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.
Bowen RA, Bosco-Lauth A, Syvrud K, Thomas A, Meinert TR, Ludlow DR, Cook C, Salt J, Ons E.Over the last years West Nile virus (WNV) lineage 2 has spread from the African to the European continent. This study was conducted to demonstrate efficacy of an inactivated, lineage 1-based, WNV vaccine (Equip WNV) against intrathecal challenge of horses with a recent isolate of lineage 2 WNV. Twenty horses, sero-negative for WNV, were enrolled and were randomly allocated to one of two treatment groups: an unvaccinated control group (T01, n=10) and a group administered with Equip WNV (T02, n=10). Horses were vaccinated at Day 0 and 21 and were challenged at day 42 with WNV lineage 2, Nea Sant...
Di Gennaro A, Lorusso A, Casaccia C, Conte A, Monaco F, Savini G.A serum neutralization assay (SN) was compared with the official plaque reduction neutralization test for the quantitation of West Nile virus antibodies. A total of 1,348 samples from equid sera and 38 from human sera were tested by these two methods. Statistically significant differences were not observed, thus supporting the use of SN for routine purposes.
Pradier S, Sandoz A, Paul MC, Lefebvre G, Tran A, Maingault J, Lecollinet S, Leblond A.To assess environmental and horse-level risk factors associated with West Nile Virus (WNV) circulation in Camargue, Southern France, a serosurvey was conducted on non-vaccinated horses (n = 1159 from 134 stables) in 2007 and 2008. Fifteen Landsat images were examined to quantify areas with open water and flooded vegetation around sampled horses. Mean percentages of areas of open water and flooded vegetation, as well as variations in these percentages between 3 periods (November to February = NOT, March to July = END and August to October = EPI), were calculated for buffers of 2 km radius aroun...
Ben Hassine T, De Massis F, Calistri P, Savini G, BelHaj Mohamed B, Ranen A, Di Gennaro A, Sghaier S, Hammami S.In the last fifteen years, West Nile Virus (WNV) has dramatically expanded its geographic range and is now considered the most widespread arbovirus in the world. In Tunisia, West Nile Fever (WNF) outbreaks were reported in humans in 1997, 2003 and 2012. Usutu Virus (USUV), which is a 'new' emerging Flavivirus antigenically close to WNV, has never been reported in Tunisia. A serological investigation in 284 equids was conducted in 2012 in the southern west region of the country to assess the presence and prevalence of the WNV and USUV infection. Of the 284 samples tested by competitive enzyme-l...
Ergunay K, Gunay F, Erisoz Kasap O, Oter K, Gargari S, Karaoglu T, Tezcan S, Cabalar M, Yildirim Y, Emekdas G, Alten B, Ozkul A.West Nile virus (WNV), a mosquito-borne flavivirus with significant impact on human and animal health, has recently demonstrated an expanded zone of activity globally. The aim of this study is to investigate the frequency and distribution of WNV infections in potential vectors and several mammal and avian species in Turkey, where previous data indicate viral circulation. The study was conducted in 15 provinces across Turkey during 2011-2013. In addition, the entomological study was extended to 4 districts of the Turkish Republic of Northern Cyprus. WNV exposure was determined in humans, horses...
Suen WW, Prow NA, Hall RA, Bielefeldt-Ohmann H.West Nile virus (WNV) is an important emerging neurotropic virus, responsible for increasingly severe encephalitis outbreaks in humans and horses worldwide. However, the mechanism by which the virus gains entry to the brain (neuroinvasion) remains poorly understood. Hypotheses of hematogenous and transneural entry have been proposed for WNV neuroinvasion, which revolve mainly around the concepts of blood-brain barrier (BBB) disruption and retrograde axonal transport, respectively. However, an over‑representation of in vitro studies without adequate in vivo validation continues to obscure our...
Medić S, van den Hoven R, Petrović T, Lupulović D, Nowotny N.This study was conducted to evaluate the seroprevalence of West Nile virus (WNV) in the horse population of northern Serbia. Furthermore, it aimed to provide insight and an updated overview on the circulation of this re-emerging pathogen in this part of southeastern Europe. At the time of manuscript preparation, no clinical cases of WNV infection in horses were reported in this area. Methods: Between 2007 and 2011, a total of 252 equine serum samples were collected from seven different locations in northern Serbia. The presence of WNV-reactive IgG antibodies was examined by using commercial an...
