West Nile Virus (WNV) is a mosquito-borne virus that affects horses, causing neurological disease. It is transmitted primarily through the bite of infected mosquitoes, which acquire the virus from feeding on infected birds. Horses are considered a dead-end host, meaning they do not contribute to the transmission cycle of the virus. Clinical signs in horses can range from mild fever and lethargy to severe neurological symptoms such as ataxia, weakness, and paralysis. Diagnosis is typically confirmed through serological testing or detection of the virus in tissues. Vaccination is available and serves as a preventive measure to reduce the incidence of the disease. This page compiles peer-reviewed research studies and scholarly articles that explore the epidemiology, pathogenesis, clinical presentation, and management of West Nile Virus in equine populations.
Read AJ, Finlaison DS, Gu X, Hick PM, Moloney BJ, Wright T, Kirkland PD.Between February and June 2011, more than 300 horses with unexplained neurological disease were observed in New South Wales, Australia. A virulent strain of West Nile virus (WNV ), of Australian origin, was shown to be the cause of many of these cases. Methods: We reviewed the clinical descriptions provided by veterinary practitioners and the associated laboratory results. Although there was a range of clinical signs described, ataxia was the only sign that was consistently described in laboratory-confirmed cases. Results: WNV was detected in brain samples by real-time reverse transcription PC...
Young JJ, Coulombier D, Domanović D, Zeller H, Gossner CM.West Nile virus (WNV) infection is notifiable in humans and equids in the European Union (EU). An area where a human case is detected is considered affected until the end of the mosquito transmission season (week 48) and blood safety measures have to be implemented. We used human and equine case notifications between 2013 and 2017 to define the WNV distribution in the EU and to investigate the relevance of using equine cases as a complementary trigger for blood safety measures. Adding areas with equine cases to the definition of an affected area would have a major impact on blood safety measur...
Stejskalova K, Cvanova M, Oppelt J, Janova E, Horecky C, Horecka E, Knoll A, Leblond A, Horin P.West Nile virus (WNV) is a mosquito-borne zoonotic neurotropic virus capable to cause lethal meningoencephalitis (WNE) in infected hosts such as birds, horses, and humans. Due to their sensitivity, horses serve as sentinel species in areas at risk. We studied a population of Camargue horses living in Southern France in two zones with endemic WNV circulation where WNV outbreaks were recorded in 2000 and 2003-4. Two sets of microsatellite markers located in MHC and Ly49 genomic regions were genotyped as well as multiple SNPs in ten immunity-related candidate gene regions. Associations between ge...
To evaluate the immunological response following vaccination, 40 WNV serologically negative horses were selected and divided in two groups of 20 animals. One group was vaccinated (booster after 28 days) with a whole inactivated viral strain and the second group with a live recombinant canarypox virus expressing the genes coding for the WNV preM/E viral proteins. IgM, IgG and neutralizing antibodies were monitored by class specific ELISAs and serum neutralization assay for 360 days. In both groups, IgM antibodies were first detected 7 days post vaccination (dpv). However, in the group vaccinate...
Cazeau G, Leblond A, Sala C, Froustey M, Beck C, Lecollinet S, Tapprest J.Few studies about the use of quantitative equine mortality data for monitoring purposes are available. Our study evaluated the utility of monitoring emerging equine diseases using mortality data collected by rendering plants. We used approaches involving modelling of historical mortality fluctuations and detection algorithm methods to analyse changes in equine mortality in connection with the West Nile Virus (WNV) outbreak that occurred between July and September 2015 along the Mediterranean coast of France. Two weeks after the first equine WNV case was detected by clinical surveillance, detec...
Martins LC, Silva EVPD, Casseb LMN, Silva SPD, Cruz ACR, Pantoja JAS, Medeiros DBA, Martins Filho AJ, Cruz EDRMD, Araújo MTF, Cardoso JF....Serological 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. Objective: 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. Results: Histopathologic analysis from horse cerebral tissue showed injury related...
Prakoso D, Dark MJ, Barbet AF, Salemi M, Barr KL, Liu JJ, Wenzlow N, Waltzek TB, Long MT.West Nile virus (WNV), a small, positive sense, single stranded RNA virus continues to encroach into new locales with emergence of new viral variants. Neurological disease in the equine can be moderate to severe in the face of low to undetectable virus loads. Physical methods of virus enrichment may increase sensitivity of virus detection and enhance analysis of viral diversity, especially for deep sequencing studies. However, the use of these techniques is limited mainly to non-neural tissues. We investigated the hypothesis that elimination of equine brain RNA enhances viral detection without...
