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.
Minke JM, Siger L, Cupillard L, Powers B, Bakonyi T, Boyum S, Nowotny N, Bowen R.The emergence of lineage 2 strains of WNV in Europe as a cause of clinical disease and mortality in horses raised the question whether the existing WNV vaccines, all based on lineage 1 strains, protect against circulating lineage 2 strains of WNV. In the present paper we have determined the level of cross protection provided by the recombinant ALVAC(®)-WNV vaccine in a severe challenge model that produces clinical signs of WNV type 2 disease. Ten horses were vaccinated twice at 4 weeks interval with one dose of the ALVAC-WNV vaccine formulated at the minimum protective dose. A further 10 hors...
Franson JC, Hofmeister EK, Collins GH, Dusek RJ.We screened 1,397 feral horses (Equus caballus) on Sheldon National Wildlife Refuge, Nevada, United States, for IgM and IgG against flavivirus during 2004-2006, 2008, and 2009. Positive serum samples were tested for neutralizing antibodies to West Nile virus (WNV) and St. Louis encephalitis virus (SLEV). One animal was positive for antibody against WNV in 2004, but all others tested in 2004-2006 were negative. In 2008 and 2009, we found evidence of increasing seropositive horses with age, whereas seroprevalence of WNV decreased from 19% in 2008 to 7.2% in 2009. No horses were positive for anti...
Kutasi O, Bakonyi T, Lecollinet S, Biksi I, Ferenczi E, Bahuon C, Sardi S, Zientara S, Szenci O.The spread of lineage 2 West Nile virus (WNV) from sub-Saharan regions to Europe and the unpredictable change in pathogenicity indicate a potential public and veterinary health threat and requires scientific awareness. Objective: To describe the results of clinical and virological investigations of the 1st outbreak of a genetic lineage 2 WNV encephalomyelitis in horses. Methods: Seventeen horses with neurologic signs. Methods: Information regarding signalment, clinical signs, and outcome was obtained for each animal. Serology was performed in 15 cases, clinicopathological examination in 7 case...
West Nile virus (WNV), the most widely distributed flavivirus worldwide, has lately reemerged in Europe, causing worrisome outbreaks in humans and horses. Serological analysis by enzyme-linked immunoassay and plaque reduction neutralization test showed for the first time in Serbia that 12% of 349 horses presented specific neutralizing WNV antibodies, which in one case also cross-neutralized Usutu virus (USUV). This is the first time that anti-USUV high neutralizing antibody titers are reported in horses. All these data indicate that WNV and USUV are circulating in the region and advise on the ...
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.
Ahmadnejad F, Otarod V, Fallah MH, Lowenski S, Sedighi-Moghaddam R, Zavareh A, Durand B, Lecollinet S, Sabatier P.We report the first large-scale serosurvey for West Nile virus (WNV) conducted in the equine population in Iran. Blood samples were obtained in 2008-2009 from 1054 equines collected from 260 districts located in 27 provinces. The overall seroprevalence rate for WNV neutralizing antibodies was 23·7%. Marked geographical variations were observed as province-specific seroprevalence rates ranged from 1% to 88%, the highest values being observed in the southern and western parts of the country. The presence of IgM-positive animals (n=9) indicated a recent circulation of WNV in several provinces. L...
Recent outbreaks of equine infectious anaemia and equine viral arteritis in the UK. Update on the equine infectious anaemia situation in Europe. West Nile virus reported in several Mediterranean countries. Current and future approaches to equine viral arteritis control in the UK. These are among matters discussed in the quarterly equine disease surveillance report for April to June 2010, prepared by Defra, the Animal Health Trust and the British Equine Veterinary Association.
Kitai Y, Shirafuji H, Kanehira K, Kamio T, Kondo T, Konishi E.West Nile virus (WNV) and Japanese encephalitis (JE) virus are distributed separately in the world with some exceptions. There is a concern that WNV may invade into Asia where JE virus exists. On and after such invasion, any differential diagnosis could be complicated by serological crossreactivities. We previously demonstrated experimentally using horses infected with WNV that preimmunization with inactivated JE vaccine considerably affected the ability of neutralization tests and immunoglobulin M (IgM) antibody-capture enzyme-linked immunosorbent assay (ELISA) to diagnose WNV infection. Here...
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 ...
Murray KO, Mertens E, Despres P.Zoonotic West Nile virus (WNV) circulates in natural transmission cycles involving certain mosquitoes and birds, horses, humans, and a range of other vertebrates are incidental hosts. Clinical infections in humans can range in severity from uncomplicated WNV fever to fatal meningoencephalitis. Since its introduction to the Western Hemisphere in 1999, WNV had spread across North America, Central and South America and the Caribbean, although the vast majority of severe human cases have occurred in the United States of America (USA) and Canada. By 2002-2003, the WNV outbreaks have involved thousa...
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...
