West Nile Virus Isolates Research Articles

Phylogenetic analysis and molecular genetic characteristics of West Nile virus lineage 2 isolates circulating in the Russian Federation.

Since its initial detection in Africa, the West Nile virus has disseminated widely across all continents, becoming endemic in numerous countries, including the Russian Federation. A substantial expansion of the West Nile virus range was observed in the European part of the Russian territory in 1999. In light of this epidemiological trend, research endeavours focusing on monitoring West Nile virus circulation activity in endemic regions of the country have gained paramount significance. A substantial dataset has been accrued from 2007 onwards regarding genomic variability and dissemination dynamics across the country throughout the entire monitoring period for the West Nile fever pathogen. The objective of this study was to characterise West Nile virus isolates that have been circulating in the Russian Federation and identify their molecular and genetic characteristics. A phylogenetic analysis of 55 complete genome sequences revealed that the West Nile virus population within the Russian Federation is genetically heterogeneous and is represented by four major clades. One of these clades is currently exhibiting extensive spread into new regions of the country.

The potential role of the Asian bush mosquito Aedes japonicus as spillover vector for West Nile virus in the Netherlands

BackgroundIn recent years the Asian bush mosquito Aedes japonicus has invaded Europe, including the Netherlands. This species is a known vector for a range of arboviruses, possibly including West Nile virus (WNV). As WNV emerged in the Netherlands in 2020, it is important to investigate the vectorial capacity of mosquito species present in the Netherlands to estimate the risk of future outbreaks and further spread of the virus. Therefore, this study evaluates the potential role of Ae. japonicus in WNV transmission and spillover from birds to dead-end hosts in the Netherlands.MethodsWe conducted human landing collections in allotment gardens (Lelystad, the Netherlands) in June, August and September 2021 to study the diurnal and seasonal host-seeking behaviour of Ae. japonicus. Furthermore, their host preference in relation to birds using live chicken-baited traps was investigated. Vector competence of field-collected Ae. japonicus mosquitoes for two isolates of WNV at two different temperatures was determined. Based on the data generated from these studies, we developed a Susceptible-Exposed-Infectious-Recovered (SEIR) model to calculate the risk of WNV spillover from birds to humans via Ae. japonicus, under the condition that the virus is introduced and circulates in an enzootic cycle in a given area.ResultsOur results show that Ae. japonicus mosquitoes are actively host seeking throughout the day, with peaks in activity in the morning and evening. Their abundance in August was higher than in June and September. For the host-preference experiment, we documented a small number of mosquitoes feeding on birds: only six blood-fed females were caught over 4 full days of sampling. Finally, our vector competence experiments with Ae. japonicus compared to its natural vector Culex pipiens showed a higher infection and transmission rate when infected with a local, Dutch, WNV isolate compared to a Greek isolate of the virus. Interestingly, we also found a small number of infected Cx. pipiens males with virus-positive leg and saliva samples.ConclusionsCombining the field and laboratory derived data, our model predicts that Ae. japonicus could act as a spillover vector for WNV and could be responsible for a high initial invasion risk of WNV when present in large numbers.Graphical