Hedell R, Andersson MG, Faverjon C, Marcillaud-Pitel C, Leblond A, Mostad P.A potentially sensitive way to detect disease outbreaks is syndromic surveillance, i.e. monitoring the number of syndromes reported in the population of interest, comparing it to the baseline rate, and drawing conclusions about outbreaks using statistical methods. A decision maker may use the results to take disease control actions or to initiate enhanced epidemiological investigations. In addition to the total count of syndromes there are often additional pieces of information to consider when assessing the probability of an outbreak. This includes clustering of syndromes in space and time as...
Hemida MG, Perera RAPM, Chu DKW, Ko RLW, Alnaeem AA, Peiris M.West Nile virus (WNV) is an important emerging zoonotic arbovirus giving rise to clinical syndromes of varying severity in humans and horses. Culex mosquitoes are the main vector. Although WNV has been reported in many countries in the Middle East and Asia, little is known about its prevalence in equine populations in the Arabian Peninsula. We have carried out a serological study on 200 horses to assess WNV infection in the Eastern and Central regions of Saudi Arabia in 2013-2015. Sera were tested for the presence of WNV antibodies in parallel using a commercial enzyme-linked immunosorbent ass...
Silva ASG, Matos ACD, da Cunha MACR, Rehfeld IS, Galinari GCF, Marcelino SAC, Saraiva LHG, Martins NRDS, Maranhão RPA, Lobato ZIP, Pierezan F....Mosquito-borne arboviruses are a major public health concern worldwide and are responsible for emerging and re-emerging diseases. Taken together, the arboviruses have a strong impact on public health and are the most common causes of equine encephalitis. In-depth diagnostic investigation of equine viral encephalitis is of utmost importance for the epidemiological surveillance and control of this disease. Regarding neurological disorders in equids, in April-May 2018, at least 12 cases of equid mortality with acute neurological signs were reported in six farms from Espirito Santo state, Brazil. ...
Rebollo B, Sarraseca J, Lecollinet S, Abouchoaib N, Alonso J, García-Bocanegra I, Sanz AJ, Venteo Á, Jiménez-Clavero MA.West Nile virus (WNV) is a zoonotic arboviral pathogen affecting humans, birds, and horses. Vaccines are available for veterinary use, which efficiently prevent the infection in horses. Most common diagnostic tools rely on the identification of the agent (RT-PCR, virus isolation), or on the detection of antibodies (IgM and IgG) recognizing structural proteins of the virus or neutralizing virus infection in cell cultures (virus-neutralization tests). The recent emergence of WNV in different parts of the world has resulted in an increase in the vaccination of horses in many countries. Methods fo...
Kumar B, Manuja A, Gulati BR, Virmani N, Tripathi BN.Zoonotic diseases are the infectious diseases that can be transmitted to human beings and vice versa from animals either directly or indirectly. These diseases can be caused by a range of organisms including bacteria, parasites, viruses and fungi. Viral diseases are highly infectious and capable of causing pandemics as evidenced by outbreaks of diseases like Ebola, Middle East Respiratory Syndrome, West Nile, SARS-Corona, Nipah, Hendra, Avian influenza and Swine influenza. Unassigned: Many viruses affecting equines are also important human pathogens. Diseases like Eastern equine encephalitis (...
Chapman GE, Baylis M, Archer DC.Increased globalisation and climate change have led to concern about the increasing risk of arthropod-borne virus (arbovirus) outbreaks globally. An outbreak of equine arboviral disease in northern Europe could impact significantly on equine welfare, and result in economic losses. Early identification of arboviral disease by horse owners may help limit disease spread. In order to determine what horse owners understand about arboviral diseases of horses and their vectors, the authors undertook an open, cross-sectional online survey of UK horse owners. The questionnaire was distributed using soc...
Fortuna PRJ, Bielefeldt-Ohmann H, Ovchinnikov DA, Wolvetang EJ, Whitworth DJ.Horses are susceptible to a number of neurotropic viruses, including West Nile virus (WNV), which is a pathogen of global significance in both horses and humans. However, there are no in vitro models with which to study infectious neuropathic diseases in the horse. In an effort to redress this, we have generated neurons from equine induced pluripotent stem cells (equiPSCs) that express a range of cortical neuron-specific markers, in addition to the membrane-bound ligand ephrin B3, which plays an important role in axon guidance as well as functioning as the receptor through which henipaviruses,...
