Presence Of West Nile Virus Research Articles

PRELIMINARY DATA REGARDING DOGS AS WNV SENTINELS

West Nile Virus (WNV) is a mosquito-borne flavivirus that has a zoonotic character determining an inapparent infection, mild unspecific symptoms as flu like manifestations or a severe encephalitis, and can also affect other mammals, including dogs. Most dogs exposed to WNV exhibit mild symptoms such transient fever, lethargy, or loss of appetite. Severe neurological manifestations, including ataxia, seizures, and paralysis, are rare but can occur in immunocompromised or highly exposed animals. The role of dogs as amplifying hosts is minimal due to low-level viremia. However, despite the relatively low risk to dogs, the presence of WNV in canine populations reflects broader environmental and public health concerns, as it can serve as a marker for potential human exposure. This preliminary study aimed to verify the hypothesis of dogs as indicators of WNV evolution. Samples collected in 2023 and 2022 from a public dog shelter and a veterinary private clinic from Iasi County were tested for the presence of specific anti WNV antibodies. The results showed and overall prevalence of 37,5% [(IC 95% (27.38 - 47.62)] in the dog samples collected from the dog shelter and a 18,4% [(IC 95% (10.96-25.94)] in the samples collected from the private practice. Those are in accordance with the epidemiological situation in humans in 2023 and 2022 in the County. The study is preliminary and intend to add data to the international research. Further analyses are needed to clarify if dogs can be considered sentinels for WNV infection in humans.

Circulation of West Nile virus and Usutu virus in birds in Germany, 2021 and 2022

Background Usutu virus (USUV) and West Nile virus (WNV) are zoonotic arthropod-borne orthoflaviviruses. The enzootic transmission cycles of both include Culex mosquitoes as vectors and birds as amplifying hosts. For more than 10 years, these viruses have been monitored in birds in Germany by a multidisciplinary network. While USUV is present nationwide, WNV used to be restricted to the central-east. Methods In 2021 and 2022, over 2300 live bird blood samples and organs from over 3000 deceased birds were subjected to molecular and serological analysis regarding the presence of WNV and USUV. The samples were collected at sites all over Germany. Results Circulation of both viruses increased in 2022. For USUV, the nationwide presence of lineages Africa 3 and Europe 3 reported in previous years was confirmed. Lineage Europe 2, formerly restricted to the German east, was able to expand westward. Nonetheless, USUV neutralizing antibody (nAb) detection rates remained low (< 9%). Years 2021 and 2022 were characterized by stable enzootic circulation of WNV lineage 2, dominated by one previously identified subcluster (95% of generated sequences). In 2022, >20% of birds in the endemic region in eastern Germany carried nAb against WNV. Serological data also indicate expanding WNV circulation west and south of the known hotspots in Germany. Conclusions USUV circulates enzootically nationwide. Emergence of WNV at several new locations in Germany with a potential increase in human infections may be imminent. In this context, wild bird monitoring serves as a capable early warning system in a One Health setting.

West Nile virus in adults and larvae of Culiseta longiareolata and Culex hortensis (Diptera: Culicidae) captured in Hamedan, western Iran

West Nile virus in adults and larvae of Culiseta longiareolata and Culex hortensis (Diptera: Culicidae) captured in Hamedan, western Iran

Epidemiological Aspects of the Incidence of West Nile Fever in the Republic of Tatarstan in 2023

The aim of the work was to study the epidemiological situation on West Nile fever (WNF) in the Republic of Tatarstan in 2023.Materials and methods. An operational epidemiological analysis of WNF cases registered in the Republic of Tatarstan in 2023 was performed. In order to establish sources and risk factors for infection of the population, 987 samples of zoo-entomological material were examined for the presence of West Nile virus (WNV) markers. A set of laboratory diagnostic methods was used: ELISA, RT-PCR, sequencing.Results and discussion. It has been established that all cases of WNF were registered in the region in the summer-autumn period of 2023, mainly in August, among residents of the city of Kazan who had not traveled outside the Russian Federation and the Republic of Tatarstan over the past six months. The incidence rate of WNF in the Republic of Tatarstan was 0.20 per 100 thousand population, the mortality rate reached 12.5 %. Signs of damage to the central nervous system were present in 6 out of 8 (75 %) patients. The majority of people with severe clinical symptoms belonged to older age groups and had concomitant diseases. Cases of the infection were reported in all age groups, with the exception of children and adolescents. The spatial characteristics of morbidity have been investigated, indicating the diffuse nature of the distribution of cases. The integrated use of methods, consisting in the concurrent use of polymerase chain reaction and enzyme-linked immunosorbent assay, made it possible to laboratory confirm cases of WNF in patients at different stages of the disease. The circulation of a subvariant of the WNV of the second genotype in the Republic of Tatarstan, currently dominant in the southern and central regions of Russia, has been established. A set of measures has been proposed to optimize epidemiological surveillance and control of WNF in the Republic of Tatarstan.

