Mycobacterium tuberculosis complex in domestic goats in Southern Spain.

Tuberculosis (TB) is a zoonotic infectious disease caused by bacteria belonging to the Mycobacterium tuberculosis complex (MTC), which can affect a wide variety of domestic and wild animal species. Although the role of goats as a reservoir of MTC bacteria has been evidenced, information about the circulation of MTC strains in this species is still very scarce. The aim of the present study was to determine the seroprevalence, spatial distribution, risk factors and MTC spoligotypes circulating in goats from Andalusia (Southern Spain), the Spanish region with the largest goat census and a hotspot area of TB in both cattle and wild ungulates. A total of 2155 serum samples from 80 goat flocks were analyzed by an in-house ELISA using the P22 protein complex as a coating antigen. Antibodies against MTC were detected in 473 goats (21.9%, 95% CI: 20.2-23.7) and the true seroprevalence was 22.3% (95% CI: 20.6-24.1). Seropositivity was found in 72 (90.0%) of the 80 flocks analyzed. The generalized estimating equation model showed that the management system (higher seroprevalence on intensive and semi-intensive farms), and the presence of hospital pens inside the regular stables, were risk factors potentially associated with MTC exposure in goats in Southern Spain. The spatial analysis identified a significant spatial cluster (p < 0.001) in Eastern Andalusia. A total of 16 different MTC spoligotypes, including five of M. caprae and eleven of M. bovis, were identified in goats between 2015 and 2022 in the study area, with SB0157 as the most frequently isolated. The results obtained indicate widespread and non-homogeneous spatial distribution of MTC in goat herds from Southern Spain. The high individual and herd-level seroprevalence values found suggest that goats could play a significant role in the maintenance and transmission of MTC in the study area. Our results highlight the importance of implementing control measures in this species.

Dynamics of Crimean-Congo hemorrhagic fever virus in two wild ungulate hosts during a disease-induced population collapse.

Identifying the role that host species play in pathogen transmission and maintenance is crucial for disease control, but it is a difficult task, in particular for vector-borne and multi-host pathogens, and especially when wildlife species are involved. This is the case for a Crimean-Congo hemorrhagic fever virus (CCHFV) hotspot in north-eastern Spain, where Iberian ibex (Capra pyrenaica) and wild boar (Sus scrofa) are involved, but their roles in disease transmission are unclear. In this context, we studied the dynamics of CCHFV transmission in these two species during the collapse of an Iberian ibex population due to a sarcoptic mange outbreak. We carried out a repeated cross-sectional study measuring the trends of CCHFV seroprevalence in Iberian ibex and wild boar and their abundances. In addition, we identified the tick species present in this area on the vegetation and on wild boars, and evaluated relevant meteorological factors. Results show that while the trends in CCHFV seroprevalence in Iberian Ibex and density of wild boars remained constant (p = 1.0 and p = 0.8, respectively), both the trends in Iberian ibex census and CCHFV seroprevalence in wild boars decreased significantly (p = 0.003 and p = 0.0001, respectively), and were correlated (Spearman's rank, 0.02 < p-adjusted<0.05). The correlation between the patterns of reduction of Iberian ibex abundance and the decrease of seroprevalence in wild boars suggests some sort of shared transmission cycle between the two species. Data from tick species in the area suggest a possible role of Rhipicephalus bursa in CCHFV transmission. The dynamics of CCHFV were unlikely caused by changes in meteorological variables such as temperature or water vapor pressure deficit. Further studies will be needed to confirm these hypotheses.

Crimean-Congo Hemorrhagic Fever Virus Seropositivity among Dromedary Camels, Algeria, 2020-2021.

Serosurvey results for Crimean-Congo hemorrhagic fever virus antibodies in dromedary camels in Algeria indicate that the pathogen is circulating endemically in desertic areas, despite the hostile environment. Thus, dromedaries are suitable sentinels for detecting human risk for Crimean-Congo hemorrhagic fever in desertic areas.

Risk factors associated with Streptococcus suis cases on pig farms in Spain.