Chapman GE, Baylis M, Archer D, Daly JM.Equine populations worldwide are at increasing risk of infection by viruses transmitted by biting arthropods, including mosquitoes, biting midges (Culicoides), sandflies and ticks. These include the flaviviruses (Japanese encephalitis, West Nile and Murray Valley encephalitis), alphaviruses (eastern, western and Venezuelan encephalitis) and the orbiviruses (African horse sickness and equine encephalosis). This review provides an overview of the challenges faced in the surveillance, prevention and control of the major equine arboviruses, particularly in the context of these viruses emerging in ...
López-Ruiz N, Montaño-Remacha MDC, Durán-Pla E, Pérez-Ruiz M, Navarro-Marí JM, Salamanca-Rivera C, Miranda B, Oyonarte-Gómez S....In Andalusia, Spain, West Nile virus (WNV) surveillance takes place from April to November, during the active vector period. Within this area seroconversion to this virus was evidenced in wild birds in 2004, affecting horses and two humans for the first time in 2010. Since 2010, the virus has been isolated every year in horses, and national and regional surveillance plans have been updated with the epidemiological changes found. WNV is spreading rapidly throughout southern Europe and has caused outbreaks in humans. Here we describe the second WNV outbreak in humans in Andalusia, with three con...
Ahlers LRH, Goodman AG.Vector-borne diseases, including arboviruses, pose a serious threat to public health worldwide. Arboviruses of the flavivirus genus, such as Zika virus (ZIKV), dengue virus, yellow fever virus (YFV), and West Nile virus (WNV), are transmitted to humans from insect vectors and can cause serious disease. In 2017, over 2,000 reported cases of WNV virus infection occurred in the United States, with two-thirds of cases classified as neuroinvasive. WNV transmission cycles through two different animal populations: birds and mosquitoes. Mammals, particularly humans and horses, can become infected thro...
Bażanów B, Jansen van Vuren P, Szymański P, Stygar D, Frącka A, Twardoń J, Kozdrowski R, Pawęska JT.West Nile virus (WNV) and Usutu virus (USUV) are members of the family Flaviviridae which, natural life cycles involve mosquito-bird-mosquito transmission. Both represent emerging viruses in Europe with potential to cause neuroinvasive disease in humans. This study investigates the seroprevalence of serum neutralizing antibodies to WNV and to USUV in birds and in horses in Poland. Antibodies against WNV and USUV were detected in 5 (35.7%) and in 1 (7.14%) of 14 birds and in 62 (15.08%) and in 115 (27.98%) of 411 horses, respectively. Twenty-one WNV serologically positive horses (33.87%) and 67...
Csank T, Drzewnioková P, Korytár Ľ, Major P, Gyuranecz M, Pistl J, Bakonyi T.In central Europe, at least three flaviviruses circulate among vectors and vertebrate hosts. West Nile virus (WNV) and Usutu virus (USUV) are mosquito-borne viruses maintained in the nature by enzootic cycle between mosquitoes and birds. Tick-borne encephalitis virus (TBEV) is a flavivirus causing annual human cases in Slovakia. The aim of this study is the prevalence assessment of flavivirus infections in horses (n = 145) and birds (n = 109) by enzyme-linked immunosorbent assay (ELISA) and confirmation by neutralization test (VNT). WNV antibodies have been detected in 11.7% of tested ...
Kumar R, Patil RD.The importance of horse (Equus caballus) to equine practitioners and researchers cannot be ignored. An unevenly distributed population of equids harbors numerous diseases, which can affect horses of any age and breed. Among these, the affections of nervous system are potent reason for death and euthanasia in equids. Many episodes associated with the emergence of equine encephalitic conditions have also pose a threat to human population as well, which signifies their pathogenic zoonotic potential. Intensification of most of the arboviruses is associated with sophisticated interaction between ve...
Venter M, Pretorius M, Fuller JA, Botha E, Rakgotho M, Stivaktas V, Weyer C, Romito M, Williams J.During 2008-2015 in South Africa, we conducted West Nile virus surveillance in 1,407 animals with neurologic disease and identified mostly lineage 2 cases in horses (7.4%, 79/1,069), livestock (1.5%, 2/132), and wildlife (0.5%, 1/206); 35% were fatal. Geographic correlation of horse cases with seropositive veterinarians suggests disease in horses can predict risk in humans.
Barros SC, Ramos F, Fagulha T, Duarte M, Henriques AM, Waap H, Luís T, Costa T, Amador R, Quintans S, Fevereiro M.West Nile fever (WNF) is an emergent disease in Europe, under surveillance in the European Union. Following a 5-year period of apparent silence (autumn 2010 to summer 2015), West Nile virus (WNV) reemerged in the South of Portugal, in July 2015. Here we present data from the onset, geographic location within mainland Portugal, and outcome of clinical cases of WNV infection in horses in 2015 and 2016. During the transmission seasons of 2015 and 2016, twenty-seven horses, most symptomatic (n=20) were found positive to IgM, pr-E immunoglobulins and VNT, leading to the subsequent report to Animal ...