Forecasting West Nile Virus With Graph Neural Networks: Harnessing Spatial Dependence in Irregularly Sampled Geospatial Data.

Machine learning methods have seen increased application to geospatial environmental problems, such as precipitation nowcasting, haze forecasting, and crop yield prediction. However, many of the machine learning methods applied to mosquito population and disease forecasting do not inherently take into account the underlying spatial structure of the given data. In our work, we apply a spatially aware graph neural network model consisting of GraphSAGE layers to forecast the presence of West Nile virus in Illinois, to aid mosquito surveillance and abatement efforts within the state. More generally, we show that graph neural networks applied to irregularly sampled geospatial data can exceed the performance of a range of baseline methods including logistic regression, XGBoost, and fully-connected neural networks.

Accelerating targeted mosquito control efforts through mobile West Nile virus detection.

Different mosquito control strategies have been implemented to mitigate or prevent mosquito-related public health situations. Modern mosquito control largely relies on multiple approaches, including targeted, specific treatments. Given this, it is becoming increasingly important to supplement these activities with rapid and mobile diagnostic capacities for mosquito-borne diseases. We aimed to create and test the applicability of a rapid diagnostic system for West Nile virus that can be used under field conditions. In this pilot study, various types of adult mosquito traps were applied within the regular mosquito monitoring activity framework for mosquito control. Then, the captured specimens were used for the detection of West Nile virus RNA under field conditions with a portable qRT-PCR approach within 3-4h. Then, positive samples were subjected to confirmatory RT-PCR or NGS sequencing in the laboratory to obtain genome information of the virus. We implemented phylogenetic analysis to characterize circulating strains. A total of 356 mosquito individuals representing 7 species were processed in 54 pools, each containing up to 20 individuals. These pools were tested for the presence of West Nile virus, and two pools tested positive, containing specimens from the Culex pipiens and Anopheles atroparvus mosquito species. As a result of subsequent sequencing, we present the complete genome of West Nile virus and Bagaza virus. The rapid identification of infected mosquitoes is the most important component of quick response adulticide or larvicide treatments to prevent human cases. The conceptual framework of real-time surveillance can be optimized for other pathogens and situations not only in relation to West Nile virus. We present an early warning system for mosquito-borne diseases and demonstrate its application to aid rapid-response mosquito control actions.

West Nile Virus Monitoring in Flanders (Belgium) During 2022–2023 Reveals Endemic Usutu Virus Circulation in Birds

The recent emergence of West Nile virus (WNV) and Usutu virus (USUV) in some European countries has triggered an increase in animal and human cases across Europe. Wild birds, serving as key reservoirs for WNV and USUV, often act as crucial indicators for the introduction and spread of these viruses. Currently, there is no durable large‐scale monitoring for WNV in Belgium, and specific monitoring for USUV is lacking. In Flanders, passive WNV monitoring in birds has been in place for many years, while initial efforts to initiate active monitoring started in 2022. Here, we present the results of a limited study conducted during the vector seasons of 2022 and 2023 in Flemish bird populations to actively and passively monitor the prevalence of WNV and additionally assess the presence of USUV. Several real‐time reverse transcription‐PCR tests were employed for virus detection, revealing the absence of WNV‐RNA during both vector seasons. Conversely, USUV‐RNA was identified in 2022 through active surveillance, affecting two (5.5%) out of 36 birds (Corvus corone), and in passive surveillance, impacting eight (72.7%) out of 11 birds (Turdus merula [6] and Rhea pennata [2]). In 2023, active surveillance was more extensive and identified 16 (7.2%) USUV‐RNA positive birds (Buteo buteo [1], T. merula [14] and Athene noctua [1]) out of 222 examined birds, while passive surveillance detected two (7.1%) positive birds (T. merula [1], and Larus marinus [1]) out of 28. Viral sequence information was obtained from seven USUV‐positive birds using whole genome sequencing or Sanger sequencing. Phylogenetic analysis placed all identified strains within the Africa 3 lineage. This restricted WVN monitoring effort in Flanders did not reveal WNV presence, but found indications of an endemic USUV circulation in Belgium. It is crucial to intensify monitoring efforts for WNV in the coming years, considering its endemic status in several European countries and its expanding geographical range in northern Europe.

