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Background: West Nile virus (WNV) is an emerging mosquito-borne pathogen in Serbia, where it has been detected as a cause of infection in humans since 2012. We analyzed and modelled WNV transmission patterns in the country between 2012 and 2023. Methods: We applied a previously developed modelling approach to quantify epidemiological parameters of interest and to identify the most important environmental drivers of the force of infection (FOI) by means of statistical analysis in the human population in the country. Results: During the study period, 1,387 human cases were recorded, with substantial heterogeneity across years. We found that spring temperature is of paramount importance for WNV transmission, as FOI magnitude and peak timing are positively associated with it. Furthermore, FOI is also estimated to be greater in regions with a larger fraction of older adult people, who are at higher risk to develop severe infections. Conclusion: Our results highlight that temperature plays a key role in shaping WNV outbreak magnitude in Serbia, confirming the association between spring climatic conditions and WNV human transmission risk and thus pointing out the importance of this factor as a potential early warning predictor for timely application of preventive and control measures.
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Brotes de Enfermedades , Estaciones del Año , Fiebre del Nilo Occidental , Virus del Nilo Occidental , Serbia/epidemiología , Humanos , Fiebre del Nilo Occidental/epidemiología , Fiebre del Nilo Occidental/transmisión , Brotes de Enfermedades/estadística & datos numéricos , Adulto , Persona de Mediana Edad , Temperatura , Femenino , Anciano , Masculino , Adolescente , Animales , Adulto Joven , NiñoRESUMEN
Usutu virus (USUV), an arbovirus from the Flaviviridae family, genus Flavivirus, has recently gained increasing attention because of its potential for emergence. After his discovery in South Africa, USUV spread to other African countries, then emerged in Europe where it was responsible for epizootics. The virus has recently been found in Asia. USUV infection in humans is considered to be most often asymptomatic or to cause mild clinical signs. However, a few cases of neurological complications such as encephalitis or meningo-encephalitis have been reported in both immunocompromised and immunocompetent patients. USUV natural life cycle involves Culex mosquitoes as its main vector, and multiple bird species as natural viral reservoirs or amplifying hosts, humans and horses can be incidental hosts. Phylogenetic studies carried out showed eight lineages, showing an increasing genetic diversity for USUV. This work describes the development and validation of a novel whole-genome amplicon-based sequencing approach to Usutu virus. This study was carried out on different strains from Senegal and Italy. The new approach showed good coverage using samples derived from several vertebrate hosts and may be valuable for Usutu virus genomic surveillance to better understand the dynamics of evolution and transmission of the virus.
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Infecciones por Flavivirus , Flavivirus , Genoma Viral , Filogenia , Flavivirus/genética , Flavivirus/clasificación , Flavivirus/aislamiento & purificación , Animales , Infecciones por Flavivirus/virología , Infecciones por Flavivirus/veterinaria , Humanos , Senegal , Italia , Aves/virología , ARN Viral/genética , Variación Genética , Culex/virología , Secuenciación Completa del Genoma , Caballos/virologíaRESUMEN
Modelling approaches play a crucial role in supporting local public health agencies by estimating and forecasting vector abundance and seasonality. However, the reliability of these models is contingent on the availability of standardized, high-quality data. Addressing this need, our study focuses on collecting and harmonizing egg count observations of the mosquito Aedes albopictus, obtained through ovitraps in monitoring and surveillance efforts across Albania, France, Italy, and Switzerland from 2010 to 2022. We processed the raw observations to obtain a continuous time series of ovitraps observations allowing for an extensive geographical and temporal coverage of Ae. albopictus population dynamics. The resulting post-processed observations are stored in the open-access database VectAbundance.This initiative addresses the critical need for accessible, high-quality data, enhancing the reliability of modelling efforts and bolstering public health preparedness.
