienced its largest recorded outbreak of 9544 cases in 2015, with the majority reported from south east Queensland (SEQ). This study examined potential links between disease patterns and transmission pathways of RRV. METHODS: The spatial and temporal distribution of notified RRV cases, and associated epidemiological features in SEQ, were analysed for the period 2001-2016. This included fine-scale analysis of disease patterns across the suburbs of the capital city of Brisbane, and those of 8 adjacent Local Government Areas, and host spot analyses to identify locations with significantly high incidence. RESULTS: The mean annual incidence rate for the region was 41/100,000 with a consistent seasonal peak in cases between February and May. The highest RRV incidence was in adults aged from 30 to 64 years (mean incidence rate: 59/100,000), and females had higher incidence rates than males (mean incidence rates: 44/100,000 and 34/100,000, respectively). Spatial patterns of disease were heterogeneous between years, and there was a wide distribution of disease across both urban and rural areas of SEQ. Overall, the highest incidence rates were reported from predominantly rural suburbs to the north of Brisbane City, with significant hot spots located in peri-urban suburbs where residential, agricultural and conserved natural land use types intersect. CONCLUSIONS: Although RRV is endemic across all of SEQ, transmission is most concentrated in areas where urban and peri-urban environments intersect. The drivers of RRV transmission across rural-urban landscapes should be prioritised for further investigation, including identification of specific vectors and hosts that mediate human spillover.

Epidemiological models for predicting Ross River virus in Australia: A systematic review.

Ross River virus (RRV) is the most common and widespread arbovirus in Australia. Epidemiological models of RRV increase understanding of RRV transmission and help provide early warning of outbreaks to reduce incidence. However, RRV predictive models have not been systematically reviewed, analysed, and compared. The hypothesis of this systematic review was that summarising the epidemiological models applied to predict RRV disease and analysing model performance could elucidate drivers of RRV incidence and transmission patterns. We performed a systematic literature search in PubMed, EMBASE, Web of Science, Cochrane Library, and Scopus for studies of RRV using population-based data, incorporating at least one epidemiological model and analysing the association between exposures and RRV disease. Forty-three articles, all of high or medium quality, were included. Twenty-two (51.2%) used generalised linear models and 11 (25.6%) used time-series models. Climate and weather data were used in 27 (62.8%) and mosquito abundance or related data were used in 14 (32.6%) articles as model covariates. A total of 140 models were included across the articles. Rainfall (69 models, 49.3%), temperature (66, 47.1%) and tide height (45, 32.1%) were the three most commonly used exposures. Ten (23.3%) studies published data related to model performance. This review summarises current knowledge of RRV modelling and reveals a research gap in comparing predictive methods. To improve predictive accuracy, new methods for forecasting, such as non-linear mixed models and machine learning approaches, warrant investigation.

A micro-PRNT for the detection of Ross River virus antibodies in mosquito blood meals: A useful tool for inferring transmission pathways.

INTRODUCTION: Many arboviruses of public health significance are maintained in zoonotic cycles with complex transmission pathways. The presence of serum antibody against arboviruses in vertebrates provides evidence of their historical exposure but reveals nothing about the vector-reservoir relationship. Moreover, collecting blood or tissue samples from vertebrate hosts is ethically and logistically challenging. We developed a novel approach for screening the immune status of vertebrates against Ross River virus that allows us to implicate the vectors that form the transmission pathways for this commonly notified Australian arboviral disease. METHODS: A micro-plaque reduction neutralisation test (micro-PRNT) was developed and validated on koala (Phascolarctos cinereus) sera against a standard PRNT. The ability of the micro-PRNT to detect RRV antibodies in mosquito blood meals was then tested using two mosquito models. Laboratory-reared Aedes aegypti were fed, via a membrane, on sheep blood supplemented with RRV seropositive and seronegative human sera. Aedes notoscriptus were fed on RRV seropositive and seronegative human volunteers. Blood-fed mosquitoes were harvested at various time points after feeding and their blood meals analysed for the presence of RRV neutralising antibodies using the micro-PRNT. RESULTS: There was significant agreement of the plaque neutralisation resulting from the micro-PRNT and standard PRNT techniques (R2 = 0.65; P<0.0001) when applied to RRV antibody detection in koala sera. Sensitivity and specificity of the micro-PRNT assay were 88.2% and 96%, respectively, in comparison with the standard PRNT. Blood meals from mosquitoes fed on sheep blood supplemented with RRV antibodies, and on blood from RRV seropositive humans neutralised the virus by ≥50% until 48 hr post feeding. The vertebrate origin of the blood meal was also ascertained for the same samples, in parallel, using established molecular techniques. CONCLUSIONS: The small volumes of blood present in mosquito abdomens can be used to identify RRV antibodies and therefore host exposure to arbovirus infection. In tandem with the accurate identification of the mosquito, and diagnostics for the host origin of the blood meal, this technique has tremendous potential for exploring RRV transmission pathways. It can be adapted for similar studies on other mosquito borne zoonoses.