Study of the circulation and properties of the West Nile virus in Russia in 2022

Introduction. The relevance of the study is due to the need to assess the real expansion of West Nile fever (WNF) in Russia, analyze the manifestations of epizootic and epidemic processes and study the population structure of West Nile virus (WNV).
 Aim. To obtain objective data on the intensity of WNV circulation in certain territories of Russia and study the properties of the isolated strains of the pathogen.
 Materials and methods. 4564 samples of field material from 23 subjects of the Russian Federation and 1547 samples of clinical material from 12 subjects of the Russian Federation were examined. A set of laboratory diagnostic methods was used: ELISA, RT-PCR, virological, sequencing.
 Results. In 20 out of 1331 (1.5%) examined febrile patients, IgM antibodies to WNV were detected, including positive cases identified for the first time in the Karachay-Cherkess Republic, Tver and Vladimir regions. The presence of immunity to WNV was found on average in 8.6% of 11 federal subjects' population with high seroprevalence rates in Zaporozhye (24,5%), Tula (15,4%) and Kursk (11,1%) regions. Low-avidity IgG antibodies were detected in 44 (33,1%) samples from a population of 9 federal subjects. Intensive circulation of WNV lineage 2 in the epizootic cycle in the southern part of European Russia was confirmed. 12 WNV isolates were obtained, including those isolated for the first time in the Republic of Crimea, the Karachay-Cherkess Republic and the Stavropol Territory. The heterogeneity of circulating WNF causative agent's strains related to the two clades of the WNV lineage 2 formed in 2021 and 2022 was established.
 Conclusion. In the course of comprehensive monitoring studies, a new northern border of the WNF range was established, which as of 2022 passes through the territory of the Tver region. Data from seroepidemiological studies, including the detection of low-avidity IgG antibodies, confirm fairly intense, but undiagnosed contact of the population of the European part of Russia with the WNF pathogen. In the southern region of the European part of Russia, WNV genotype 2 predominantly circulates, belonging to at least two clades formed in 2021 and 2022.

Fatal West Nile Virus Infection in Horse Returning to United Kingdom from Spain, 2022.

We report fatal West Nile virus (WNV) infection in a 7-year-old mare returning to the United Kingdom from Spain. Case timeline and clustering of virus sequence with recent WNV isolates suggest that transmission occurred in Andalusía, Spain. Our findings highlight the importance of vaccination for horses traveling to WNV-endemic regions.

West Nile fever as a relevant health hazard: The history of studying measures of and its prevention in Russia

The review generalizes data on West Nile fever manifestations in Russian between 1963 and 2022. Researchers have deter-mined peculiarities of the endemic process typical for this arboviral infection: cyclic rises in incidence with an interval of 1 to 8 years; the disease cases being predominantly registered in the south of the European part of the country; elevated risks of the disease for people aged 60 years and older; most West Nile fever cases without affecting the central nervous system with a continuous steady increase in the share of neuroinvasive forms. There are ongoing discussions of a considerable growth in an area where West Nile fever spreads as the incidence of the disease has been registered in Central Russia and this calls for assessment studies aimed at determining the northern borders of the infection area. The reviewed studies also systematize data on the WNV carriers and vectors and highlight the necessity to conduct large-scale experimental studies with their focus on examining susceptibility of various species of vertebrates and arthropods to the West Nile virus and assessing the efficiency of its transmission. The West Nile virus population that circulates in Russia has been shown to be heterogeneous and represented by the genotypes 1, 2, and 4, of which the genotype 2 is prevailing at present. The review also provides the findings of our own research with its focus on the genomes of the West Nile virus isolates indicating circulation of various genetic variants of the pathogen belonging to the genotype 2. The reviewed studies consider issues related to establishing epidemiological surveillance and sanitary-anti-epidemic (preventive) measures regarding West Nile fever in Russia and the principles of their organization at the present stage.

West Nile virus infections in Hungary: Epidemiological update and phylogenetic analysis of the Hungarian virus strains between 2015 and 2022.

Following the introduction of the West Nile virus (WNV) into Hungary in 2004, it has shortly become one of the most important human arbovirus infections, with a gradually increasing number of cases. The study aimed to summarize the current epidemiological situation in Hungary and sequence the WNV PCR-positive clinical specimens and virus isolates by next-generation whole genome sequencing (NGS) to obtain a detailed phylogenetic analysis of the circulating virus strains. Whole blood and urine samples from confirmed WNV-infected patients and WNV isolates were investigated by reverse transcription PCR assays. Genome sequencing was carried out by Sanger-method, followed by NGS on the Illumina MiSeq platform. Altogether 499 human infections were diagnosed between 2004 and 2022. A particularly remarkable increase in human WNV infections was observed in 2018, while the number of reported cases significantly decreased during the COVID-19 pandemic. Between 2015 and 2022, 15WNV isolates, and 10 PCR-positive clinical specimens were investigated by NGS. Phylogenetic analysis revealed that the major European WNV lineage 2 clades, namely the Eastern European (or Russian) and the Central European (or Hungarian) clades, are presented in Hungary. Strains of the Balkan and other European clusters within the Central European clade are co-circulating in the country, following a characteristic geographical distribution. In Hungary, the presence and co-circulation of multiple lineage 2 WNV strains could be identified in the last few years. Therefore, in light of the 2018WNV outbreak, sequence-based typing of the currently circulating strains could highly support outbreak investigations.