Saegerman C, Alba-Casals A, García-Bocanegra I, Dal Pozzo F, van Galen G.West Nile fever (WNF) is a viral zoonotic infection caused by a mosquito-borne flavivirus of the Flaviviridae family. According to a comparative study, the passive surveillance of horses by equine veterinarians appeared to be the most cost-effective system in the European context of WNF. Clinical data issued from a passive epidemiosurveillance network from September 2010 to December 2011 on horses in Spain were statistically compared and used to develop a predictive diagnostic decision tree, both with the aim to improve the early clinical detection of WNF in horses. Although clinical signs wer...
Mangana-Vougiouka O, Boutsini S, Ntousi D, Patakakis M, Orfanou E, Zafiropoulou K, Dilaveris D, Panagiotatos D, Nomikou K.During the period 2001 to 2008, a total of 7,872 equine sera were tested at the Centre of Veterinary Institutes of Athens. Antibodies against seven infectious diseases of equids were determined: equine infectious anaemia (EIA), African horse sickness (AHS), equine viral arteritis (EVA), West Nile encephalitis (WNE), glanders, piroplasmosis and dourine. Tests for the four viral diseases found 4.5% seropositivity for EIA, 0% for AHS, 3.3% for EVA and 4% for WNE. All sera tested for glanders antibodies were negative. Tests for piroplasmosis detected antibodies against T. equi and B. caballi in 12...
Ludu Oslobanu EL, Mihu-Pintilie A, Anită D, Anita A, Lecollinet S, Savuta G.The presence of West Nile virus (WNV) in humans has been known in Romania since the 1950s; the 1996 epidemics emphasized the reemergence potential of WNV in Romania. Serological surveys made on susceptible species, known as good sentinels or reservoir hosts, e.g., horses, wild and domestic birds were undertaken from 2006-2011. Our results corroborated incidence data in human patients and other recent seroprevalence studies in animals, and should partially clarify the emergence of WNV in the eastern rural territories of Romania. It also highlighted risk zones for endemic WNV infection in Romani...
Bingham J, Payne J, Harper J, Frazer L, Eastwood S, Wilson S, Lowther S, Lunt R, Warner S, Carr M, Hall RA, Durr PA.West Nile virus (WNV; family Flaviviridae; genus Flavivirus) group members are an important cause of viral meningoencephalitis in some areas of the world. They exhibit marked variation in pathogenicity, with some viral lineages (such as those from North America) causing high prevalence of severe neurological disease, whilst others (such as Australian Kunjin virus) rarely cause disease. The aim of this study was to characterize WNV disease in a mouse model and to elucidate the pathogenetic features that distinguish disease variation. Tenfold dilutions of five WNV strains (New York 1999, MRM16 a...
Berxholi K, Ziegler U, Rexhepi A, Schmidt K, Mertens M, Korro K, Cuko A, Angenvoort J, Groschup MH.Serum samples collected from 167 equines of 12 districts in Albania were tested for West Nile virus-specific antibodies by enzyme-linked immunosorbent assay and virus neutralization assay, using WNV lineage 1 and 2. In addition, 95 bird serum samples from Albania and 29 horse samples from Kosovo were tested in ELISA. An overall seroprevalence rate of 22% was found in horses from Albania, whereas no specific antibodies were found in the equine samples from Kosovo and the bird samples. This is the first report indicating WNV infections in animals in Albania, and the first reported seroprevalence...
Pauvolid-Corrêa A, Campos Z, Juliano R, Velez J, Nogueira RM, Komar N.A recent study reported neutralizing antibodies to West Nile virus (WNV) in horses from four ranches of southern Pantanal. To extend that study, a serosurvey for WNV and 11 Brazilian flaviviruses was conducted with 760 equines, 238 sheep and 61 caimans from 17 local cattle ranches. Among the tested equines, 32 were collected from a ranch where a neurologic disorder outbreak had been recently reported. The sera were initially screened by using a blocking ELISA and then titrated by 90% plaque-reduction neutralization test (PRNT90) for 12 flaviviruses. Employing the criterion of 4-fold greater ti...