First Detection of West Nile Virus Lineage 2 in Mosquitoes in Switzerland, 2022.

West Nile virus (WNV) is one of the most widespread flaviviruses in the world, and in recent years, it has been frequently present in many Mediterranean and Eastern European countries. A combination of different conditions, such as a favourable climate and higher seasonal average temperatures, probably allowed its introduction and spread to new territories. In Switzerland, autochthonous cases of WNV have never been reported, and the virus was not detected in mosquito vectors until 2022, despite an entomological surveillance in place in Canton Ticino, southern Switzerland, since 2010. In 2022, 12 sites were monitored from July to October, using BOX gravid mosquito traps coupled with honey-baited FTA cards. For the first time, we could detect the presence of WNV in FTA cards and mosquitoes in 8 out of the 12 sampling sites monitored, indicating an unexpectedly widespread circulation of the virus throughout the territory. Positive findings were recorded from the beginning of August until mid-October 2022, and whole genome sequencing analysis identified a lineage 2 virus closely related to strains circulating in Northern Italy. The entomological surveillance has proved useful in identifying viral circulation in advance of possible cases of WNV infection in humans or horses.

The first serological detection of West Nile virus infection among residents living in northern Turkey.

West Nile virus (WNV) is transmitted by a mosquito-borne virus whose natural reservoir is birds. Humans and horses are considered accidental hosts. Even if the vast majority of WNV infections in humans have asymptomatic or mild disease settings, serious neurological disorders with lethal outcomes can also be observed in around 1% of the cases. We aimed to serologically investigate the presence of WNV in humans living in Black sea of Turkey, and to obtain epidemiological data that will contribute to the implementation of public health policies to control and prevent potentially other life-threatening arboviral infections. In the current study, a total of 416 human sera were collected from native patients of Samsun and its boroughs attending Samsun Training and Research Hospital; these sera were tested for WNV with pooling method, using anti-IgM and IgG ELISA commercial kits. All pools that were found positive for both IgM and IgG were individually retested for the detection of positive WNV sera. After that, all positive samples were tested using real-time PCR to detect the presence of WNV-RNA particles. Total seropositivity rates of WNV in terms of IgM and IgG were found as 0.96% and 0.72%, respectively. No presence of WNV-RNA could be detected in positive samples. According to the data, further studies should be conducted to better understand the epidemiological dynamics of WNV in Turkey. It is recommended that other antigenically related flaviviruses which can give cross-reaction with WNV should also be investigated.

Species of mosquitoes present in Abruzzo and Molise and their possible role as vector of Usutu and West Nile viruses.

In 2019, entomological survey on mosquitoes was carried out in Abruzzo and Molise regions in central Italy to obtain data on local mosquito fauna. Collection sites were selected based on a previous ecoregion classification of the territory. From 2019 to 2021 virological surveillance for West Nile virus (WNV) and Usutu virus (USUV) on mosquitoes was carried out in the same regions, selecting ecoregions where virus circulation and vector presence were more likely, all mosquitoes were collected and identified, and the female mosquitoes were sorted in 3046 pools and tested for the presence of WNV and USUV by Real-time PCR. All pools tested negative for WND, while USUV was detected in 7 pools of Aedes caspius collected in Molise region, 17 pools of Culex pipiens s.l. (2 collected in Molise, 15 in Abruzzo), and 1 pool of Culiseta longiareolata collected in Molise. These results suggests the presence of an USUV enzootic cycle, maintained by Culex pipiens s.l. and Aedes caspius in both Italian regions, as well as providing a useful picture in terms of species presence and abundance for both regions. Ecoregions proved to be a very valuable tool in determining high risk areas for vector borne diseases.