West Nile Fever in the Russian Federation in 2022, the Incidence Forecast for 2023

The review presents an analysis of West Nile fever (WNF) epidemiological situation in the Russian Federation in 2022 and the summarized results of monitoring over the pathogen. The following features of the WNF epidemic process in Russia are outlined: the decrease (by 4 times) in the incidence rates compared to the long-term average values against an extremely extensive nature of manifestations (16 constituent entities in 6 federal districts), including the detection of local cases in 5 new territories (Tver, Tambov, Vladimir Regions, Khanty-Mansi Autonomous District, and Karachay-Cherkess Republic), predominant registration of incidence in the Central Federal District (51 %), early start and termination of the epidemic season. There is a decrease in the proportion of neuroinvasive forms in the structure of incidence, prevalence of females and the age group of “60 years and over”, as well as record rate values of people infected at the place of residence in cities, which is associated with the peculiarities of case detection, namely, screening examinations of febrile patients in hospitals by efforts of the Reference Center, according to the results of which 60 % of all registered patients with WNF in Russia were diagnosed. Monitoring studies of the Reference Center in the territory of the Central, Southern and North-Caucasian Federal Districts confirmed the intensive circulation of the pathogen. The low level of officially registered incidence is caused by insufficiently effective identification of patients. Molecular genetic studies have shown that West Nile virus lineage 2 circulated in the European part of Russia, both in epizootic and epidemic cycles. Phylogenetic analysis has revealed that 4 West Nile virus isolates found in Astrakhan, Volgograd Regions, the Republic of Kalmykia and Stavropol Territory in 2022 belong to a new genovariant of the genotype 2, first identified in Russia in 2021. Possible complication of the epidemiological situation in all federal districts of the center and south of the European part of Russia is predicted.

First Isolation and Genome Sequence Analysis of West Nile Virus in Mosquitoes in Brazil.

West Nile virus is a flavivirus transmitted by mosquitoes, mainly of the genus Culex. In Brazil, serological studies have already indicated the circulation of the virus since 2003, with the first human case detected in 2014. The objective of the present paper is to report the first isolation of WNV in a Culex (Melanoconion) mosquito. Arthropods were collected by protected human attraction and CDC light bait, and taxonomically identified and analyzed by viral isolation, complement fixation and genomic sequencing tests. WNV was isolated from samples of Culex (Melanoconion) mosquitoes, and the sequencing analysis demonstrated that the isolated strain belonged to lineage 1a. The finding of the present study presents the first evidence of the isolation and genome sequencing of WNV in arthropods in Brazil.

Immunization with Usutu virus and with a chimeric West Nile virus (WNV) harboring Usutu-E protein protects immunocompetent adult mice against lethal challenges with different WNV lineage 1 and 2 strains

West Nile virus (WNV) and Usutu virus (USUV), two antigenically related flaviviruses co-circulating in Europe, can cause severe neurological disease in animals and humans. The immune response against USUV and WNV and their immunopathogenesis are still poorly investigated. Here we present results upon sequential infections of adult immunocompetent CD-1 and BALB/c mice primed with two different doses (high dose, HD or low dose, LD) of an USUV isolate and challenged with HD or LD of three different WNV isolates. CD-1 and BALB/c LD USUV-primed mice, regardless of the dose, are largely protected from lethal WNV challenges despite showing no detectable neutralizing antibodies. Furthermore, mice immunized with a chimeric virus harboring the E protein of USUV within the WNV backbone (WNVE-USUV) are protected against a lethal challenge with WNV. We believe these findings could contribute to understanding the dynamics of the interaction during sequential infection of these two flaviviruses.