BACKGROUND: Streptococcus suis can cause meningitis, polyarthritis and acute death in piglets. However, the risk factors associated with S. suis infection remain incompletely understood. Therefore, a longitudinal study was carried out, in which six batches from two Spanish pig farms with S. suis problems were repeatedly examined to determine possible risk factors. METHODS: A prospective case-control study was conducted, and potential risk factors were evaluated using mixed-effects logistic regression models. The explanatory variables included: (a) concomitant pathogens; (b) biomarkers associated with stress, inflammation and oxidative status; (c) farm environmental factors; and (d) parity and S. suis presence in sows. Three models were built to study the effect of these variables, including two to assess the risk factors involved in the subsequent development of disease. RESULTS: Risk factors for S. suis-associated disease included porcine reproductive and respiratory syndrome virus co-infection at weaning (odds ratio [OR] = 6.69), sow parity (OR = 0.71), haptoglobin level before weaning (OR = 1.01), relative humidity (OR = 1.11) and temperature (OR = 0.13). LIMITATIONS: Laboratory diagnosis was done at the batch level, with individual diagnosis based on clinical signs only. CONCLUSIONS: This study confirms the multifactorial nature of S. suis-associated disease, with both environmental factors and factors related to the host involved in disease development. Controlling these factors may, therefore, help prevent the appearance of disease.

Seroepidemiology of tuberculosis in sheep in southern Spain.

Tuberculosis (TB) is a multi-host infectious disease caused by members of the Mycobacterium tuberculosis complex (MTC). In Mediterranean ecosystems, where multiple animal hosts of TB are present, identifying the role of the different species involved in the epidemiology of TB is a key point to be able to implement proper control measures. Sheep are susceptible to MTC infection but have traditionally been considered a spillover host. However, the occurrence of outbreaks involving sheep in recent years evidences the need to better understand the role of this small ruminant species in the epidemiology of the disease. Here, we aimed to determine the seroprevalence and risk factors associated with MTC seropositivity in sheep in Andalusia (southern Spain), a region with one of the highest prevalence of MTC infection in both cattle and wild ungulates. A total of 2266 sheep from 83 flocks were tested for antibodies against MTC using an in-house indirect ELISA. Anti-MTC antibodies were detected in 16 (0.7%) of the 2266 sheep (adjusted true prevalence 0.29%, 95% posterior probability interval 0.01-1.05). Seropositivity was found in 14.5% (12/83; 95%CI: 6.9-22.0) of the sheep farms analyzed. A semi-extensive management system was identified as a risk factor associated with MTC seropositivity in sheep farms (OR = 3.7; p < 0.038; 95%CI: 1.1-12.4) in the study area. To the best of the authors' knowledge, this is the first active TB surveillance study carried out to assess MTC exposure in sheep. Our results indicate MTC circulation in sheep farms in southern Spain. However, the low individual seroprevalence obtained suggests that sheep may play a limited role in the epidemiology of TB in this region. Serosurveillance programs could be a valuable tool to detect MTC circulation in sheep in risk scenarios or target farms, in order to optimize control measures on TB animal in multi-host Mediterranean ecosystems.

Lack of Detection of Toxoplasma gondii in Pipistrellus spp. Bats from Densely Cat-Populated Areas of NE Spain.

Toxoplasma gondii infection in healthy animals is often asymptomatic. However, some species with little history of contact with the parasite, such as marsupials and New World primates, present high mortality rates after infection. Despite its potential conservation concern, T. gondii infection in insectivorous bats has received little attention, and its impact on bat populations' health is unknown. To assess the putative role of insectivorous bats in the cycle of T. gondii, samples of three species of bats (Pipistrellus pipistrellus, P. pygmaeus and P. kuhlii) collected between 2019 and 2021 in NE Spain were tested for the presence of the parasite using a qPCR. All tissues resulted negative (0.0% prevalence with 95% CI: [0.0-2.6]) for the presence of T. gondii. Unlike previous studies on insectivorous bats from Europe, Asia and America, the present study suggests that Pipistrellus spp. bats do not play a significant role in the epidemiology of T. gondii in NE Spain. Further studies are encouraged to elucidate both the epidemiology of T. gondii and its potential impact on the health of microchiropteran species in Europe.

Agreement and differential use of laboratory methods for the detection and quantification of SARS-CoV-2 in experimentally infected animals.

Rodents are widely used for the development of COVID-19-like animal models, the virological outcome being determined through several laboratory methods reported in the literature. Our objective was to assess the agreement between methods performed on different sample types from 342 rodents experimentally infected with SARS-CoV-2 (289 golden Syrian hamsters and 53 K18-hACE2 mice). Our results showed moderate agreement between methods detecting active viral replication, and that increasing viral loads determined by either RT-qPCR or infectious viral titration corresponded to increasing immunohistochemical scores. The percentage of agreement between methods decreased over experimental time points, and we observed poor agreement between RT-qPCR results and viral titration from oropharyngeal swabs. In conclusion, RT-qPCR and viral titration on tissue homogenates are the most reliable techniques to determine the presence and replication of SARS-CoV-2 in the early and peak phases of infection, and immunohistochemistry is valuable to evaluate viral distribution patterns in the infected tissues.