Abutarbush SM, Al-Majali AM.The objectives of this study are to report clinical WNV infection in horses and to determine the seroprevalence of and risk factors for WNV infection in horses in Jordan. In late summer and early fall of 2012, two mares were presented for evaluation of neurological signs. The first mare had hind-limb ataxia. The second mare was slightly depressed and lethargic. She had ataxia in her four limbs and cranial nerves deficits. Both horses were found positive for WNV IgM antibodies using commercial IgM-capture ELISA test. Both horses were treated symptomatically and recovered uneventfully. The occur...
Burgueño A, Spinsanti L, Díaz LA, Rivarola ME, Arbiza J, Contigiani M, Delfraro A.St. Louis encephalitis virus (SLEV) and West Nile virus (WNV) belong to the Japanese encephalitis antigenic complex (Flavivirus genus, Flaviviridae family). They show antigenic close relationships and share many similarities in their ecology. Both are responsible for serious human diseases. The aim of this study was to investigate the presence of neutralizing antibodies to these viruses in horses from Uruguay. To do this, 425 horse sera were collected in 2007 and analyzed by plaque reduction neutralization tests. As a result, 205 sera (48.2%) were found positive for SLEV, with titers ranging b...
Vignjević G, Vrućina I, Sestak I, Turić N, Bogojević MS, Merdić E.The West Nile Virus (WNV) is a zoonotic arbovirus that has recently been causing outbreaks in many countries in southern and Central Europe. In 2012, for the first time, it caused an outbreak in eastern Croatia with total of 7 human clinical cases. With an aim of assisting public health personnel in order to improve survey protocols and vector control, the high risk areas of the WNV transmission were estimated and mapped. The study area included cities of Osijek and Slavonski Brod and 8 municipalities in Vukovarsko-Srijemska County. Risk estimation was based on seroprevalence of WNV infections...
Prow NA.West Nile virus (WNV) is a mosquito-borne virus responsible for outbreaks of viral encephalitis in humans and horses, with particularly virulent strains causing recent outbreaks of disease in Eastern Europe, the Middle East and North America. A strain of WNV, Kunjin (WNVKUN), is endemic in northern Australia and infection with this virus is generally asymptomatic. However in early 2011, an unprecedented outbreak of encephalitis in horses occurred in south-eastern Australia, resulting in mortality in approximately 10%-15% of infected horses. A WNV-like virus (WNVNSW2011) was isolated and found ...
Donadieu E, Bahuon C, Lowenski S, Zientara S, Coulpier M, Lecollinet S.West Nile virus (WNV) is a neurotropic flavivirus that cycles between mosquitoes and birds but that can also infect humans, horses, and other vertebrate animals. In most humans, WNV infection remains subclinical. However, 20%-40% of those infected may develop WNV disease, with symptoms ranging from fever to meningoencephalitis. A large variety of WNV strains have been described worldwide. Based on their genetic differences, they have been classified into eight lineages; the pathogenic strains belong to lineages 1 and 2. Ten years ago, Beasley et al. (2002) found that dramatic differences exist...
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...
Mazzei M, Savini G, Di Gennaro A, Macchioni F, Prati MC, Guzmàn LR, Tolari F.West Nile virus (WNV) is a mosquito-borne virus belonging to the family Flaviviridae included in the Japanese encephalitis antigenic complex (JEAC). A seroepidemiological study was carried out in 2011 using 160 horse sera collected from different areas of Bolivia to investigate the presence of WNV antibody. A high proportion (59.4%) of the tested sera were positive to a commercially available WNV competitive enzyme-linked immunosorbent assay (C-ELISA). Sixty-six randomly selected C-ELISA-positive sera were further tested by WNV plaque reduction neutralization test (PRNT), virus neutralization ...
Ziegler U, Skrypnyk A, Keller M, Staubach C, Bezymennyi M, Damiani AM, Osterrieder N, Groschup MH.West Nile virus (WNV) is a mosquito-borne virus of global importance. Over the last two decades, it has been responsible for significant numbers of cases of illness in humans and animals in many parts of the world. In Ukraine, WNV infections in humans and birds were first reported more than 25 years ago, yet the current epidemiological status is quite unclear. In this study, serum samples from over 300 equines were collected and screened in order to detect current WNV activity in Ukraine with the goal to estimate the risk of infection for humans and horses. Sera were tested by enzyme-linked im...