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Aedes , Animales , Bases de Datos Factuales , Mosquitos Vectores , Dinámica Poblacional , Francia , Albania , Suiza , ItaliaRESUMEN
West Nile virus (WNV) is an emerging mosquito-borne pathogen in Europe where it represents a new public health threat. While climate change has been cited as a potential driver of its spatial expansion on the continent, a formal evaluation of this causal relationship is lacking. Here, we investigate the extent to which WNV spatial expansion in Europe can be attributed to climate change while accounting for other direct human influences such as land-use and human population changes. To this end, we trained ecological niche models to predict the risk of local WNV circulation leading to human cases to then unravel the isolated effect of climate change by comparing factual simulations to a counterfactual based on the same environmental changes but a counterfactual climate where long-term trends have been removed. Our findings demonstrate a notable increase in the area ecologically suitable for WNV circulation during the period 1901-2019, whereas this area remains largely unchanged in a no-climate-change counterfactual. We show that the drastic increase in the human population at risk of exposure is partly due to historical changes in population density, but that climate change has also been a critical driver behind the heightened risk of WNV circulation in Europe.
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Culicidae , Fiebre del Nilo Occidental , Virus del Nilo Occidental , Animales , Humanos , Fiebre del Nilo Occidental/epidemiología , Cambio Climático , Europa (Continente)/epidemiologíaRESUMEN
BACKGROUND: Estimates of the spatiotemporal distribution of different mosquito vector species and the associated risk of transmission of arboviruses are key to design adequate policies for preventing local outbreaks and reducing the number of human infections in endemic areas. In this study, we quantified the abundance of Aedes albopictus and Aedes aegypti and the local transmission potential for three arboviral infections at an unprecedented spatiotemporal resolution in areas where no entomological surveillance is available. METHODS: We developed a computational model to quantify the daily abundance of Aedes mosquitoes, leveraging temperature and precipitation records. The model was calibrated on mosquito surveillance data collected in 115 locations in Europe and the Americas between 2007 and 2018. Model estimates were used to quantify the reproduction number of dengue virus, Zika virus, and chikungunya in Europe and the Americas, at a high spatial resolution. FINDINGS: In areas colonised by both Aedes species, A aegypti was estimated to be the main vector for the transmission of dengue virus, Zika virus, and chikungunya, being associated with a higher estimate of R0 when compared with A albopictus. Our estimates highlighted that these arboviruses were endemic in tropical and subtropical countries, with the highest risks of transmission found in central America, Venezuela, Colombia, and central-east Brazil. A non-negligible potential risk of transmission was also estimated for Florida, Texas, and Arizona (USA). The broader ecological niche of A albopictus could contribute to the emergence of chikungunya outbreaks and clusters of dengue autochthonous cases in temperate areas of the Americas, as well as in mediterranean Europe (in particular, in Italy, southern France, and Spain). INTERPRETATION: Our results provide a comprehensive overview of the transmission potential of arboviral diseases in Europe and the Americas, highlighting areas where surveillance and mosquito control capacities should be prioritised. FUNDING: EU and Ministero dell'Università e della Ricerca, Italy (Piano Nazionale di Ripresa e Resilienza Extended Partnership initiative on Emerging Infectious Diseases); EU (Horizon 2020); Ministero dell'Università e della Ricerca, Italy (Progetti di ricerca di Rilevante Interesse Nazionale programme); Brazilian National Council of Science, Technology and Innovation; Ministry of Health, Brazil; and Foundation of Research for Minas Gerais, Brazil.