Piyasena TBH, Setoh YX, Hobson-Peters J, Prow NA, Bielefeldt-Ohmann H, Khromykh AA, Perera D, Cardosa MJ, Kirkland PD, Hall RA.In Australia, infection of horses with the West Nile virus (WNV) or Murray Valley encephalitis virus (MVEV) occasionally results in severe neurological disease that cannot be clinically differentiated. Confirmatory serological tests to detect antibody specific for MVEV or WNV in horses are often hampered by cross-reactive antibodies induced to conserved epitopes on the envelope (E) protein. This study utilized bacterially expressed recombinant antigens derived from domain III of the E protein (rE-DIII) of MVEV and WNV, respectively, to determine whether these subunit antigens provided specific...
García-Bocanegra I, Belkhiria J, Napp S, Cano-Terriza D, Jiménez-Ruiz S, Martínez-López B.During the last decade, West Nile virus (WNV) outbreaks have increased sharply in both horses and human in Europe. The aims of this study were to evaluate characteristics and spatio-temporal distribution of WNV outbreaks in horses in Spain between 2010 and 2016 in order to identify the environmental variables most associated with WNV occurrence and to generate high-resolution WNV suitability maps to inform risk-based surveillance strategies in this country. Between August 2010 and November 2016, a total of 403 WNV suspected cases were investigated, of which, 177 (43.9%) were laboratory confirm...
Rocheleau JP, Michel P, Lindsay LR, Drebot M, Dibernardo A, Ogden NH, Fortin A, Arsenault J.Periodic outbreaks of West Nile virus (WNV), Eastern equine encephalitis virus (EEEV) and to a lesser extent, California serogroup viruses (CSGV), have been reported in parts of Canada in the last decade. This study was designed to provide a broad assessment of arboviral activity in Quebec, Canada, by conducting serological surveys for these arboviruses in 196 horses, 1442 dogs and 485 humans. Sera were screened by a competitive enzyme linked immunosorbent assay and positive samples confirmed by plaque reduction neutralisation tests. The percentage of seropositive samples was 83·7%, 16·5%, 7...
Beck C, Lowenski S, Durand B, Bahuon C, Zientara S, Lecollinet S.West Nile Fever is a zoonotic disease caused by a mosquito-borne flavivirus, WNV. By its clinical sensitivity to the disease, the horse is a useful sentinel of infection. Because of the virus' low-level, short-term viraemia in horses, the primary tools used to diagnose WNV are serological tests. Inter-laboratory proficiency tests (ILPTs) were held in 2010 and 2013 to evaluate WNV serological diagnostic tools suited for the European network of National Reference Laboratories (NRLs) for equine diseases. These ILPTs were designed to evaluate the laboratories' and methods' performances in detectin...
Benjelloun A, El Harrak M, Calistri P, Loutfi C, Kabbaj H, Conte A, Ippoliti C, Danzetta ML, Belkadi B.West Nile virus-associated disease is one of the most widespread vector-borne diseases in the world. In Morocco, the first cases were reported in horses in 1996 and the disease re-emerged in 2003 and in 2010. The objective of this work was to study the epidemiological situation of WNV-associated infection in Morocco, by quantifying the seroprevalence of anti-WNV IgM and IgG antibodies in horses in different bioclimatic regions-zones of Morocco in 2011. During the months of May, June and July 2011, 840 serum samples were collected from horses in four regions characterized by different environme...
Pauvolid-Corrêa A, Komar N.Current methods for detecting Flavivirus antibodies are enzyme-linked immunosorbent assays (ELISAs) and neutralization tests, both of which require laboratories and trained staff. We evaluated the VectorTest™ West Nile Virus Antigen Assay in an inhibition platform (VecTest-inhibition assay [VIA]) as a simpler screening method for detecting antibodies for a variety of flaviviruses among a population of equines from Brazil. We found that the VIA is a field-deployable rapid method with 100% sensitivity and 64% specificity compared with blocking ELISA for the detection of group-specific Flavivir...