Silva JR, Medeiros LC, Reis VP, Chavez JH, Munhoz TD, Borges GP, Soares OA, Campos CH, Machado RZ, Baldani CD, Silva ML, Faria JL, Silva EE....Since the emergence of West Nile virus (WNV) in North America in 1999, there have been several reports of WNV activity in Central and South American countries. To detect WNV in Brazil, we performed a serological survey of horses from different regions of Brazil using recombinant peptides from domain III of WNV. Positive samples were validated with the neutralisation test. Our results showed that of 79 ELISA-positive horses, nine expressed WNV-specific neutralising antibodies. Eight of the infected horses were from the state of Mato Grosso do Sul and one was from the state of Paraíba. Our resu...
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...
Ometto T, Durigon EL, de Araujo J, Aprelon R, de Aguiar DM, Cavalcante GT, Melo RM, Levi JE, de Azevedo Júnior SM, Petry MV, Neto IS, Serafini P....West Nile virus (WNV) is an emergent pathogen that is widely distributed in North and Central America. The recent introduction in South America has focused attention on the spread of WNV across Southern American countries. The transmission network involves mosquitoes, birds, horses and humans. Methods: The serological evaluation of sera from 678 equids and 478 birds was performed using a WNV-specific blocking ELISA, and only the positive results were confirmed by plaque reduction neutralisation tests (PRNTs). Molecular analysis was performed on sera from 992 healthy equids and on 63 macerates ...
Angenvoort J, Brault AC, Bowen RA, Groschup MH.West Nile virus (WNV) is a flavivirus transmitted between certain species of birds and mosquito vectors. Tangential infections of equids and subsequent equine epizootics have occurred historically. Although the attack rate has been estimated to be below 10%, mortality rates can approach 50% in horses that present clinical disease. Symptoms are most commonly presenting in the form of encephalitis with ataxia as well as limb weakness, recumbency and muscle fasciculation. The most effective strategy for prevention of equine disease is proper vaccination with one of the numerous commercially avail...
Hubálek Z, Ludvíková E, Jahn P, Treml F, Rudolf I, Svobodová P, Šikutová S, Betášová L, Bíreš J, Mojžíš M, Tinák M, Boldižár M....A serological survey for West Nile virus (WNV) infection involved 395 horses from 43 administrative districts of the Czech Republic (163 animals) and 29 districts of Slovakia (232 animals), sampled between 2008 and 2011. Using a plaque-reduction neutralization microtest, antibodies to WNV were not detected in any horse from the Czech Republic, whereas 19 nonvaccinated horses from Slovakia had specific antibodies to WNV (no cross-reactions were observed with tick-borne encephalitis and Usutu flaviviruses in those animals). The seropositivity rate of nonvaccinated horses in Slovakia was 8.3% (95...
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...
Martín-Acebes MA, Blázquez AB, de Oya NJ, Escribano-Romero E, Shi PY, Saiz JC.West Nile virus (WNV) is a worldwide distributed mosquito-borne flavivirus that naturally cycles between birds and mosquitoes, although it can infect multiple vertebrate hosts including horses and humans. This virus is responsible for recurrent epidemics of febrile illness and encephalitis, and has recently become a global concern. WNV requires to transit through intracellular acidic compartments at two different steps to complete its infectious cycle. These include fusion between the viral envelope and the membrane of endosomes during viral entry, and virus maturation in the trans-Golgi netwo...
Barbic L, Vilibic-Cavlek T, Listes E, Stevanovic V, Gjenero-Margan I, Ljubin-Sternak S, Pem-Novosel I, Listes I, Mlinaric-Galinovic G, Di Gennaro A....We report the first serological evidence of Usutu virus (USUV) infection in horses in Croatia. During 2011, 1380 horse serum samples from healthy animals were collected from six northern Croatian counties. All samples were first screened for West Nile virus (WNV) immunoglobulin G (IgG) antibodies using an enzyme-linked immunosorbent assay (ELISA). Sixty-nine WNV ELISA-reactive samples were further tested for WNV antibodies by a virus neutralization assay (VN assay) and plaque reduction neutralization test (PRNT), and USUV by a VN assay and tick-borne encephalitis virus (TBEV) antibodies by PRN...