Entomological Surveillance Activities in Regions in Greece: Data on Mosquito Species Abundance and West Nile Virus Detection in Culex pipiens Pools (2019-2020).

Human cases of West Nile virus (WNV) infections have been recorded in Greece since 2010, with seasonal outbreaks (summer-autumn) on an almost annual basis, caused mainly by the WNV lineage 2 strain (Nea Santa-Greece-2010). National Public Health Organization (NPHO) in Greece is annually implementing enhanced surveillance of human WNV infection, in order to promptly identify human cases of WNV infection and monitor distribution in terms of time and place. Entomological surveillance activities were carried out on a national basis in 2019 and 2020, under NPHO coordination and the collaboration of several private subcontractors, along with the Unit of Medical Entomology, Laboratory for Surveillance of Infectious Diseases (LSID). The aim was to monitor mosquito species composition, abundance, and WNV circulation in mosquito pools of Culex pipiens s.l. species. Adult mosquito traps were placed in selected sites; collected samples were morphologically characterized and pooled by date of collection, location, and species types. Female Culex pipiens s.l. pools were tested for WNV and WNV infection rates (MIR and MLE) were estimated. Highest mean number of female Culex pipiens s.l. species was recorded in Central Macedonia both for 2019 and 2020. Six hundred and fifty-nine mosquito pools (147 in 2019 and 512 in 2020) of female Culex pipiens s.l. were examined for WNV presence. The highest MLE was detected in Western Macedonia in 2019 and in Thessaly in 2020. Here, we present data on the mosquito species composition in the studied areas and WNV detection in mosquitoes from areas in Greece where the specific national mosquito surveillance program was implemented, for two years, 2019 and 2020.

Competence of mosquitoes &lt;i&gt;Culex pipiens f.&lt;/i&gt; molestus as carriers of West Nile virus under various temperature conditions

Introduction. The Culex pipiens mosquito is one of the proven vectors of the West Nile virus (WNV). Culex pipiens f. molestus (Cx. p. f. molestus) is a synanthropic, autogenous, widespread form of the species that can feed on a broad range of hosts, including humans. The temperature of the habitat of insects affects the potential for virus transmission, which determines the likelihood of them carrying the pathogen of West Nile fever.&#x0D; The goal is an experimental study of the temperature of the habitat of larvae on the competence of mosquitoes Cx. p. f. molestus as carriers of WNV.&#x0D; Materials and methods. We used a strain of the WNV (WNV_Volg601/18 genotype 2) and a laboratory culture of mosquitoes Cx. p. f. molestus. The concentration of the virus was detected by plaque formation using Vero cells. Insects were infected orally at the larval stage, with subsequent incubation at 20, 22 or 28C. 72 hours after the emergence of all adults from the pupae, the mosquitoes were immobilized by cold, the sex of imago was determined, the salivary glands were isolated from the females, and the presence of WNV in glandes and its titer were detected.&#x0D; Results. The titer of WNV sufficient to transmit the pathogen through the insect biting was observed in the salivary glands of insects kept at a temperature of 22 and 28C, with the virus titer rising with the temperature increasing. No virus was detected in the salivary glands of female insects kept at a temperature of 20C.&#x0D; Conclusion. Thus, it appears that the habitat temperature is an important factor limiting the replication and content of WNV in the salivary glands of Cx. p. f. molestus.

Arbovirus persistence in North-Western Europe: Are mosquitoes the only overwintering pathway?

In some areas in temperate Europe, genomic analyses of mosquito-borne virus outbreaks have revealed the presence of similar virus strains over several years, indicating local overwintering of these viruses. However, it remains unclear how mosquito-borne viruses can persist in winter, when conditions are generally unfavourable for virus circulation. One of the presumed routes of virus persistence is via diapausing mosquitoes. Here, we set out to study whether arbovirus persistence of West Nile virus (WNV), Usutu virus (USUV) and Sindbis virus (SINV) occurs in diapausing mosquitoes in the Netherlands. To this end, mosquito collections were carried out in the winter of 2020 and 2021, in hibernacula located in two areas with previously observed WNV and/or USUV activity. In total, we collected 4200 mosquitoes belonging to four species (Culex pipiens, Culiseta annulata, Anopheles maculipennis s.l., and Culex territans), which were pooled in 490 monospecific pools. These pools were subjected to WNV-, USUV- and SINV-screening using a multiplex real-time RT-PCR assay. All mosquito pools tested negative for the presence of WNV, USUV and SINV RNA. Consequently, we did not find evidence of arbovirus persistence in diapausing mosquitoes in the Netherlands, even though USUV and WNV have re-appeared in birds and/or mosquitoes during the summer seasons of 2020–2022. Concluding, given the persistence of USUV and WNV in the Netherlands and SINV in other temperate regions, this study highlights the importance of further research on (alternative) arbovirus overwintering routes.