Evidence of Prolonged Crimean-Congo Hemorrhagic Fever Virus Endemicity by Retrospective Serosurvey, Eastern Spain.

We conducted a retrospective serosurvey for antibodies against Crimean-Congo hemorrhagic fever virus in wild ungulates along the eastern Mediterranean Coast of Spain. The virus has been endemic in this region since 2010 but is mainly restricted to geographic clusters with extremely high seropositivity associated with high density of bovids.

West Nile Virus Lineage 2 Spreads Westwards in Europe and Overwinters in North-Eastern Spain (2017-2020).

West Nile virus lineage 2 (WNV-L2) emerged in Europe in 2004; since then, it has spread across the continent, causing outbreaks in humans and animals. During 2017 and 2020, WNV-L2 was detected and isolated from four northern goshawks in two provinces of Catalonia (north-eastern Spain). In order to characterise the first Spanish WNV-L2 isolates and elucidate the potential overwintering of the virus in this Mediterranean region, complete genome sequencing, phylogenetic analyses, and a study of phenotypic characterisation were performed. Our results showed that these Spanish isolates belonged to the central-southern WNV-L2 clade. In more detail, they were related to the Lombardy cluster that emerged in Italy in 2013 and has been able to spread westwards, causing outbreaks in France (2018) and Spain (2017 and 2020). Phenotypic characterisation performed in vitro showed that these isolates presented characteristics corresponding to strains of moderate to high virulence. All these findings evidence that these WNV-L2 strains have been able to circulate and overwinter in the region, and are pathogenic, at least in northern goshawks, which seem to be very susceptible to WNV infection and may be good indicators of WNV-L2 circulation. Due to the increasing number of human and animal cases in Europe in the last years, this zoonotic flavivirus should be kept under extensive surveillance, following a One-Health approach.

Trends in the interest in COVID-19 news of the local media and their readers: The case of Spain.

The COVID-19 has caused not just an unprecedented sanitary crisis but a social crisis, which has affected, among many other fields, the local journalism, which had to adapt to meet the public's information needs about coronavirus. In this study we analyzed the evolution of local news about COVID-19 in Spain throughout the pandemic by examining local news articles in social media. Using a unique dataset of over 230k Facebook posts published by Spanish local media organizations during 2020 and 2021, we found evidence that the interest of local media in COVID-19, measured as the proportion of the news related to COVID-19, changed as the pandemic evolved. Our results also show that the interest that local media readers had in COVID-19, measured as the proportion Facebook interactions related to COVID-19, was even higher, and also evolved during the pandemic. Although the interest in COVID-19 of local media and their readers essentially progressed in parallel, we also identified some periods in which they behaved differently. While a fatigue with COVID-19 related news would be expected after 2 years of pandemic, a clear decrease of interest was not observed neither in journalists nor in readers.

Widespread Circulation of Flaviviruses in Horses and Birds in Northeastern Spain (Catalonia) between 2010 and 2019.

The surveillance for West Nile virus (WNV) in Catalonia (northeastern Spain) has consistently detected flaviviruses not identified as WNV. With the aim of characterizing the flaviviruses circulating in Catalonia, serum samples from birds and horses collected between 2010 and 2019 and positive by panflavivirus competition ELISA (cELISA) were analyzed by microneutralization test (MNT) against different flaviviruses. A third of the samples tested were inconclusive by MNT, highlighting the limitations of current diagnostic techniques. Our results evidenced the widespread circulation of flaviviruses, in particular WNV, but also Usutu virus (USUV), and suggest that chicken and horses could serve as sentinels for both viruses. In several regions, WNV and USUV overlapped, but no significant geographical aggregation was observed. Bagaza virus (BAGV) was not detected in birds, while positivity to tick-borne encephalitis virus (TBEV) was sporadically detected in horses although no endemic foci were observed. So far, no human infections by WNV, USUV, or TBEV have been reported in Catalonia. However, these zoonotic flaviviruses need to be kept under surveillance, ideally within a One Health framework.

Stochastic Assessment of the Economic Impact of Streptococcus suis-Associated Disease in German, Dutch and Spanish Swine Farms.