Cardinale E, Bernard C, Lecollinet S, Rakotoharinome VM, Ravaomanana J, Roger M, Olive MM, Meenowa D, Jaumally MR, Melanie J, Héraud JM, Zientara S....The circulation of West Nile virus (WNV) in horses was investigated in the Southwest Indian ocean. In 2010, blood samples were collected from a total of 303 horses originating from Madagascar, Mauritius, Reunion and the Seychelles and tested for WNV-specific antibodies. An overall seroprevalence of 27.39% was detected in the Indian Ocean with the highest WNV antibody prevalence of 46.22% (95% CI: [37.4-55.2%]) in Madagascar. The age and origin of the horses were found to be associated with the WNV infection risk. This paper presents the first seroprevalence study investigating WN fever in hors...
de Heus P, Kolodziejek J, Camp JV, Dimmel K, Bagó Z, Hubálek Z, van den Hoven R, Cavalleri JV, Nowotny N.We report details of the first seven equine cases of confirmed West Nile neuroinvasive disease in Austria. The cases presented during summer and autumn of 2016 (n = 2), 2017 (n = 3) and 2018 (n = 2). All horses showed gait abnormalities and 6 of 7 horses exhibited fasciculations and/or tremors, and we provide video recordings of these. Three horses also showed cranial nerve involvement. Following rapid improvement, three horses were discharged. Four horses were euthanized due to the severity of clinical signs and subjected to neuropathological examination. West Nile virus (WNV) lineage 2...
Ulbert S.West Nile virus (WNV) is a zoonotic virus that circulates in birds and is transmitted by mosquitoes. Incidentally, humans, horses and other mammals can also be infected. Disease symptoms caused by WNV range from fever to neurological complications, such as encephalitis or meningitis. Mortality is observed mostly in older and immunocompromised individuals. In recent years, epidemics caused by WNV in humans and horses have become more frequent in several Southern European countries, such as Italy and Greece. In 1999, WNV was introduced into the USA and spread over North America within a couple o...
Gardner IA, Wong SJ, Ferraro GL, Balasuriya UB, Hullinger PJ, Wilson WD, Shi PY, MacLachlan NJ.A prospective cohort study was used to estimate the incidence of West Nile virus (WNV) infection in a group of unvaccinated horses (n = 37) in California and compare the effects of natural WNV infection in these unvaccinated horses to a group of co-mingled vaccinated horses (n = 155). Horses initially were vaccinated with either inactivated whole virus (n = 87) or canarypox recombinant (n = 68) WNV vaccines during 2003 or 2004, prior to emergence of WNV in the region. Unvaccinated horses were serologically tested for antibodies to WNV by microsphere immunoassay incorporating recombinant WNV E ...
Laperriere V, Brugger K, Rubel F.The West Nile virus (WNV) is an arthropod-borne virus (arbovirus) circulating in a natural transmission cycle between mosquitoes (enzootic vectors) and birds (amplifying hosts). Additionally, mainly horses and humans (dead-end hosts) may be infected by blood-feeding mosquitoes (bridge vectors). We developed an epidemic model for the simulation of the WNV dynamics of birds, horses and humans in the U.S., which we apply to the Minneapolis metropolitan area (Minnesota). The SEIR-type model comprises a total of 19 compartments, that are 4 compartments for mosquitoes and 5 compartments or health st...
West Nile virus (WNV) is a member of the Japanese encephalitis serocomplex, which was first described in 1937 as neurotropic virus in Uganda in 1937. Subsequently, WNV was identified in the rest of the old-world and from 1999 in North America. Birds are the primary hosts, and WNV is maintained in a bird-mosquito-bird cycle, with pigs as amplifying hosts and humans and horses as incidental hosts. WNV transmission is warranted by mosquitoes, usually of the spp., with a tendency to spill over when mosquitoes' populations build up. Other types of transmissions have been described in endemic areas...
Arthropodborne viruses (arboviruses) are transmitted to humans primarily through the bites of infected mosquitoes and ticks. Symptomatic infections most often manifest as a systemic febrile illness and, less commonly, as neuroinvasive disease (e.g., meningitis, encephalitis, or acute flaccid paralysis). West Nile virus (WNV) is the leading cause of domestically acquired arboviral disease in the United States. However, several other arboviruses also cause seasonal outbreaks and sporadic cases. In 2011, CDC received reports of 871 cases of nationally notifiable arboviral diseases (excluding deng...
Bielefeldt-Ohmann H, Bosco-Lauth A, Hartwig AE, Uddin MJ, Barcelon J, Suen WW, Wang W, Hall RA, Bowen RA.Most natural West Nile virus (WNV) infections in humans and horses are subclinical or sub-lethal and non-encephalitic. Yet, the main focus of WNV research remains on the pathogenesis of encephalitic disease, mainly conducted in mouse models. We characterized host responses during subclinical WNV infection in horses and compared outcomes with those obtained in a novel rabbit model of subclinical WNV infection (Suen et al. 2015. Pathogens, 4: 529). Experimental infection of 10 horses with the newly emerging WNV-strain, WNVNSW2011, did not result in neurological disease in any animal but transcr...