Venter M, Swanepoel R.West Nile virus (WNV) is widely distributed in South Africa, but since a few cases of neurological disease have been reported from this region, endemic lineage 2 strains were postulated to be of low virulence. Several cases of nonfatal encephalitis in humans as well as fatal cases in a foal, dog, and ostrich chicks have, however, been associated with lineage 2 WNV in South Africa. The pathogenesis of lineage 2 WNV strains was investigated using mouse neuroinvasive experiments, gene expression experiments, and genome sequence comparisons which indicated that lineage 2 strains that are highly 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...
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....
West Nile virus (WNV) was first detected in the Western Hemisphere in 1999 in New York City and has since caused seasonal epidemics of febrile illness and neurologic disease across the United States, where it is now the leading cause of arboviral encephalitis. This report updates a previous report and summarizes WNV activity in the United States reported to CDC in 2009. A total of 38 states and the District of Columbia (DC) reported 720 cases of WNV disease. Of these, 33 states and DC reported 386 cases of WNV neuroinvasive disease, for an incidence of 0.13 per 100,000 population. The five sta...
Phoutrides E, Jusino-Mendez T, Perez-Medina T, Seda-Lozada R, Garcia-Negron M, Davila-Toro F, Hunsperger E.After the isolation of West Nile virus (WNV) from humans, mosquitoes, and chickens in 2007, an analysis of animal surveillance involving multiple species (horses, monkeys, sheep, dogs, and birds) used to track WNV transmission from 2006 to 2008 was performed. During this period 13.4% of all the animal samples collected were seropositive by blocking ELISA for WNV. The most complete island-wide sampling was obtained from horses of which 22% were serologically positive and 96% were confirmed as WNV infections by plaque-reduction neutralization test. Our conclusion from this 3-year study is that a...
Petersson KH, Burr DB, Gomez-Chiarri M, Petersson-Wolfe CS.Horses have an increased susceptibility to infection because of a decline in immune function with advancing age. Vitamin E has been found to play a key role in normal immune system function. The purpose of the study was to examine the effect of vitamin E supplementation on immune function and response to vaccination in older horses. Predominantly older horses (18.9 +/- 1.3 yr, range 7 to 26 yr; 523 +/- 38 kg of BW) were supplemented orally once daily for 16 wk with either all-rac-alpha-tocopheryl acetate (15 IU/kg of BW; n = 8) or a placebo (n = 8). One horse from each group was removed from t...
Rios JJ, Fleming JG, Bryant UK, Carter CN, Huber JC, Long MT, Spencer TE, Adelson DL.West Nile virus, first identified within the United States in 1999, has since spread across the continental states and infected birds, humans and domestic animals, resulting in numerous deaths. Previous studies in mice identified the Oas1b gene, a member of the OAS/RNASEL innate immune system, as a determining factor for resistance to West Nile virus (WNV) infection. A recent case-control association study described mutations of human OAS1 associated with clinical susceptibility to WNV infection. Similar studies in horses, a particularly susceptible species, have been lacking, in part, because...
Angelini P, Tamba M, Finarelli AC, Bellini R, Albieri A, Bonilauri P, Cavrini F, Dottori M, Gaibani P, Martini E, Mattivi A, Pierro AM, Rugna G....Following a large West Nile virus (WNV) epidemic in northeastern Italy in 2008, human and animal surveillance activities were implemented in Emilia Romagna. Human surveillance was performed by serology or genome detection on blood and cerebrospinal fluid for all suspected cases suffering from acute meningoencephalitis in the regional territory. Animal surveillance consisted of passive and active surveillance of horses and active surveillance of wild birds and mosquitoes. Between 15 June and 31 October 2009, nine of 78 possible cases of West Nile neuroinvasive disease were confirmed (three fata...
Kitai Y, Kondo T, Konishi E.A complement-dependent cytotoxicity (CDC) assay was established to measure antibodies to the West Nile virus (WNV) nonstructural protein 1 (NS1) in horses. Sera collected from a WNV-infected horse mediated lysis of WNV NS1-expressing cells in a dose-dependent manner at higher percentages than sera from a Japanese encephalitis virus (JEV)-infected horse. The percentages of specific lysis for sera diluted 1:10 to 1:80 were <19.8% (assay cutoff) for almost all of the 100 JEV-infected or uninfected horses tested, in contrast to 55 to 76% in WNV-infected horses. Experimental infection revealed t...
Chevalier V, Dupressoir A, Tran A, Diop OM, Gottland C, Diallo M, Etter E, Ndiaye M, Grosbois V, Dia M, Gaidet N, Sall AA, Soti V, Niang M.In 2005, a serological study was carried out on horses in five ecologically contrasted zones of the Senegal River basin (Senegal) to assess West Nile virus (WNV) transmission and investigate underlying environmental risk factors. In each study zone, horses were randomly selected and blood samples taken. A land-cover map of the five study areas was built using two satellite ETM+ images. Blood samples were screened by ELISA for anti-WNV IgM and IgG and positive samples were confirmed by seroneutralization. Environmental data were analysed using a principal components analysis. The overall IgG se...