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Aedes , Arbovirus , Fiebre Chikungunya , Infección por el Virus Zika , Virus Zika , Humanos , Animales , Fiebre Chikungunya/epidemiología , Europa (Continente)/epidemiología , Infección por el Virus Zika/epidemiologíaRESUMEN
Background: The natural transmission cycle of tick-borne encephalitis (TBE) virus is enhanced by complex interactions between ticks and key hosts strongly connected to habitat characteristics. The diversity of wildlife host species and their relative abundance is known to affect transmission of tick-borne diseases. Therefore, in the current context of global biodiversity loss, we explored the relationship between habitat richness and the pattern of human TBE cases in Europe to assess biodiversity's role in disease risk mitigation. Methods: We assessed human TBE case distribution across 879 European regions using official epidemiological data reported to The European Surveillance System (TESSy) between 2017 and 2021 from 15 countries. We explored the relationship between TBE presence and the habitat richness index (HRI1) by means of binomial regression. We validated our findings at local scale using data collected between 2017 and 2021 in 227 municipalities located in Trento and Belluno provinces, two known TBE foci in northern Italy. Findings: Our results showed a significant parabolic effect of HRI on the probability of presence of human TBE cases in the European regions included in our dataset, and a significant, negative effect of HRI on the local presence of TBE in northern Italy. At both spatial scales, TBE risk decreases in areas with higher values of HRI. Interpretation: To our knowledge, no efforts have yet been made to explore the relationship between biodiversity and TBE risk, probably due to the scarcity of high-resolution, large-scale data about the abundance or density of critical host species. Hence, in this study we considered habitat richness as proxy for vertebrate host diversity. The results suggest that in highly diverse habitats TBE risk decreases. Hence, biodiversity loss could enhance TBE risk for both humans and wildlife. This association is relevant to support the hypothesis that the maintenance of highly diverse ecosystems mitigates disease risk.
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Aedes japonicus and Aedes koreicus are two invasive mosquitoes native to East Asia that are quickly establishing in temperate regions of Europe. Both species are vectors of arboviruses, but we currently lack a clear understanding of their evolution. Here, we present new short-read, shallow genome sequencing of A. japonicus and A. koreicus individuals from northern Italy, which we used for downstream phylogenetic and barcode analyses. We explored associated microbial DNA and found high occurrences of Delftia bacteria in both samples, but neither Asaia nor Wolbachia. We then assembled complete mitogenomes and used these data to infer divergence times estimating the split of A. japonicus from A. koreicus in the Oligocene, which was more recent than that previously reported using mitochondrial markers. We recover a younger age for most other nodes within Aedini and other Culicidae. COI barcoding and phylogenetic analyses indicate that A. japonicus yaeyamensis, A. japonicus amamiensis, and the two A. koreicus sampled from Europe should be considered as separate species within a monophyletic species complex. Our studies further clarify the evolution of A. japonicus and A. koreicus, and indicate the need to obtain whole-genome data from putative species in order to disentangle their complex patterns of evolution.
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BackgroundTick-borne encephalitis (TBE) is a disease which can lead to severe neurological symptoms, caused by the TBE virus (TBEV). The natural transmission cycle occurs in foci and involves ticks as vectors and several key hosts that act as reservoirs and amplifiers of the infection spread. Recently, the incidence of TBE in Europe has been rising in both endemic and new regions.AimIn this study we want to provide comprehensive understanding of the main ecological and environmental factors that affect TBE spread across Europe.MethodsWe searched available literature on covariates linked with the circulation of TBEV in Europe. We then assessed the best predictors for TBE incidence in 11 European countries by means of statistical regression, using data on human infections provided by the European Surveillance System (TESSy), averaged between 2017 and 2021.ResultsWe retrieved data from 62 full-text articles and identified 31 different covariates associated with TBE occurrence. Finally, we selected eight variables from the best model, including factors linked to vegetation cover, climate, and the presence of tick hosts.DiscussionThe existing literature is heterogeneous, both in study design and covariate types. Here, we summarised and statistically validated the covariates affecting the variability of TBEV across Europe. The analysis of the factors enhancing disease emergence is a fundamental step towards the identification of potential hotspots of viral circulation. Hence, our results can support modelling efforts to estimate the risk of TBEV infections and help decision-makers implement surveillance and prevention campaigns.