The economic assessment of animal diseases is essential for decision-making, including the allocation of resources for disease control. However, that assessment is usually hampered by the lack of reliable data on disease incidence, or treatment and control measures, and that is particularly true for swine production diseases, such as infections caused by Streptococcus suis. Therefore, we deployed a questionnaire survey of clinical swine veterinarians to obtain the input data needed for a stochastic model to calculate the costs caused by S. suis, which was implemented in three of the main swine producing countries in Europe: Germany, the Netherlands and Spain. S. suis-associated disease is endemic in those countries in all production phases, though nursery was the phase most severely impacted. In affected nursery units, between 3.3 and 4.0% of pigs had S. suis-associated disease and the mortalities ranged from 0.5 to 0.9%. In Germany, the average cost of S. suis per pig (summed across all production phases) was 1.30 euros (90% CI: 0.53-2.28), in the Netherlands 0.96 euros (90% CI: 0.27-1.54), and in Spain 0.60 euros (90% CI: 0.29-0.96). In Germany, that cost was essentially influenced by the expenditure in early metaphylaxis in nursery and in autogenous vaccines in sows and nursery pigs; in the Netherlands, by expenditure on autogenous vaccines in sows and nursery pigs; and in Spain, by the expenditures in early metaphylaxis and to a lesser extent by the mortality in nursery pigs. Therefore, the differences in costs between countries can be explained to a great extent by the measures to control S. suis implemented in each country. In Spain and in Germany, use of antimicrobials, predominantly beta-lactams, is still crucial for the control of the disease.

Hotspot of Crimean-Congo Hemorrhagic Fever Virus Seropositivity in Wildlife, Northeastern Spain.

We conducted a serosurvey for Crimean-Congo hemorrhagic fever virus antibodies in various wildlife species in Catalonia, northeastern Spain. We detected high seroprevalence in southern Catalonia, close to the Ebro Delta wetland, a key stopover for birds migrating from Africa. Our findings could indicate that competent virus vectors are present in the region.

Transmission of Similar Mcr-1 Carrying Plasmids among Different Escherichia coli Lineages Isolated from Livestock and the Farmer.

Colistin use has mostly been stopped in human medicine, due to its toxicity. However, nowadays, it still is used as a last-resort antibiotic to treat hospital infections caused by multi-drug resistant Enterobacteriaceae. On the contrary, colistin has been used in veterinary medicine until recently. In this study, 210 fecal samples from pigs (n = 57), calves (n = 152), and the farmer (n = 1) were collected from a farm where E. coli harboring mcr-1-mcr-3 was previously detected. Samples were plated, and mcr-genes presence was confirmed by multiplex-PCR. Hybrid sequencing which determined the presence and location of mcr-1, other antibiotic resistance genes, and virulence factors. Eighteen colistin resistant isolates (13 from calves, four from pigs, and one from the farmer) contained mcr-1 associated with plasmids (IncX4, IncI2, and IncHI2), except for two that yielded mcr-1 in the chromosome. Similar plasmids were distributed in different E. coli lineages. Transmission of mcr-1 to the farmer most likely occurred by horizontal gene transfer from E. coli of calf origin, since plasmids were highly similar (99% coverage, 99.97% identity). Moreover, 33 virulence factors, including stx2 for Shiga toxin E. coli (STEC) were detected, highlighting the role of livestock as a reservoir of pathotypes with zoonotic potential.

Feed additives for the control of post-weaning Streptococcus suis disease and the effect on the faecal and nasal microbiota.

Medicated feed is a common strategy to control the occurrence of Streptococcus suis disease in swine production, but feed additives may constitute an alternative to metaphylaxis. In a farm with post-weaning S. suis disease, the following additives were tested: lysozyme (Lys), medium chain fatty acids plus lysozyme (FA + Lys), FA plus a natural anti-inflammatory (FA + antiinf) and amoxicillin (Amox). During the course of the study, FA + antiinf and Amox groups showed lower prevalence of clinical signs compatible with S. suis disease than the rest of the groups. Piglets from the FA + antiinf group showed high diversity and richness in their nasal and faecal microbiota. Diet supplements did not have major effects on the faecal microbiota, where the genus Mitsuokella was the only differentially present in the FA + Lys group. In the nasal microbiota, piglets from FA + antiinf presented higher differential abundance of a sequence variant from Ruminococcaceae and lower abundance of an unclassified genus from Weeksellaceae. In general, we detected more significant changes in the nasal than in the feacal microbiota, and found that parity of the dams affected the microbiota composition of their offspring, with piglets born to gilts exhibiting lower richness and diversity. Our results suggest that additives could be useful to control post-weaning disease when removing antimicrobials in farms.