Detection of West Nile virus isolates in poultry in central Vietnam in 2015-2019

Cases of detection of RNA or ELISA markers of West Nile virus (WNV) have been recorded in many countries of Southeast Asia. At the same time, there were no reports of outbreaks of fevers caused by WNV. Perhaps this is due to the asymptomatic or very mild course of the disease or to the focus of the health systems of these countries on other viral fevers. In this work, for the first time in Vietnam, West Nile virus (WNV) RNA was detected in poultry. WNV RNA was found in three lung samples of chickens from Nghe An province collected in 2017. The isolates belonged to lineages 1a and 2, responsible for many WNV outbreaks in Europe and North America and therefore require close attention.

West Nile Virus in Common Wild Avian Species in Israel.

In order to evaluate the contribution of different wild bird species to West Nile virus (WNV) circulation in Israel, during the months preceding the 2018 outbreak that occurred in Israel, we randomly sampled 136 frozen carcasses of a variety of avian species. Visceral and central nervous system (CNS) tissue pools were tested using WNV NS2A RT qPCR assay; of those, 15 (11.03%, 95% CI: 6.31–17.54%) tissue pools were positive. A total of 13 out of 15 WNV RT qPCR positive samples were successfully sequenced. Phylogenetic analysis indicated that all WNV isolates were identified as lineage 1 and all categorized as cluster 2 eastern European. Our results indicated that WNV isolates that circulated within the surveyed wild birds in spring 2018 were closely related to several of the isolates of the previously reported 2018 outbreak in birds in Israel and that the majority of infected birds were of local species.

Pathogenesis of Two Western Mediterranean West Nile Virus Lineage 1 Isolates in Experimentally Infected Red-Legged Partridges (Alectoris rufa).

West Nile virus (WNV) is the most widespread flavivirus in the world with a wide vertebrate host range. Its geographic expansion and activity continue to increase with important human and equine outbreaks and local bird mortality. In a previous experiment, we demonstrated the susceptibility of 7-week-old red-legged partridges (Alectoris rufa) to Mediterranean WNV isolates Morocco/2003 and Spain/2007, which varied in virulence for this gallinaceous species. Here we study the pathogenesis of the infection with these two strains to explain the different course of infection and mortality. Day six post-inoculation was critical in the course of infection, with the highest viral load in tissues, the most widespread virus antigen, and more severe lesions. The most affected organs were the heart, liver, and spleen. Comparing infections with Morocco/2003 and Spain/2007, differences were observed in the viral load, virus antigen distribution, and lesion nature and severity. A more acute and marked inflammatory reaction (characterized by participation of microglia and CD3+ T cells) as well as neuronal necrosis in the brain were observed in partridges infected with Morocco/2003 as compared to those infected with Spain/2007. This suggests a higher neurovirulence of Morocco/2003, probably related to one or more specific molecular determinants of virulence different from Spain/2007.

Peculiarities of Epidemiological Situation on the West Nile Fever in the Russian Federation in 2020 and Forecast for Its Development in 2021