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Virus de la Encefalitis Transmitidos por Garrapatas , Encefalitis Transmitida por Garrapatas , Ixodes , Garrapatas , Animales , Humanos , Encefalitis Transmitida por Garrapatas/prevención & control , Europa (Continente)/epidemiología , ClimaRESUMEN
It is unclear whether West Nile virus (WNV) circulates between Africa and Europe, despite numerous studies supporting an African origin and high transmission in Europe. We integrated genomic data with geographic observations and phylogenetic and phylogeographic inferences to uncover the spatial and temporal viral dynamics of WNV between these two continents. We focused our analysis towards WNV lineages 1 (L1) and 2 (L2), the most spatially widespread and pathogenic WNV lineages. Our study shows a Northern-Western African origin of L1, with back-and-forth exchanges between West Africa and Southern-Western Europe; and a Southern African origin of L2, with one main introduction from South Africa to Europe, and no back introductions observed. We also noticed a potential overlap between L1 and L2 Eastern and Western phylogeography and two Afro-Palearctic bird migratory flyways. Future studies linking avian and mosquito species susceptibility, migratory connectivity patterns, and phylogeographic inference are suggested to elucidate the dynamics of emerging viruses.
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Fiebre del Nilo Occidental , Virus del Nilo Occidental , Animales , Virus del Nilo Occidental/genética , Filogenia , Europa (Continente)/epidemiología , Sudáfrica , AvesRESUMEN
West Nile virus is a re-emerging arbovirus whose impact on public health is increasingly important as more and more epidemics and epizootics occur, particularly in America and Europe, with evidence of active circulation in Africa. Because birds constitute the main reservoirs, migratory movements allow the diffusion of various lineages in the world. It is therefore crucial to properly control the dispersion of these lineages, especially because some have a greater health impact on public health than others. This work describes the development and validation of a novel whole-genome amplicon-based sequencing approach to West Nile virus. This study was carried out on different strains from lineage 1 and 2 from Senegal and Italy. The presented protocol/approach showed good coverage using samples derived from several vertebrate hosts and may be valuable for West Nile genomic surveillance.
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Fiebre del Nilo Occidental , Virus del Nilo Occidental , Animales , Humanos , Virus del Nilo Occidental/genética , Fiebre del Nilo Occidental/epidemiología , Fiebre del Nilo Occidental/veterinaria , Europa (Continente)/epidemiología , Italia , SenegalRESUMEN
Tick-borne encephalitis (TBE) is caused by a flavivirus that infects animals including humans. In Europe, the TBE virus circulates enzootically in natural foci among ticks and rodent hosts. The abundance of ticks depends on the abundance of rodent hosts, which in turn depends on the availability of food resources, such as tree seeds. Trees can exhibit large inter-annual fluctuations in seed production (masting), which influences the abundance of rodents the following year, and the abundance of nymphal ticks two years later. Thus, the biology of this system predicts a 2-year time lag between masting and the incidence of tick-borne diseases such as TBE. As airborne pollen abundance is related to masting, we investigated whether inter-annual variation in pollen load could be directly correlated with inter-annual variation in the incidence of TBE in human populations with a 2-year time lag. We focused our study on the province of Trento (northern Italy), where 206 TBE cases were notified between 1992 and 2020. We tested the relationship between TBE incidence and pollen load collected from 1989 to 2020 for 7 different tree species common in our study area. Through univariate analysis we found that the pollen quantities recorded two years prior for two tree species, hop-hornbeam (Ostrya carpinifolia) and downy oak (Quercus pubescens), were positively correlated with TBE emergence (R2 = 0.2) while a multivariate model with both tree species better explained the variation in annual TBE incidence (R2 = 0.34). To the best of our knowledge, this is the first attempt at quantifying the correlation between pollen quantities and the incidence of TBE in human populations. As pollen loads are collected by widespread aerobiological networks using standardized procedures, our study could be easily replicated to test their potential as early warning system for TBE and other tick-borne diseases.