The Role of Birds of Prey in West Nile Virus Epidemiology.

Reported human cases of West Nile virus (WNV) in Europe increased dramatically in 2018. Lineage 1 strains had been circulating in Euro-Mediterranean countries since the early 1990s. The subsequent introduction of WNV lineage 2 has been responsible for the remarkable upsurge of European WNV outbreaks since 2004, including the dramatic increase in human cases observed since 2018. The virus exists in a natural cycle between mosquitoes and wild birds, with humans and horses acting as dead-end hosts. As the key vertebrate hosts in the transmission cycle of WNV, avian species have been the focus of surveillance across many countries. Raptors appear particularly susceptible to WNV infection, resulting in higher prevalence, and in some cases exhibiting neurological signs that lead to the death of the animal. In addition, birds of prey are known to play an important role as WNV reservoir and potentially amplifying hosts of infection. Importantly, raptor higher susceptibility/prevalence may indicate infection through predation of infected prey. Consequently, they are considered important target species when designing cost-effective surveillance for monitoring both seasonal WNV circulation in endemic countries and its emergence into new areas, where migrating raptors may play a critical role in virus introduction. This review summarizes the different aspects of the current knowledge of WNV infection in birds of prey and evaluates their role in the evolution of the epizootic that is spreading throughout Europe.

Cross-Validation of Generic Risk Assessment Tools for Animal Disease Incursion Based on a Case Study for African Swine Fever.

In recent years, several generic risk assessment (RA) tools have been developed that can be applied to assess the incursion risk of multiple infectious animal diseases allowing for a rapid response to a variety of newly emerging or re-emerging diseases. Although these tools were originally developed for different purposes, they can be used to answer similar or even identical risk questions. To explore the opportunities for cross-validation, seven generic RA tools were used to assess the incursion risk of African swine fever (ASF) to the Netherlands and Finland for the 2017 situation and for two hypothetical scenarios in which ASF cases were reported in wild boar and/or domestic pigs in Germany. The generic tools ranged from qualitative risk assessment tools to stochastic spatial risk models but were all parameterized using the same global databases for disease occurrence and trade in live animals and animal products. A comparison of absolute results was not possible, because output parameters represented different endpoints, varied from qualitative probability levels to quantitative numbers, and were expressed in different units. Therefore, relative risks across countries and scenarios were calculated for each tool, for the three pathways most in common (trade in live animals, trade in animal products, and wild boar movements) and compared. For the 2017 situation, all tools evaluated the risk to the Netherlands to be higher than Finland for the live animal trade pathway, the risk to Finland the same or higher as the Netherlands for the wild boar pathway, while the tools were inconclusive on the animal products pathway. All tools agreed that the hypothetical presence of ASF in Germany increased the risk to the Netherlands, but not to Finland. The ultimate aim of generic RA tools is to provide risk-based evidence to support risk managers in making informed decisions to mitigate the incursion risk of infectious animal diseases. The case study illustrated that conclusions on the ASF risk were similar across the generic RA tools, despite differences observed in calculated risks. Hence, it was concluded that the cross-validation contributed to the credibility of their results.

Near Real-Time Monitoring of Clinical Events Detected in Swine Herds in Northeastern Spain.

Novel techniques of data mining and time series analyses allow the development of new methods to analyze information relating to the health status of the swine population in near real-time. A swine health monitoring system based on the reporting of clinical events detected at farm level has been in operation in Northeastern Spain since 2012. This initiative was supported by swine stakeholders and veterinary practitioners of the Catalonia, Aragon, and Navarra regions. The system aims to evidence the occurrence of endemic diseases in near real-time by gathering data from practitioners that visited swine farms in these regions. Practitioners volunteered to report data on clinical events detected during their visits using a web application. The system allowed collection, transfer and storage of data on different clinical signs, analysis, and modeling of the diverse clinical events detected, and provision of reproducible reports with updated results. The information enables the industry to quantify the occurrence of endemic diseases on swine farms, better recognize their spatiotemporal distribution, determine factors that influence their presence and take more efficient prevention and control measures at region, county, and farm level. This study assesses the functionality of this monitoring tool by evaluating the target population coverage, the spatiotemporal patterns of clinical signs and presumptive diagnoses reported by practitioners over more than 6 years, and describes the information provided by this system in near real-time. Between January 2012 and March 2018, the system achieved a coverage of 33 of the 62 existing counties in the three study regions. Twenty-five percent of the target swine population farms reported one or more clinical events to the system. During the study period 10,654 clinical events comprising 14,971 clinical signs from 1,693 farms were reported. The most frequent clinical signs detected in these farms were respiratory, followed by digestive, neurological, locomotor, reproductive, and dermatological signs. Respiratory disorders were mainly associated with microorganisms of the porcine respiratory disease complex. Digestive signs were mainly related to colibacilosis and clostridiosis, neurological signs to Glässer's disease and streptococcosis, reproductive signs to PRRS, locomotor to streptococcosis and Glässer's disease, and dermatological signs to exudative epidermitis.