The paper presents an analysis of West Nile Fever incidence in the Russian Federation in 2020, summarizes the results and identifies problematic issues of the pathogen monitoring. Manifestations of West Nile Fever in 2020 were characterized by a low incidence rate (10 times lower than the average long-term value) with sporadic cases registration in the endemic areas of the Southern (9 cases) and Central (1 case) Federal Districts. A discrepancy between the morbidity structure (distribution by age, sex, social status) and the trends that have developed in Russia in recent years is shown. The analysis of officially recorded cases doesn’t characterize the epidemic process of West Nile fever in Russia during 2020-season as a whole. The generalized results of monitoring of the West Nile virus circulation in environmental objects in 2020 indicate a decrease in the effectiveness of its implementation and a low detectability of pathogen markers. A decrease in the volume of diagnostic studies for the active detection of patients with West Nile fever in the epidemic season (5.7 times lower compared to 2019), as well as serological screening of healthy population samples (1.6 times) has been established. The results of a molecular-genetic study of the pathogen showed that lineage 2 of the pathogen was circulating in the European part of Russia. The circulation of the lineage 4 of the virus in the enzootic cycle in the Republic of Kalmykia was found out. The genome sequences of 11 West Nile virus isolates allocated in 2019 and 2020 were obtained. Phylogenetic analysis revealed that all isolates allocated in the Volgograd Region and isolates from the Rostov and Astrakhan regions belong to the Volgograd clade of the lineage 2 of the West Nile virus. Based on the assessment of abiotic and biotic factors, possible local increases in the incidence of West Nile fever in 2021 in the regions of the Southern and North Caucasian Federal Districts and in the south of Western Siberia have been substantiated.

Recovery and Genetic Characterization of a West Nile Virus Isolate from China.

West Nile virus (WNV) is an important neurotropic flavivirus that is widely distributed globally. WNV strain XJ11129 was first isolated in Xinjiang, China, and its genetic and biological characteristics remain largely unknown. In this study, phylogenetic and sequence analyses revealed that XJ11129 belongs to lineage 1a and shares high genetic identity with the highly pathogenic strain NY99. Then, the full-length genomic cDNA of XJ11129 was amplified and assembled using a modified Gibson assembly (GA) method. The virus (named rXJ11129) was successfully rescued in days following this method. Compared with other wild-type WNV isolates, rXJ11129 exhibited virulence indistinguishable from that of the NY99 strain in vivo. In summary, the genomic and virulence phenotypes of rXJ11129 were characterized in vivo and in vitro, and these data will improve the understanding of the spread and pathogenesis of this reemerging virus.

Evidence of West Nile virus infection in migratory and resident wild birds in west coast of peninsular Malaysia

West Nile virus (WNV) is a zoonotic mosquito-borne flavivirus that is harbored and amplified by wild birds via the enzootic transmission cycle. Wide range of hosts are found to be susceptible to WNV infection including mammals, amphibians and reptiles across the world. Several studies have demonstrated that WNV was present in the Malaysian Orang Asli and captive birds. However, no data are available on the WNV prevalence in wild birds found in Malaysia. Therefore this study was conducted to determine the serological and molecular prevalence of WNV in wild birds in selected areas in the West Coast of Peninsular Malaysia. Two types of wild birds were screened, namely migratory and resident birds in order to explore any possibility of WNV transmission from the migratory birds to the resident birds. Thus, a cross-sectional study was conducted at the migratory birds sanctuary located in Kuala Gula, Perak and Kapar, Selangor by catching 163 migratory birds, and 97 resident birds from Kuala Gula and Parit Buntar, Perak at different time between 2016 and 2017 (Total, n = 260). Blood and oropharyngeal swabs were collected for serological and molecular analysis, respectively. Serum were screened for WNV antibodies using a commercial competitive ELISA (c-ELISA) (ID Screen® West Nile Competition Multi-species ELISA, ID VET, Montpellier, France) and cross-reactivity towards Japanese Encephalitis virus (JEV) was also carried out using the JEV-double antigen sandwich (DAS) ELISA. Oropharyngeal swabs were subjected to one-step RT-PCR to detect WNV RNA, in which positive reactions were subsequently sequenced. WNV seropositive rate of 18.71% (29/155) at 95% CI (0.131 to 0.260) and molecular prevalence of 15.2% (16/105) at 95% CI (0.092 to 0.239) were demonstrated in migratory and resident wild birds found in West Coast Malaysia. Phylogenetic analyses of the 16 WNV isolates found in this study revealed that the local strains have 99% similarity to the strains from South Africa and were clustered under lineage 2. Evidence of WNV infection in resident and migratory birds were demonstrated in this study. As a summary, intervention between migratory birds, resident birds and mosquitoes might cause the introduction and maintenance of WNV in Malaysia, however the assumption could be further proven by studying the infection dynamics in the mosquitoes present in the studied areas.