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Ciervos , Encefalitis Transmitida por Garrapatas , Ixodes , Garrapatas , Humanos , Animales , Encefalitis Transmitida por Garrapatas/epidemiología , Italia/epidemiología , Incidencia , Roedores , Árboles , PolenRESUMEN
Global change is expected to have complex effects on the distribution and transmission patterns of zoonotic parasites. Modelling habitat suitability for parasites with complex life cycles is essential to further our understanding of how disease systems respond to environmental changes, and to make spatial predictions of their future distributions. However, the limited availability of high quality occurrence data with high spatial resolution often constrains these investigations. Using 449 reliable occurrence records for Echinococcus multilocularis from across Europe published over the last 35 years, we modelled habitat suitability for this parasite, the aetiological agent of alveolar echinococcosis, in order to describe its environmental niche, predict its current and future distribution under three global change scenarios, and quantify the probability of occurrence for each European country. Using a machine learning approach, we developed large-scale (25 × 25 km) species distribution models based on seven sets of predictors, each set representing a distinct biological hypothesis supported by current knowledge of the autecology of the parasite. The best-supported hypothesis included climatic, orographic and land-use/land-cover variables such as the temperature of the coldest quarter, forest cover, urban cover and the precipitation seasonality. Future projections suggested the appearance of highly suitable areas for E. multilocularis towards northern latitudes and in the whole Alpine region under all scenarios, while decreases in habitat suitability were predicted for central Europe. Our spatially explicit predictions of habitat suitability shed light on the complex responses of parasites to ongoing global changes.
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Equinococosis , Echinococcus multilocularis , Parásitos , Animales , Echinococcus multilocularis/fisiología , Equinococosis/epidemiología , Equinococosis/parasitología , Europa (Continente) , Ecosistema , Estadios del Ciclo de Vida , Cambio ClimáticoRESUMEN
West Nile virus (WNV) is among the most recent emerging mosquito-borne pathogens in Europe where each year hundreds of human cases are recorded. We developed a relatively simple technique to model the WNV force of infection (FOI) in the human population to assess its dependence on environmental and human demographic factors. To this aim, we collated WNV human case-based data reported to the European Surveillance System from 15 European Countries during the period 2010-2021. We modelled the regional WNV FOI for each year through normal distributions and calibrated the constituent parameters, namely average (peak timing), variance and overall intensity, to observed cases. Finally, we investigated through regression models how these parameters are associated to a set of climatic, environmental and human demographic covariates. Our modelling approach shows good agreement between expected and observed epidemiological curves. We found that FOI magnitude is positively associated with spring temperature and larger in more anthropogenic semi-natural areas, while FOI peak timing is negatively related to summer temperature. Unsurprisingly, FOI is estimated to be greater in regions with a larger fraction of elderly people, who are more likely to contract severe infections. Our results confirm that temperature plays a key role in shaping WNV transmission in Europe and provide some interesting hints on how human presence and demography might affect WNV burden. This simple yet reliable approach could be easily adopted for early warning and to address epidemiological investigations of other vector-borne diseases, especially where eco-epidemiological data are scarce.
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Mosquito species belonging to the genus Aedes have attracted the interest of scientists and public health officers because of their capacity to transmit viruses that affect humans. Some of these species were brought outside their native range by means of trade and tourism and then colonised new regions thanks to a unique combination of eco-physiological traits. Considering mosquito physiological and behavioural traits to understand and predict their population dynamics is thus a crucial step in developing strategies to mitigate the local densities of invasive Aedes populations. Here, we synthesised the life cycle of four invasive Aedes species (Ae. aegypti, Ae. albopictus, Ae. japonicus and Ae. koreicus) in a single multi-scale stochastic modelling framework which we coded in the R package dynamAedes. We designed a stage-based and time-discrete stochastic model driven by temperature, photo-period and inter-specific larval competition that can be applied to three different spatial scales: punctual, local and regional. These spatial scales consider different degrees of spatial complexity and data availability by accounting for both active and passive dispersal of mosquito species as well as for the heterogeneity of the input temperature data. Our overarching aim was to provide a flexible, open-source and user-friendly tool rooted in the most updated knowledge on the species' biology which could be applied to the management of invasive Aedes populations as well as to more theoretical ecological inquiries.