Chinikar S, Shah-Hosseini N, Mostafavi E, Moradi M, Khakifirouz S, Jalali T, Goya MM, Shirzadi MR, Zainali M, Fooks AR.This study was undertaken to determine the seroprevalence of West Nile virus (WNV) in human and equine sera in Iran. Blood samples were tested from 300 human samples and 315 equine samples in five geographic zones of north and central parts of Iran between 2010 and 2012. All samples were tested for the immunoglobulin G (IgG) antibody to WNV by using an enzyme-linked immunosorbent assay (ELISA). Of all samples, 4 (1.3%) human and 9 (2.8%) equines were considered to be seropositive for WNV. These results suggest circulation and exposure of the human and equine populations to WNV in Iran.
Jiménez-Clavero MÁ.Environmental changes have an undoubted influence on the appearance, distribution, and evolution of infectious diseases, and notably on those transmitted by vectors. Global change refers to environmental changes arising from human activities affecting the fundamental mechanisms operating in the biosphere. This paper discusses the changes observed in recent times with regard to some important arboviral (arthropod-borne viral) diseases of animals, and the role global change could have played in these variations. Two of the most important arboviral diseases of animals, bluetongue (BT) and West Ni...
Lian M, Warner RD, Alexander JL, Dixon KR.In 2002, West Nile virus (WNV) first appeared in Texas. Surveillance data were retrospectively examined to explore the temporal and spatial characteristics of the Texas equine WNV epidemic in 2002. Using Geographic Information Systems (GIS) and the Spatial and Space-Time Scan (SaTScan) statistics, we analyzed 1421 of the reported equine WNV cases from six contiguous state Health Service Regions (HSRs), comprising 158 counties, in western, northern, central and eastern Texas. Results: Two primary epidemic peaks occurred in Epidemiological (Epi) week 35 (August 25 to 31) and Epi week 42 (October...
Barros SC, Ramos F, Fagulha T, Duarte M, Henriques M, Luís T, Fevereiro M.The circulation of West Nile virus in Portugal was assessed by serological surveys conducted during 2004-2010 in horses and birds. The detection of WNV antibodies in both species in all the years covered by the study as well as the presence of anti-WNV IgM in symptomatic horses that had not traveled outside the country, support the notion that WNV circulates in Portugal.
Gershwin LJ, Netherwood KA, Norris MS, Behrens NE, Shao MX.Vaccination of horses is performed annually or semi-annually with multiple viral antigens, either in a combination vaccine or as separate injections. While this practice undoubtedly prevents infection from such diseases as rabies, equine influenza, West Nile virus, and equine herpes virus, the procedure is not without repercussions. Hypersensitivity reactions, including fatal anaphylactic shock, after vaccination, although uncommon, have increased in incidence in recent years. Studies reported herein document the development of IgE antibodies against non-target antigen components of equine vir...
Castillo-Olivares J, Mansfield KL, Phipps LP, Johnson N, Tearle J, Fooks AR.West Nile virus (WNV) has re-emerged as an important pathogen for humans and horses, which are considered to be incidental 'dead-end' hosts. We have demonstrated that horses are susceptible to experimental infection with WNV and that horses infected with either WNV lineage 1 or lineage 2 elicit a similar antibody profile in serum samples. These data suggest that virus-neutralizing antibody responses persist for longer than WNV-specific IgM levels in serum and that there are not any notable differences in the antibody profile following experimental infection of horses with either WNV lineage 1 ...
Hobson-Peters J, Toye P, Sánchez MD, Bossart KN, Wang LF, Clark DC, Cheah WY, Hall RA.Using a monoclonal antibody directed to domain I of the West Nile virus (WNV) envelope (E) protein, we identified a continuous (linear) epitope that was immunogenic during WNV infection of horses. Using synthetic peptides, this epitope was mapped to a 19 aa sequence (WN19: E147-165) encompassing the WNV NY99 E protein glycosylation site at position 154. The inability of WNV-positive horse and mouse sera to bind the synthetic peptides indicated that glycosylation was required for recognition of peptide WN19 by WNV-specific antibodies in sera. N-linked glycosylation of WN19 was achieved through ...