N-linked glycosylation of the West Nile virus envelope protein is not a requisite for avian virulence or vector competence.

The N-linked glycosylation motif at amino acid position 154–156 of the envelope (E) protein of West Nile virus (WNV) is linked to enhanced murine neuroinvasiveness, avian pathogenicity and vector competence. Naturally occurring isolates with altered E protein glycosylation patterns have been observed in WNV isolates; however, the specific effects of these polymorphisms on avian host pathogenesis and vector competence have not been investigated before. In the present study, amino acid polymorphisms, NYT, NYP, NYF, SYP, SYS, KYS and deletion (A’DEL), were reverse engineered into a parental WNV (NYS) cDNA infectious clone to generate WNV glycosylation mutant viruses. These WNV glycosylation mutant viruses were characterized for in vitro growth, pH-sensitivity, temperature-sensitivity and host competence in American crows (AMCR), house sparrows (HOSP) and Culex quinquefasciatus. The NYS and NYT glycosylated viruses showed higher viral replication, and lower pH and temperature sensitivity than NYP, NYF, SYP, SYS, KYS and A’DEL viruses in vitro. Interestingly, in vivo results demonstrated asymmetric effects in avian and mosquito competence that were independent of the E-protein glycosylation status. In AMCRs and HOSPs, all viruses showed comparable viremias with the exception of NYP and KYS viruses that showed attenuated phenotypes. Only NYP showed reduced vector competence in both Cx. quinquefasciatus and Cx. tarsalis. Glycosylated NYT exhibited similar avian virulence properties as NYS, but resulted in higher mosquito oral infectivity than glycosylated NYS and nonglycosylated, NYP, NYF, SYP and KYS mutants. These data demonstrated that amino acid polymorphisms at E154/156 dictate differential avian host and vector competence phenotypes independent of E-protein glycosylation status.

Comparative fitness of West Nile virus isolated during California epidemics.

West Nile virus (WNV) has been circulating in California since its first detection in 2003, causing repeated outbreaks affecting public, wildlife and veterinary health. Epidemics of WNV are difficult to predict due to the multitude of factors influencing transmission dynamics among avian and mosquito hosts. Typically, high levels of WNV amplification are required for outbreaks to occur, and therefore associated viral strains may exhibit enhanced virulence and mortality in competent bird species resulting in increased mosquito infection prevalence. In our previous study, most WNV isolates made from California during 2007–08 showed increased fitness when competed in House Finches (HOFI, Haemorhous mexicanus) and Culex tarsalis Coquillett mosquitoes against COAV997-5nt, a genetically marked recombinant virus derived from a 2003 California strain. Herein, we evaluated the competitive fitness of WNV strains isolated during California epidemics in 2004, 2005, 2007, 2011 and 2012 against COAV997-5nt. These outbreak isolates did not produce elevated mortality in HOFIs, but replicated more efficiently than did COAV997-5nt based on quantification of WNV RNA copies in sera, thereby demonstrating increased competitive fitness. Oral co-infections in Cx. tarsalis resulted in similar virus-specific infection and transmission rates, indicating that outbreak isolates did not have a fitness advantage over COAV997-5nt. Collectively, WNV isolates from outbreaks demonstrated relatively greater avian, but not vector, replicative fitness compared to COAV997-5nt, similar to previously characterized non-outbreak isolates of WNV. Our results indicated that ecological rather than viral factors may facilitate WNV amplification to outbreak levels, but monitoring viral phenotypes through competitive fitness studies may provide insight into altered replication and transmission potential among emerging WNV strains.

First isolation of West Nile virus in Brazil.