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Aedes , Humanos , Animales , Aedes/fisiología , Larva/fisiología , Especies Introducidas , Dinámica Poblacional , Temperatura , Mosquitos Vectores/fisiologíaRESUMEN
Aedes koreicus is an invasive mosquito species which has been introduced into several European countries. Compared to other invasive Aedes mosquitoes, little is known of its biology and ecology. To determine Ae. koreicus' vectorial capacity, it is essential to establish its feeding patterns and level of anthropophagy. We report on the blood-feeding patterns of Ae. koreicus, examining the blood meal origin of engorged females and evaluating the influence of different biotic and abiotic factors on feeding behavior. Mosquitoes were collected in 23 sites in northern Italy by manual aspiration and BG-sentinel traps; host availability was estimated by survey. The source of blood meals was identified using a nested PCR and by targeting and sequencing the cytochrome c oxidase subunit I gene. In total, 352 Ae. koreicus engorged females were collected between 2013 and 2020 and host blood meals were determined from 299 blood-fed mosquitoes (84.9%). Eleven host species were identified, with the highest prevalences being observed among roe deer (Capreolus capreolus) (N = 189, 63.2%) and humans (N = 46, 15.4%). Blood meals were mostly taken from roe deer in forested sites and from humans in urban areas, suggesting that this species can feed on different hosts according to local abundance. Two blood meals were identified from avian hosts and one from lizard. Ae. koreicus' mammalophilic feeding pattern suggests that it may be a potential vector of pathogens establishing transmission cycles among mammals, whereas its role as a bridge vector between mammals and birds could be negligible.
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Aedes , Ciervos , Aedes/genética , Animales , Aves , Complejo IV de Transporte de Electrones , Europa (Continente) , Conducta Alimentaria , Femenino , Humanos , Especies Introducidas , Mosquitos Vectores/genéticaRESUMEN
Aedes koreicus is an invasive alien mosquito species native to Asia now introduced in several European countries, including northern Italy. In this temperate region, mosquito populations survive cold winter temperatures thanks to diapausing eggs or adults, depending on the species. In its native area, Ae. koreicus was reported to overwinter in the egg stage, but to the best of our knowledge, it is not confirmed whether overwintering eggs are actually diapausing or only in a quiescence stage, i.e., they might hatch as soon as external conditions are favorable. Based on previous laboratory studies, we established a diapausing Ae. koreicus colony, maintained at 21 °C with a photoperiod of 12L:12D. Females were allowed to lay eggs, which were consequently placed in water at different time intervals after oviposition, from 30 days to 5 months. We found that diapausing eggs younger than 3 months have a poor hatching rate, while after about 100 days we observed that almost all eggs hatched. Our findings highlight that water immersion alone did not lead to the hatching of eggs, as age was found to be a significantly important factor. We thus confirm effective diapause, occurring at the egg stage, for Ae. koreicus in a recently invaded area. Moreover, our quantification of diapause duration and hatching success might help in better designing future experiments and improving modeling efforts.
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Aedes , Diapausa , Animales , Femenino , Especies Introducidas , Oviposición , AguaRESUMEN
In January 2022, West Nile virus (WNV) lineage 2 (L2) was detected in an adult female goshawk rescued near Perugia in the region of Umbria (Italy). The animal showed neurological symptoms and died 15 days after its recovery in a wildlife rescue center. This was the second case of WNV infection recorded in birds in the Umbria region during the cold season, when mosquitoes, the main WNV vectors, are usually not active. According to the National Surveillance Plan, the Umbria region is included amongst the WNV low-risk areas. The necropsy evidenced generalized pallor of the mucous membranes, mild splenomegaly, and cerebral edema. WNV L2 was detected in the brain, heart, kidney, and spleen homogenate using specific RT-PCR. Subsequently, the extracted viral RNA was sequenced. A Bayesian phylogenetic analysis performed through a maximum-likelihood tree showed that the genome sequence clustered with the Italian strains within the European WNV strains among the central-southern European WNV L2 clade. These results, on the one hand, confirmed that the WNV L2 strains circulating in Italy are genetically stable and, on the other hand, evidenced a continuous WNV circulation in Italy throughout the year. In this report case, a bird-to-bird WNV transmission was suggested to support the virus overwintering. The potential transmission through the oral route in a predatory bird may explain the relatively rapid spread of WNV, as well as other flaviviruses characterized by similar transmission patterns. However, rodent-to-bird transmission or mosquito-to-bird transmission cannot be excluded, and further research is needed to better understand WNV transmission routes during the winter season in Italy.