Lefrançois T, Blitvich BJ, Pradel J, Molia S, Vachiéry N, Pallavicini G, Marlenee NL, Zientara S, Petitclerc M, Martinez D.We conducted extensive surveillance for West Nile virus infection in equines and chickens in Guadeloupe in 2003-2004. We showed a high seroprevalence in equines in 2003 related to biome, followed by a major decrease in virus circulation in 2004. No human or equine cases were reported during the study.
Joó K, Bakonyi T, Szenci O, Sárdi S, Ferenczi E, Barna M, Malik P, Hubalek Z, Fehér O, Kutasi O.West Nile virus (WNV) mainly infects birds, horses and humans. Outcomes of the infection range from mild uncharacteristic signs to fatal neurologic disease. The main objectives of the present study were to measure serum IgG and IgM antibodies in naturally exposed and vaccinated horses and to compare results of haemagglutination inhibition test (HIT), enzyme-linked immunosorbent assay (ELISA) and plaque reduction neutralisation test (PRNT). Altogether 224 animals were tested by HIT for WNV antibodies and 41 horses were simultaneously examined by ELISA and PRNT. After primary screening for WNV a...
Humblet MF, Vandeputte S, Fecher-Bourgeois F, Léonard P, Gosset C, Balenghien T, Durand B, Saegerman C.This study aimed at estimating, in a prospective scenario, the potential economic impact of a possible epidemic of WNV infection in Belgium, based on 2012 values for the equine and human health sectors, in order to increase preparedness and help decision-makers. Modelling of risk areas, based on the habitat suitable for Culex pipiens, the main vector of the virus, allowed us to determine equine and human populations at risk. Characteristics of the different clinical forms of the disease based on past epidemics in Europe allowed morbidity among horses and humans to be estimated. The main costs ...
Mann RA, Fegan M, O'Riley K, Motha J, Warner S.Virus was detected in the central nervous system (CNS) tissue of 11 horses from Victoria that died displaying neurological symptoms during an outbreak of disease in Australia in 2011. Five horses were identified as being infected with Murray Valley encephalitis virus (MVEV) and 6 as being infected with West Nile virus subtype Kunjin (WNV(KUN)). Analysis of partial sequence information from the NS5 and E genes indicated that the MVEVs within the samples were highly homogenous and all belonged to lineage I, which is enzootic to the tropical regions of northern Australia. Likewise, analysis of pa...
Yeh JY, Lee JH, Seo HJ, Park JY, Moon JS, Cho IS, Lee JB, Park SY, Song CS, Choi IS.The aim of this study was to develop a highly sensitive and specific one-step duplex reverse transcriptase PCR (RT-PCR) assay for the simultaneous and differential detection of West Nile (WNV) and Japanese encephalitis (JEV) viruses. The bioinformatic analysis of published sequences of WNV and JEV revealed conserved regions not targeted by previously reported primers. A total of 13 primers were designed based on these regions to detect all of the WNV and JEV lineages and to discriminate between the two viruses by the generation of 482- and 241-bp cDNA products, respectively. The results indica...
Burkett-Cadena ND, Gibson J, Lauth M, Stenn T, Acevedo C, Xue RD, McNelly J, Northey E, Hassan HK, Fulcher A, Bingham AM, van Olphen J, van Olphen A....Zoonotic mosquito-borne viruses, such as the West Nile virus (WNV) and eastern equine encephalitis virus (EEEV), are major public health threats in the United States. Early detection of virus transmission and targeted vector management are critical to protect humans against these pathogens. Sentinel chickens and pool screening of mosquitoes, the most widely used methods of arbovirus early detection, have technical time-lags that compromise their early-detection value. The exploitation of sugar-feeding by trapped mosquitoes for arbovirus surveillance may represent a viable alternative to other ...
Ndiva Mongoh M, Hearne R, Dyer NW, Khaitsa ML.This study estimated economic impacts associated with the West Nile virus (WNV) outbreak in horses for North Dakota in 2002. The 2002 epidemic in the United States was the largest meningoencephalitis epidemic reported in the Western Hemisphere. Over 15,257 horse cases were reported in 43 states with most cases occurring in central United States. North Dakota reported over 569 horse cases, with a mortality rate of 22%. The total costs incurred by the state were approximately US$1.9 million. The costs incurred by horse owners were about US$1.5 million. Of the US$1.5 million, about US$781,203 and...