BACKGROUNDSerological evidence of West Nile virus (WNV) infection has been reported in different regions of Brazil from equine and human hosts but the virus had never been isolated in the country.OBJECTIVES We sought to identify the viral etiology of equine encephalitis in Espírito Santo state.METHODS We performed viral culture in C6/36 cells, molecular detection of WNV genome, histopathology and immunohistochemistry from horse cerebral tissue. We also carried out sequencing, phylogenetic analysis and molecular clock.FINDINGS Histopathologic analysis from horse cerebral tissue showed injury related to encephalitis and WNV infection was confirmed by immunohistochemistry. The virus was detected by reverse transcription quantitative polymerase chain reaction (RT-qPCR) from brain tissue and subsequently isolated in C6/36 cells. WNV full-length genome was sequenced showing the isolated strain belongs to lineage 1a. The molecular clock indicated that Brazilian WNV strain share the same common ancestor that were circulating in US during 2002-2005.MAIN CONCLUSIONS Here we report the first isolation of WNV in Brazil from a horse with neurologic disease, which was clustered into lineage 1a with others US WNV strains isolated in beginning of 2000’s decade.

A monoclonal antibody to DIII E protein allowing the differentiation of West Nile virus from other flaviviruses by a lateral flow assay

West Nile Virus (WNV) belongs to the Flaviviridae family, genus Flavivirus, which includes other emerging arthropod-borne viruses (arboviruses) pathogenic for animals and/or humans. West Nile Virus is a genetically diverse RNA virus with at least 7 different recognized lineages. Following its recent introduction and subsequent expansion to the Americas, WNV is currently one of the most widely spread arboviruses in the world having recently re-emerged in the Mediterranean basin, Central and Eastern Europe. Laboratory tests are essential to confirm WNV infection and monoclonal antibodies represent useful tools for the development of diagnostic assays. A monoclonal antibody, 1D11, recognizing an epitope in the domain III of the envelope glycoprotein of WNV, was selected for this study. Its suitability to detect a range of WNV variants representative of its whole genetic range, and to differentiate it from other flaviviruses and arboviruses, was assessed by means of an immunochromatographic assay in an LFA format. A panel of cell culture supernatants infected with 9 different WNV isolates representing a wide range of genetic lineages, and 16 non-WNV arboviruses, including flaviviruses closely related to WNV, were tested. The mAb correctly detected all WNV strains, and did not react with any of the non-WNV arboviruses.

Susceptibility and role as competent host of the red-legged partridge after infection with lineage 1 and 2 West Nile virus isolates of Mediterranean and Central European origin

West Nile virus (WNV; genus Flavivirus; family Flaviviridae) is the aetiological agent of an emerging, mosquito-borne disease with great impact on human and animal health. Over the past 15 years, WNV has been responsible for large epidemics mainly in North America but also in Europe, where lineage 1 and more recently lineage 2 strains have caused an upsurge in the number of outbreaks with increased human infection and higher virulence for certain wild bird species. This study aimed to compare the course of infection of the lineage 1 WNV strains Israel/98 and Italy/08 and the lineage 2 strain Austria/08 in the red-legged partridge (Alectoris rufa), a gallinaceous bird indigenous to the Iberian Peninsula and widely distributed in Southern and Western Europe. After experimental inoculation, clinical and analytic parameters (viraemia, viral load, antibodies) were examined over a period of 15 days. All inoculated birds became viremic and showed clinical disease, with a morbidity rate of 100% and mortality rates between 22.2 and 55.5% depending on the virus strain. The red-legged partridge demonstrated to be a competent host for transmission of the three investigated WNV isolates with the highest competence index observed for the Italian strain. Likewise, this strain was the most pathogenic causing the highest viral loads in blood, organs, feathers and oral and cloacal secretions. These experimental results indicate that the red-legged partridge is highly susceptible to the infection with lineage 1 and 2 WNV strains and that this species may act as an amplifying host for both WNV lineages.