Using Rapid Analyte Measurement Platform (RAMP) as a Tool for an Early Warning System Assessing West Nile Virus Epidemiological Risk in Bucharest, Romania.

West Nile virus (WNV) is the most widely spread arbovirus in the world. Early detection of this virus in mosquito populations is essential for implementing rapid vector control measures to prevent outbreaks. Real-time reverse transcription polymerase chain reaction (real-time RT-PCR) is a powerful tool for the detection of WNV in mosquito pools, but it is a time- and resource-consuming assay. We used a Rapid Analyte Measurement Platform (RAMP) assay in a vector surveillance program for rapid detection of WNV in mosquitoes collected in Bucharest city, Romania, in 2021. The positive mosquito pools were tested for confirmation with real-time RT-PCR. Three out of the 24 RAMP assay positive pools were not confirmed by real-time RT-PCR. We consider that RAMP assay can be used as a fast and reliable method for the screening of WNV presence in mosquito pools, but we recommend that samples with values ranging from 30 to 100 RAMP units should fall in a grey zone and should be considered for real-time RT-PCR confirmation.

West Nile Virus and Usutu Virus: A Post-Mortem Monitoring Study in Wild Birds from Rescue Centers, Central Italy.

West Nile virus (WNV) and Usutu virus (USUV) are mosquito-borne flaviviruses that have been associated with neurological diseases in humans and wild birds. Wild bird rescue centers are potential significant hot spots for avian infection surveillance, as recognized in the Italian Integrate National Surveillance Plan for Arboviruses. Here we report the results of a post-mortem active monitoring study conducted from November 2017 to October 2020 on animals hosted in five wild bird rescue centers of Central Italy. Five hundred seventy-six (n = 576) wild birds were tested by real-time polymerase chain reaction (RT-PCR) for the presence of WNV or USUV RNA fragments. No birds tested positive for USUV RNA (n = 0; 0.00%). Evidence of WNV RNA (Ct value = 34.36) was found in one bird (n = 1; 0.17%), an adult little grebe (Tachybaptus ruficollis subsp. ruficollis), that tested WNV positive in December 2019. This study highlights the strategic role of wildlife rescue centers in monitoring both the introduction and circulation of avian emerging zoonotic diseases. In addition, the presence of WNV during the cold season evidences the possible role of birds in overwintering mechanisms in the Italian territory and requires further investigations.

West Nile Virus Occurrence and Ecological Niche Modeling in Wild Bird Species and Mosquito Vectors: An Active Surveillance Program in the Peloponnese Region of Greece.

West Nile Virus (WNV) is maintained in nature in a bird-mosquito cycle and human infections follow a seasonal pattern, favored by climatic conditions. Peloponnese Region, located in Southern Greece, initiated an active WNV surveillance program to protect public health during 2019–2020. The project included monitoring of avian hosts and mosquito vectors, while sampling locations were prioritized after consideration of WNV circulation in birds, mosquitos and humans during previous seasons. Biological materials were collected from 493 wild birds of 25 species and 678 mosquito pools, which were molecularly screened for WNV presence. In this case, 14 environmental variables were associated with WNV detection in wild birds and mosquitos by using two separate MaxEnt models. Viral RNA was not detected in the target species during 2019, although in 2020, it was reported on 46 wild birds of ten species and 22 mosquito pools (Culex pipiens and Aedes albopictus). Altitude and land uses were significant predictors for both models and in fact, suitable conditions for virus occurrence were identified in low altitude zones. Bird- and mosquito-based surveillance systems yielded similar results and allowed for targeted vector control applications in cases of increased virus activity. Human cases were not reported on Peloponnese in 2020.