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Epidermal Patterning Factor Like 9 (EPFL9), also known as STOMAGEN, is a cysteine-rich peptide that induces stomata formation in vascular plants, acting antagonistically to other epidermal patterning factors (EPF1, EPF2). In grapevine there are two EPFL9 genes, EPFL9-1 and EPFL9-2 sharing 82% identity at protein level in the mature functional C-terminal domain. In this study, CRISPR/Cas9 system was applied to functionally characterize VvEPFL9-1 in 'Sugraone', a highly transformable genotype. A set of plants, regenerated after gene transfer in embryogenic calli via Agrobacterium tumefaciens, were selected for evaluation. For many lines, the editing profile in the target site displayed a range of mutations mainly causing frameshift in the coding sequence or affecting the second cysteine residue. The analysis of stomata density revealed that in edited plants the number of stomata was significantly reduced compared to control, demonstrating for the first time the role of EPFL9 in a perennial fruit crop. Three edited lines were then assessed for growth, photosynthesis, stomatal conductance, and water use efficiency in experiments carried out at different environmental conditions. Intrinsic water-use efficiency was improved in edited lines compared to control, indicating possible advantages in reducing stomatal density under future environmental drier scenarios. Our results show the potential of manipulating stomatal density for optimizing grapevine adaptation under changing climate conditions.
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Culex pipiens (Linnaeus), one of the most abundant mosquito species in Europe, plays a crucial role in the endemic transmission of West Nile virus and caused the large outbreak with >1600 human cases in 2018. Although evidence of resistance to pyrethroids has been reported for Cx. pipiens populations from Spain and Greece, resistance monitoring has been largely neglected in Italy. Herein, we investigate susceptibility of Italian Cx. pipiens populations to the pyrethroids permethrin and deltamethrin. Results from WHO-tube-bioassays revealed mortalities ranging from 14-54%, indicating high levels of resistance, in four out of 10 populations exposed to permethrin (0.75%) and of 63% in one of three populations exposed to deltamethrin (0.05%). Reduced susceptibility (mortality<98%) was detected in almost all other populations. A clear association is shown between the resistant phenotype and the presence of kdr-alleles in position 1014 of the VSSC, strongly suggesting its role in reducing susceptibility. The study provides the first evidence of pyrethroid-resistance in Italian Cx. pipiens populations and reports levels of resistance paralleled in the European region only in Turkey. This highlights the urgent need to implement insecticide-resistance management plans to restore the efficacy of the nowadays only chemical weapon available to control arbovirus transmission in Europe.
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Culex , Resistencia a los Insecticidas , Insecticidas , Piretrinas , Virus del Nilo Occidental , Animales , Culex/genética , Culex/virología , Resistencia a los Insecticidas/genética , Italia , Mosquitos Vectores , PermetrinaRESUMEN
BACKGROUND: Trentino is an Italian province with a tourism-based economy, bordering the regions of Lombardy and Veneto, where the two earliest and largest outbreaks of COVID-19 occurred in Italy. The earliest cases in Trentino were reported in the first week of March 2020, with most of the cases occurring in the winter sport areas in the Dolomites mountain range. The number of reported cases decreased over the summer months and was followed by a second wave in the autumn and winter of 2020. METHODS: we performed high-coverage Oxford Nanopore sequencing of 253 positive SARS-CoV-2 swabs collected in Trentino between March and December 2020. RESULTS: in this work, we analyzed genome sequences to trace the routes through which the virus entered the area, and assessed whether the autumnal resurgence could be attributed to lineages persisting undetected during summer, or as a consequence of new introductions. CONCLUSIONS: Comparing the draft genomes analyzed with a large selection of European sequences retrieved from GISAID we found that multiple introductions of the virus occurred at the early stage of the epidemics; the two epidemic waves were unrelated; the second wave was due to reintroductions of the virus in summer when traveling restrictions were uplifted.