Venter M, Human S, van Niekerk S, Williams J, van Eeden C, Freeman F.In 2010, lineage 1 West Nile virus was detected in South Africa in the brain of a pregnant mare that succumbed to neurologic disease and in her aborted fetus, suggesting an association with abortion in horses. All West Nile virus strains previously detected in horses and humans in South Africa were lineage 2.
Hadler J, Nelson R, McCarthy T, Andreadis T, Lis MJ, French R, Beckwith W, Mayo D, Archambault G, Cartter M.In 1999, Connecticut was one of three states in which West Nile (WN) virus actively circulated prior to its recognition. In 2000, prospective surveillance was established, including monitoring bird deaths, testing dead crows, trapping and testing mosquitoes, testing horses and hospitalized humans with neurologic illness, and conducting a human seroprevalence survey. WN virus was first detected in a dead crow found on July 5 in Fairfield County. Ultimately, 1,095 dead crows, 14 mosquito pools, 7 horses, and one mildly symptomatic person were documented with WN virus infection. None of 86 hospit...
Schuler LA, Khaitsa ML, Dyer NW, Stoltenow CL.To characterize an outbreak of West Nile virus (WNV) infection in horses in North Dakota in 2002, evaluate vaccine effectiveness, and determine horse characteristics and clinical signs associated with infection. Methods: Retrospective study. Methods: 569 horses. Methods: Data were obtained from veterinary laboratory records, and a questionnaire was mailed to veterinarians of affected horses. Results: Affected horses were defined as horses with typical clinical signs and seroconversion or positive results of virus isolation; affected horses were detected in 52 of the 53 counties and concentrate...
Leblond A, Sandoz A, Lefebvre G, Zeller H, Bicout DJ.Geographic information system and remote sensing technologies were used to identify landscape features associated with risk of West Nile virus transmission as defined by the presence of confirmed horse cases. SPOT-4 images of Camargue area were used to generate a map of landscape categories of epidemic foci and the geographic information system was employed to determine the proportion of landscape components surrounding 10 horse case sites and 17 control sites. The spatio-temporal analysis of the cases outbreak gave the best results for a spatial window of 9 km and a temporal window of 18 days...
Kitai Y, Shoda M, Kondo T, Konishi E.West Nile virus (WNV) is now widely distributed worldwide, except in most areas of Asia where Japanese encephalitis virus (JEV) is distributed. Considering the movement and migration of reservoir birds, there is concern that WNV may be introduced in Asian countries. Although manuals and guidelines for serological tests have been created in Japan in preparedness for the introduction of WNV, differential diagnosis between WNV and JEV may be complicated by antigenic cross-reactivities between these flaviviruses. Here, we generated a monoclonal antibody specific for the nonstructural protein 1 (NS...
Saiz JC.West Nile virus (WNV) is a widely distributed enveloped flavivirus transmitted by mosquitoes, which main hosts are birds. The virus sporadically infects equids and humans with serious economic and health consequences, as infected individuals can develop a severe neuroinvasive disease that can even lead to death. Nowadays, no WNV-specific therapy is available and vaccines are only licensed for use in horses but not for humans. While several methodologies for WNV vaccine development have been successfully applied and have contributed to significantly reducing its incidence in horses in the US, n...
Roth D, Henry B, Mak S, Fraser M, Taylor M, Li M, Cooper K, Furnell A, Wong Q, Morshed M.In 2009, an expansion of West Nile virus (WNV) into the Canadian province of British Columbia was detected. Two locally acquired cases of infection in humans and 3 cases of infection in horses were detected by ELISA and plaque-reduction neutralization tests. Ten positive mosquito pools were detected by reverse transcription PCR. Most WNV activity in British Columbia in 2009 occurred in the hot and dry southern Okanagan Valley. Virus establishment and amplification in this region was likely facilitated by above average nightly temperatures and a rapid accumulation of degree-days in late summer....
Mughini-Gras L, Mulatti P, Severini F, Boccolini D, Romi R, Bongiorno G, Khoury C, Bianchi R, Montarsi F, Patregnani T, Bonfanti L, Rezza G....In Italy, West Nile virus (WNV) equine outbreaks have occurred annually since 2008. Characterizing WNV vector habitat requirements allows for the identification of areas at risk of viral amplification and transmission. Maxent-based ecological niche models were developed using literature records of 13 potential WNV Italian vector mosquito species to predict their habitat suitability range and to investigate possible geographical associations with WNV equine outbreak occurrence in Italy from 2008 to 2010. The contribution of different environmental variables to the niche models was also assessed...