Associations Between Ross River Virus Infection in Humans and Vector-Vertebrate Community Ecology in Brisbane, Australia.

Transmission of vector-borne pathogens can vary in complexity from single-vector, single-host systems through to multivector, multihost vertebrate systems. Understanding the dynamics of transmission is important for disease prevention efforts, but is dependent on disentangling complex interactions within coupled natural systems. Ross River virus (RRV) is a multivector multihost pathogen responsible for the greatest number of notified vector-borne pathogen infections in humans in Australia. Current evidence suggests that nonhuman vertebrates are critical for the maintenance and spillover of RRV into mosquito populations. Yet, there is a limited knowledge of which mosquito vector species and amplifying vertebrate host species are most important for transmission of RRV to humans. We conducted field surveys of nonhuman vertebrates and mosquitoes in the RRV endemic city of Brisbane, Australia, to assess the effect of vector and host community structure on human RRV notifications. Six suburbs were selected across a gradient of human disease notification rates. Differences in vertebrate and mosquito compositions were observed across all suburbs. Suburbs with higher RRV notification rates contained greater vertebrate biomass (dominated by the presence of horses) and higher mosquito abundances. This study suggests that horse-mosquito interactions should be considered in more detail and that vertebrate biomass and mosquito abundance be incorporated into future RRV modeling studies and considered in public health strategies for RRV management.

Vector competence of Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus mosquitoes for Mayaro virus.

Newly emerging or re-emerging arthropod-borne viruses (arboviruses) are important causes of human morbidity and mortality worldwide. Arboviruses such as Dengue (DENV), Zika (ZIKV), Chikungunya (CHIKV), and West Nile virus (WNV) have undergone extensive geographic expansion in the tropical and sub-tropical regions of the world. In the Americas the main vectors of DENV, ZIKV, and CHIKV are mosquito species adapted to urban environments, namely Aedes aegypti and Aedes albopictus, whereas the main vector of WNV is Culex quinquefasciatus. Given the widespread distribution in the Americas and high permissiveness to arbovirus infection, these mosquito species may play a key role in the epidemiology of other arboviruses normally associated with sylvatic vectors. Here, we test this hypothesis by determining the vector competence of Ae. aegypti, Ae. albopictus, and Cx. quinquefasciatus to Mayaro (MAYV) virus, a sylvatic arbovirus transmitted mainly by Haemagogus janthinomys that has been causing an increasing number of outbreaks in South America, namely in Brazil. Using field mosquitoes from Brazil, female mosquitoes were experimentally infected, and their competence for infection and transmission rates of MAYV was evaluated. We found consistent infection rate for MAYV in Ae. aegypti (57.5%) and Ae. albopictus (61.6%), whereas very low rates were obtained for Cx. quinquefasciatus (2.5%). Concordantly, we observed high potential transmission ability in Ae. aegypti and Ae. albopictus (69.5% and 71.1% respectively), in contrast to Cx. quinquefasciatus, which could not transmit the MAYV. Notably, we found that very low quantities of virus present in the saliva (undetectable by RT-qPCR) were sufficiently virulent to guarantee transmission. Although Ae. aegypti and Ae. albopictus mosquitoes are not the main vectors for MAYV, our studies suggest that these mosquitoes could play a significant role in the transmission of this arbovirus, since both species showed significant vector competence for MAYV (Genotype D), under laboratory conditions.