Martín-Acebes MA, Blázquez AB, de Oya NJ, Escribano-Romero E, Shi PY, Saiz JC.West Nile virus (WNV) is a worldwide distributed mosquito-borne flavivirus that naturally cycles between birds and mosquitoes, although it can infect multiple vertebrate hosts including horses and humans. This virus is responsible for recurrent epidemics of febrile illness and encephalitis, and has recently become a global concern. WNV requires to transit through intracellular acidic compartments at two different steps to complete its infectious cycle. These include fusion between the viral envelope and the membrane of endosomes during viral entry, and virus maturation in the trans-Golgi netwo...
Hobson-Peters J, Arévalo C, Cheah WY, Blitvich BJ, Tan CS, Sandis A, Araya LN, Hernández JL, Toye P, Hall RA.We conducted a serosurvey for West Nile virus (WNV) infection in equines in Costa Rica in 2004. Antibodies to WNV were detected in 28% of the horses using an epitope blocking ELISA that is specific for WNV. WNV infection was confirmed for a subset of these sera by plaque reduction neutralization tests and Western blot. This is the first evidence of WNV activity in Costa Rica.
de Heus P, Kolodziejek J, Hubálek Z, Dimmel K, Racher V, Nowotny N, Cavalleri JV.The emergence of West Nile virus (WNV) and Usutu virus (USUV) in addition to the autochthonous tick-borne encephalitis virus (TBEV) in Europe causes rising concern for public and animal health. The first equine case of West Nile neuroinvasive disease in Austria was diagnosed in 2016. As a consequence, a cross-sectional seroprevalence study was conducted in 2017, including 348 equids from eastern Austria. Serum samples reactive by ELISA for either flavivirus immunoglobulin G or M were further analyzed with the plaque reduction neutralization test (PRNT-80) to identify the specific etiologic age...
Ward MP, Levy M, Thacker HL, Ash M, Norman SK, Moore GE, Webb PW.To describe an outbreak of encephalomyelitis caused by West Nile virus (WNV) in horses in northern Indiana. Methods: Case series. Methods: 170 horses. Methods: Horses with clinical signs suggestive of encephalomyelitis caused by WNV were examined. Date, age, sex, breed, and survival status were recorded. Serum samples were tested for anti-WNV antibodies, and virus isolation was attempted from samples of brain tissue. Climate data from local weather recording stations were collected. An epidemic curve was constructed, and case fatality rate was calculated. Results: The most common clinical sign...
Mall MP, Kumar A, Malik SV.A study on seroprevalence of Japanese Encephalitis (JE), West Nile (WN) and Dengue-2 (DN-2) was undertaken in and around Bareilly, Uttar Pradesh to explore the role of non-human hosts in the natural cycle of these infections. A total of 1449 animal sera samples collected from 104 dogs, 170 pigs, 170 horses, 333 buffaloes, 252 cattle, 168 sheep and 252 goats were screened for antibodies against JE, WN and DN-2 by Micro-haemagglutination inhibition (HI) test employing 4 to 16 HA units of JE, WN and DN-2 antigens. The HI positivity against JE was found in dogs (55.77%) followed by pigs (40%), hor...
Monath TP.The arthropod-borne encephalitides are an important cause of equine and human morbidity in the Americas. Between 1975 and 1978, 6970 human cases of arboviral encephalitis were reported in the United States of America; however, this represents only a fraction of the true incidence. St Louis encephalitis (4824 cases), California encephalitis (1035 cases), and western equine encephalitis (WEE, 947 cases) accounted for 98.5% of all reported infections. Approximately 1000-4000 cases of equine encephalitis occur annually in the United States, the majority due to WEE. In tropical America, important o...
Faverjon C, Vial F, Andersson MG, Lecollinet S, Leblond A.West Nile virus (WNV) is a growing public health concern in Europe and there is a need to develop more efficient early detection systems. Nervous signs in horses are considered to be an early indicator of WNV and, using them in a syndromic surveillance system, might be relevant. In our study, we assessed whether or not data collected by the passive French surveillance system for the surveillance of equine diseases can be used routinely for the detection of WNV. We tested several pre-processing methods and detection algorithms based on regression. We evaluated system performances using simulate...