Guerrero-Carvajal F, Bravo-Barriga D, Martín-Cuervo M, Aguilera-Sepúlveda P, Ferraguti M, Jiménez-Clavero MÁ, Llorente F, Alonso JM, Frontera E.West Nile virus (WNV) is a mosquito-borne emerging virus in Europe with capacity to cause neurological complications such as encephalitis or meningoencephalitis in humans, birds or equids. In Spain, WNV is actively circulating in mosquitoes, birds and horses in different regions, but never has been deeply studied in Extremadura. Therefore, the aim of this study was to evaluate the seroprevalence of WNV in equids of those areas and to analyse the risk factors associated with exposure to the virus. A total of 199 out of 725 equids presented antibodies against WNV by competition ELISA (27.45%), w...
Quirin R, Salas M, Zientara S, Zeller H, Labie J, Murri S, Lefrançois T, Petitclerc M, Martinez D.To determine whether West Nile virus (WNV) had reached the archipelago of Guadeloupe, a serologic study in horses and birds was conducted in 2002. Immunoglobulin (Ig) G, IgM, enzyme-linked immunosorbent assay, and seroneutralization tests identified WNV infection in horses and chickens. Six months later, a high rate of seroconversion was observed in horses.
Hirota J, Nishi H, Matsuda H, Tsunemitsu H, Shimiz S.Flavivirus-infected sera are known to show cross-reactions in serodiagnoses of heterologous flavivirus infections. Japanese encephalitis virus (JEV) is endemic in Asia and, in Japan, many horses are vaccinated against JEV. However, the cross-reactivity level of JEV-vaccinated horse sera in the serodiagnosis of West Nile virus (WNV) has not been clarified. The antibody cross-reactivity of JEV-vaccinated horse sera in WNV serological tests, such as the plaque reduction neutralization test (PRNT), IgG indirect ELISA (IgG-ELISA) and hemagglutination inhibition (HI) test, was examined. All JEV-vacc...
Bergmann F, Trachsel DS, Stoeckle SD, Bernis Sierra J, Lübke S, Groschup MH, Gehlen H, Ziegler U.Following the introduction of the West Nile virus (WNV) into eastern Germany in 2018, increasing infections have been diagnosed in birds, equines, and humans over time, while the spread of WNV into western Germany remained unclear. We screened 437 equine sera from 2018 to 2020, excluding vaccinated horses, collected from convenience sampled patients in the eastern and western parts of Germany, for WNV-specific antibodies (ELISAs followed by virus/specific neutralization tests) and genomes (RT-qPCRs). Clinical presentations, final diagnoses, and demographic data were also recorded. In the easte...
Bertram FM, Thompson PN, Venter M.Although West Nile virus (WNV) is endemic to South Africa (RSA), it has only become recognized as a significant cause of neurological disease in humans and horses locally in the past 2 decades, as it emerged globally. This article describes the epidemiological and clinical presentation of WNV in horses across RSA during 2016-2017. In total, 54 WNV-positive cases were identified by passive surveillance in horses with febrile and/or neurological signs at the Centre for Viral Zoonoses, University of Pretoria. They were followed up and compared to 120 randomly selected WNV-negative controls with t...
Aharonson-Raz K, Lichter-Peled A, Tal S, Gelman B, Cohen D, Klement E, Steinman A.With the rapid global spread of West Nile virus (WNV) and the endemic state it has acquired in new geographical areas, we hereby bring a thorough serological investigation of WNV in horses in a longstanding endemic region, such as Israel. This study evaluates the environmental and demographic risk factors for WNV infection in horses and suggests possible factors associated with the transition from endemic to epidemic state. West Nile virus seroprevalence in horses in Israel was determined throughout a period of more than a decade, before (1997) and after (2002 and 2013) the massive West Nile f...
Ziegler U, Angenvoort J, Klaus C, Nagel-Kohl U, Sauerwald C, Thalheim S, Horner S, Braun B, Kenklies S, Tyczka J, Keller M, Groschup MH.West Nile virus (WNV) is a mosquito-borne viral pathogen of global importance and is considered to be the most widespread flavivirus in the World. Horses, as dead-end hosts, can be infected by bridge mosquito vectors and undergo either subclinical infections or develop severe neurological diseases. The aim of this study was to detect WNV specific antibodies in horses in Germany as an indicator for an endemic circulation of WNV. Sera from more than 5,000 horses (primarily fallen stock animals) were collected in eight different federal states of Germany from 2010 to 2012. Sera were screened by a...