Evaluation of the effectiveness of the surveillance system for tuberculosis in cattle in Spain.

In Spain, the eradication of tuberculosis (TB) in cattle has had some setbacks and therefore we need to re-evaluate the current surveillance strategies. The Spanish cattle TB surveillance system consists of three components: a) routine skin testing, b) slaughterhouse surveillance, and c) pre-movement controls. Our objectives were to assess the effectiveness of the whole surveillance system and evaluate the relative contribution of each of those components, both at national and at the province level. The effectiveness was estimated based on both the sensitivity of detection per year and the time until detection. Moreover, we evaluated the impact of different factors on that effectiveness. We used a stochastic model that simulated the spread of Mycobacterium tuberculosis-complex (MTC) infection within cattle herds that was modified to incorporate the three components of TB surveillance. Input data, at the province level, on cattle movements off-farm or the frequency of the routine screening were provided by the Spanish Ministry for Agriculture, Fisheries and Food. Under the current conditions, 96.1% of Spanish herds were detected within one year after their infection (i.e. mean sensitivity of TB surveillance), although that detection took on average 178 days. The surveillance system effectiveness was highly dependent on the routine skin testing, responsible for the detection of almost 90% of the infected herds, while slaughterhouse surveillance and pre-movement controls contributed only to the identification of a small proportion of infected herds. We observed substantial differences in the effectiveness of the surveillance components among Spanish provinces, although in general, the sensitivities were high. The most influential factor on the efficiency of TB detection in Spain was, by far, the frequency of routine controls, followed by the sensitivity of the test used. In a context of reduced funding for cattle TB eradication, the frequency of testing should be adapted based on risk-based surveillance strategies, i.e. efforts should focus on herds more likely to be infected, but also in herds more likely to infect other herds. While slaughterhouse surveillance seems a cost-effective strategy, the use of pre-movement testing at least in areas of low incidence should be further evaluated.

Field-captured Aedes vexans (Meigen, 1830) is a competent vector for Rift Valley fever phlebovirus in Europe.

BACKGROUND: Aedes vexans (Meigen) is considered a nuisance species in central Europe and the Mediterranean region. It is an anthropophilic and mammalophilic floodwater mosquito involved in the transmission of several arboviruses. Rift Valley fever (RVF) is a relevant mosquito-borne zoonosis, affecting mainly humans and ruminants, that causes severe impact in public health and economic loses. Due to globalization and climate change, the European continent is threatened by its introduction. The main purpose of the present study was to evaluate the vector competence of a European field-collected Ae. vexans population. METHODS: Aedes vexans field-collected larvae were reared in the laboratory under field-simulated conditions. To assess the vector competence for Rift Valley fever phlebovirus (RVFV) transmission, adult F0 females were exposed to infectious blood meals containing the 56/74 RVFV strain. Additionally, intrathoracic inoculations with the same virus strain were performed to evaluate the relevance of the salivary gland barriers. Natural circulation of alphavirus, flavivirus and phlebovirus was also tested. RESULTS: To our knowledge, an autochthonous Ae. vexans population was experimentally confirmed as a competent vector for RVFV for the first time. This virus was capable of infecting and disseminating within the studied Ae. vexans mosquitoes. Moreover, infectious virus was isolated from the saliva of disseminated specimens, showing their capacity to transmit the virus. Additionally, a natural infection with a circulating Mosquito flavivirus was detected. The co-infection with the Mosquito flavivirus seemed to modulate RVFV infection susceptibility in field-collected Ae. vexans, but further studies are needed to confirm its potential interference in RVFV transmission. CONCLUSIONS: Our results show that field-collected European Ae. vexans would be able to transmit RVFV in case of introduction into the continent. This should be taken into consideration in the design of surveillance and control programmes.