Löwen Levy Chalhoub F, Maia de Queiroz-Júnior E, Holanda Duarte B, Eielson Pinheiro de Sá M, Cerqueira Lima P, Carneiro de Oliveira A....In June 2019, a horse with neurological disorder was diagnosed with West Nile virus (WNV) in Boa Viagem, a municipality in the state of Ceará, northeast Brazil. A multi-institutional task force coordinated by the Brazilian Ministry of Health was deployed to the area for case investigation. A total of 513 biological samples from 78 humans, 157 domestic animals and 278 free-ranging wild birds, as well as 853 adult mosquitoes of 22 species were tested for WNV by highly specific serological and/or molecular tests. No active circulation of WNV was detected in vertebrates or mosquitoes by molecular...
Chaintoutis SC, Diakakis N, Papanastassopoulou M, Banos G, Dovas CI.Although experimental data regarding cross-protection of horse West Nile virus (WNV) vaccines against lineage 2 infections exist, the cross-protective efficacy of these vaccines under field conditions has not been demonstrated. This study was conducted to evaluate the capability of an inactivated lineage 1 vaccine (Equip WNV) to protect against natural infections from the Nea Santa-Greece-2010 lineage 2 strain. In total, 185 WNV-seronegative horses in Thessaloniki, Greece, were selected during 2 consecutive years (2011 and 2012); 140 were immunized, and 45 were used as controls. Horses were ex...
Rosas CT, Tischer BK, Perkins GA, Wagner B, Goodman LB, Osterrieder N.The immunogenicity in horses of a recombinant equine herpesvirus type 1 (EHV-1) vaccine expressing West Nile virus (WNV) prM and E proteins was studied. To construct the recombinant EHV-1, two-step en passant mutagenesis was employed for manipulation of a bacterial artificial chromosome (BAC) of vaccine strain RacH. Recombinant EHV-1 stably expressed the WNV prM and E proteins as demonstrated by indirect immunofluorescence and Western blotting. In addition, growth properties in vitro of the EHV-1/WNV recombinant were found to not be significantly different from those of the parental virus. To ...
Oliver J, Lukacik G, Kramer LD, Backenson PB, Sherwood JA, Howard JJ.In New York State (NYS), Eastern equine encephalitis (EEE) was first reported in a human in 1971, in horses in 1970, and in pheasants in 1952. Methods: Following work for the interval from 1970 to 1991, we identified cases in vertebrates from 1992 to 2012, through a passive surveillance system involving veterinarians in clinical practice, county health departments, and the Departments of Agriculture and Markets, Environmental Conservation, and Health, of the State of New York. Results: During an 11-year hiatus, from 1992 to 2002, no case in any vertebrate was observed. In a re-emergence, from ...
Ben Hassine T, Hammami S, Elghoul H, Ghram A.Two outbreaks of West Nile Fever (FWN) were observed in the Sahel of Tunisia in 1997 and 2003. Several cases of meningitis and meningoencephalitis have been described in humans during these two outbreaks. However, no animal or clinical findings or seroconversion have been detected despite a high seroprevalence in human beings found around the affected areas. Few data are available regarding the spreading of this virus in other parts of the country. The purpose of this study was to detect a possible WNV spread in horses in some areas of Tunisia considered to be at risk for WNV but which had not...
Efforts to detect West Nile virus (WNV) in the Vojvodina province, northern Serbia, commenced with human and mosquito surveillance in 2005, followed by horse (2009) and wild bird (2012) surveillance. The knowledge obtained regarding WNV circulation, combined with the need for timely detection of virus activity and risk assessment resulted in the implementation of a national surveillance programme integrating mosquito, horse and bird surveillance in 2014. From 2013, the system showed highly satisfactory results in terms of area specificity (the capacity to indicate the spatial distribution of t...
Ward MP, Scheurmann JA.Cases of human and equine West Nile virus (WNV) disease reported in Texas in 2002 were analyzed to assess their temporal relationship. For each human case with a known residential location, the closest equine case (within a 5 km radius) was selected. A total of 80 human-equine case pairs were identified, 51 (64%) of which were located in urban areas. Dates-of-onset of human and equine cases were positively correlated (r(SP)=0.494, P<0.001). Although overall there was no significant (P=0.207) difference between the dates-of-onset of human and equine cases, in urban areas of Texas equine case...