Vanhomwegen J, Beck C, Desprès P, Figuerola A, García R, Lecollinet S, López-Roig M, Manuguerra JC, Serra-Cobo J.The presence of major arbovirus vector species, climate change that promotes the expansion and increase of their populations, and potential animal reservoirs mean that vector-borne diseases represent a significant health risk for Mallorca's inhabitants. Microbiological monitoring of circulating arboviruses, particularly flaviviruses causing encephalitis, was initiated using domestic horses from localities near wetlands as "sentinel" hosts. A total of 291 blood samples were taken from 172 horses between 2011 and 2012, using paired samples to highlight seroconversion events. A multiplex immunoas...
Calzolari M, Monaco F, Montarsi F, Bonilauri P, Ravagnan S, Bellini R, Cattoli G, Cordioli P, Cazzin S, Pinoni C, Marini V, Natalini S, Goffredo M....West Nile virus (WNV) is one of the most serious public health threats that Europe and the Mediterranean countries are currently facing. In Italy, WNV emerged in 1998 and has been circulating since 2008. To tackle its continuous incursions, Italian national and regional institutions set up a surveillance program, which includes the serological screening of sentinel horses, sentinel-chickens and backyard poultry flocks and the surveillance on all equine neurological cases, resident captured and wild dead birds, and vectors. This communication aims to assess the importance of the entomological s...
García-Bocanegra I, Belkhiria J, Napp S, Cano-Terriza D, Jiménez-Ruiz S, Martínez-López B.During the last decade, West Nile virus (WNV) outbreaks have increased sharply in both horses and human in Europe. The aims of this study were to evaluate characteristics and spatio-temporal distribution of WNV outbreaks in horses in Spain between 2010 and 2016 in order to identify the environmental variables most associated with WNV occurrence and to generate high-resolution WNV suitability maps to inform risk-based surveillance strategies in this country. Between August 2010 and November 2016, a total of 403 WNV suspected cases were investigated, of which, 177 (43.9%) were laboratory confirm...
van den Hurk AF, Hall-Mendelin S, Webb CE, Tan CS, Frentiu FD, Prow NA, Hall RA.In 2011, a variant of West Nile virus Kunjin strain (WNVKUN) caused an unprecedented epidemic of neurological disease in horses in southeast Australia, resulting in almost 1,000 cases and a 9% fatality rate. We investigated whether increased fitness of the virus in the primary vector, Culex annulirostris, and another potential vector, Culex australicus, contributed to the widespread nature of the outbreak. Methods: Mosquitoes were exposed to infectious blood meals containing either the virus strain responsible for the outbreak, designated WNVKUN2011, or WNVKUN2009, a strain of low virulence th...
Thompson NN, Auguste AJ, Coombs D, Blitvich BJ, Carrington CV, da Rosa AP, Wang E, Chadee DD, Drebot MA, Tesh RB, Weaver SC, Adesiyun AA.Seroprevalence rates of selected arboviruses in animal populations in Trinidad were determined using serum samples collected between 2006 and 2009 from horses (n=506), cattle (n=163), sheep (n=198), goats (n=82), pigs (n=184), birds (n=140), rodents (n=116), and other vertebrates (n=23). The sera were screened for antibodies to West Nile virus (WNV), St. Louis encephalitis virus (SLEV), Ilheus virus (ILHV), Bussuquara virus (BSQV), Venezuelan equine encephalitis virus (VEEV), eastern equine encephalitis virus (EEEV), and western equine encephalitis virus (WEEV), using hemagglutination inhibiti...
Gingrich JB, Williams GM.Paucity of data on host-feeding patterns and behavior of 43 mosquito species that are reported as suspected West Nile virus (WN) vectors has limited full evaluation of their vectorial capacity. Recent studies addressing this issue need additional confirmation and should also be expanded to include collections of species or subpopulations attracted to humans. We used 4 types of collection methods to collect mosquitoes, including omnidirectional Fay-Prince traps, Centers for Disease Control-type light traps, gravid traps, and human-landing collections. Mosquitoes were collected during 2 full WN ...
Hall RA, Khromykh AA.West Nile virus (WNV) is a mosquito-borne flavivirus that is emerging as a global pathogen. In the last decade, virulent strains of the virus have been associated with significant outbreaks of human and animal disease in Europe, the Middle East and North America. Efforts to develop human and veterinary vaccines have taken both traditional and novel approaches. A formalin-inactivated whole virus vaccine has been approved for use in horses. DNA vaccines coding for the structural WNV proteins have also been assessed for veterinary use and have been found to be protective in mice, horses and birds...