Bayesian time-varying occupancy model for West Nile virus in Ontario, Canada

Occupancy models determine the true presence or absence of a species by adjusting for imperfect detection in surveys. They often assume that species presences can be detected only if sites are occupied during a sampling season. We extended these models to estimate occupancy rates that vary throughout a sampling season as well as account for spatial dependence among sites. For these methods, we constructed a fast Gibbs sampler with the Pólya-Gamma augmentation strategy to conduct inference on covariate effects. We applied these methods to evaluate how environmental conditions and surveillance practices are associated with the presence of West Nile virus in mosquito traps across Ontario, Canada from 2002 to 2017. We found that urban land cover and warm temperatures drove viral occupancy, whereas viral testing on pools with higher proportions of Culex mosquitoes was more likely to result in a positive test for West Nile virus. Models with time-varying occupancy effects achieved much lower Watanabe-Akaike information criteria than models without such effects. Our final model had strong predictive performance on test data that included some of the most extreme seasons, demonstrating the promise of these methods in the study of pathogens spread by mosquito vectors.

Mapping the Risk for West Nile Virus Transmission, Africa.

West Nile virus (WNV) is an emergent arthropodborne virus that is transmitted from bird to bird by mosquitoes. Spillover events occur when infected mosquitoes bite mammals. We created a geopositioned database of WNV presence in Africa and considered reports of the virus in all animal components: reservoirs, vectors, and nonhuman dead-end hosts. We built various biogeographic models to determine which drivers explain the distribution of WNV throughout Africa. Wetlands of international importance for birds accounted for the detection of WNV in all animal components, whereas human-related drivers played a key role in the epizootic cases. We combined these models to obtain an integrative and large-scale perspective of the areas at risk for WNV spillover. Understanding which areas pose the highest risk would enable us to address the management of this spreading disease and to comprehend the translocation of WNV outside Africa through avian migration routes.

Intensive West Nile Virus Circulation in Serbia in 2018-Results of Integrated Surveillance Program.

The results of the Serbian national integrated West Nile virus (WNV) surveillance program conducted in 2018 and funded by the Serbian Veterinary Directorate are presented. The WNV surveillance program encompassed the entire territory of Serbia and was conducted by the veterinary service in collaboration with entomologists and ornithologists. The objective of the program was early detection of WNV circulation in the environment and timely reporting to the public health service and local authorities to increase clinical and mosquito control preparedness. The program was based on the detection of WNV presence in wild birds (natural hosts) and mosquitoes (virus vectors) and on serological testing of sentinel horses (WNV-specific IgM antibodies). The season 2018 was confirmed to be the season of the most intensive WNV circulation with the highest number and severity of human cases in Serbia ever reported. The most intense WNV circulation was observed in the northern and central parts of Serbia including Vojvodina Province, the Belgrade City area, and surrounding districts, where most positive samples were detected among sentinel animals, mosquitoes and wild birds. The majority of human cases were preceded by the detection of WNV circulation during the surveillance. The WNV surveillance program in 2018 showed satisfactory results in the capacity to indicate the spatial distribution of the risk for humans and sensitivity to early detection of WNV circulation in the environment.

West Nile Virus Seroprevalence in a Selected Donkey Population of Namibia

West Nile Virus (WNV) is a mosquito-borne virus enzootically maintained in birds. However, it can incidentally infect other species, leading to sometimes severe clinical consequences like in horses and especially human beings. Despite the topic relevance, the presence and distribution of WNV are currently unknown in Namibia. Several countries implement surveillance systems based on virus detection in birds, mosquitoes, and vertebrate species including horses. The present study aimed to fill this knowledge gap by serologically evaluating WNV exposure in Namibian donkeys, whose population is remarkably bigger than the horse one. Forty-seven out of 260 sampled animals showed neutralizing antibodies against WNV (18.07% [95% CI = 13.59–23.30%]), demonstrating its circulation in all country territory, although, with apparent regional differences. On the contrary, no association with animal age or sex could be identified. The present study demonstrates the widespread presence of WNV in Namibia as well as the practical utility and effectiveness of donkeys as sentinels for infection surveillance. Due to clinical relevance, vaccination campaigns should be considered for horses of high economic or genetic value. Additionally, the burden of WNV infection on human health should be carefully evaluated.