Martina BE, Koraka P, Osterhaus AD.West Nile virus (WNV) is a neurotropic Flavivirus that was associated with sporadic outbreaks of meningoencephalitis in Africa and the Middle East until 1999, when a more virulent strain emerged in the US that caused thousands of infections among humans and horses, with reported fatality rates between 10 and 50%. Although the epidemiology of WNV is changing into a more endemic pattern in the US, and the incidence of neuroinvasive disease is decreasing, the long-term effects of resolved WNV infections in humans, characterized as persistent movement disorders and various functional disabilities,...
Loroño-Pino MA, Farfan-Ale JA, Garcia-Rejon JE, Lin M, Rosado-Paredes E, Puerto FI, Bates A, Root JJ, Franklin AB, Sullivan HJ, Blitvich BJ.No abstract available
Zoonoses and public healthDecember 23, 2009
Volume 57, Issue 3 211-219 doi: 10.1111/j.1863-2378.2009.01303.x
Calistri P, Giovannini A, Savini G, Monaco F, Bonfanti L, Ceolin C, Terregino C, Tamba M, Cordioli P, Lelli R.After 10 years, West Nile virus (WNV) re-emerged in Italy in August 2008. As on 31 December 2008, the infection affected eight Provinces in three Regions (Emilia Romagna, Veneto, Lombardy), where a total of 794 cases of WNV infection in 251 equine stables were detected on the basis of the clinical signs and as a result of a serological screening in horses living in the area. Only 4.0% (32/794) of the serologically positive animals showed clinical signs, and the 32 clinical cases were reported in 18 different farms. The observed case-fatality rate was 15.6% (5/32). The confirmed clinical cases ...
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...
Rios LM, Sheu JJ, Day JF, Maruniak JE, Seino K, Zaretsky H, Long MT.The objective of this study was to examine the extrinsic risk factors of West Nile virus (WNV) clinical disease in Florida horses as established from confirmed and negative horses tested within the state from 2001 to 2003. An Arboviral Case Information Form (ACF) was submitted by a referring veterinarian at the time of testing to the Florida Department of Agriculture and Consumer Services on every horse suspected of a viral encephalitis in Florida. A follow-up survey that focused on arbovirus prevention and farm ecology was created and mailed to the owner of each tested horse. Data from the fo...
Pradel J, Chalvet Monfray K, Molia S, Vachiéry N, Rousteau A, Imbert D, Martinez D, Sabatier P, Lefrançois T.In Guadeloupe, West Nile virus (WNV) activity was first observed in equids in 2002, and a high seroprevalence was found in 2003. The objective of our study was to determine individual and environmental factors associated with the risk of WNV seropositivity during 2002-2003. Fieldwork was conducted to retrospectively determine the location of equids at the time of virus circulation and to collect information regarding environmental and individual variables. Sera were collected from 369 equids out of an estimated total population of less than 500. Thirty-four environmental and individual variabl...
Defilippo F, Dottori M, Lelli D, Chiari M, Cereda D, Farioli M, Chianese R, Cerioli MP, Faccin F, Canziani S, Trogu T, Sozzi E, Moreno A, Lavazza A....In Italy, the West Nile Virus surveillance plan considers a multidisciplinary approach to identify the presence of the virus in the environment (entomological, ornithological, and equine surveillance) and to determine the risk of infections through potentially infected donors (blood and organ donors). The costs associated with the surveillance program for the Lombardy Region between 2014 and 2018 were estimated. The costs of the program were compared with a scenario in which the program was not implemented, requiring individual blood donation nucleic acid amplification tests (NAT) to detect th...
Hernández-Jover M, Roche S, Ward MP.Vector-borne diseases can have substantial impacts on human and animal health, including major epidemics. West Nile virus (WNV) is of particular international importance due to its recent emergence and impact in the Western Hemisphere. Despite the presence of a sub-type of WNV (Kunjin virus, KUN) in Australia, a potential ecological niche could be occupied by an exotic strain of WNV of the North American type. This study assesses the probability an exotic strain of WNV enters Australia via an infected mosquito in an aircraft from the United States (U.S.) landing at Sydney airport, the probabil...
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...
Ward MP, Ramsay BH, Gallo K.Data from an outbreak (August to October, 2002) of West Nile virus (WNV) encephalomyelitis in a population of horses located in northern Indiana was scanned for clusters in time and space. One significant (p = 0.04) cluster of case premises was detected, occurring between September 4 and 10 in the south-west part of the study area (85.70 degrees N, 45.50 degrees W). It included 10 case premises (3.67 case premises expected) within a radius of 2264 m. Image data were acquired by the Advanced Very High Resolution Radiometer (AVHRR) sensor onboard a National Oceanic and Atmospheric Administration...
Cui J, Zhao Y, Wang H, Qiu B, Cao Z, Li Q, Zhang Y, Yan F, Jin H, Wang T, Sun W, Feng N, Gao Y, Sun J, Wang Y, Perlman S, Zhao J, Yang S, Xia X.West Nile virus (WNV) is prevalent in Africa, Europe, the Middle East, West Asia, and North America, and causes epidemic encephalitis. To date, no effective therapy for WNV infection has been developed; therefore, there is urgent need to find an efficient method to prevent WNV disease. In this study, we prepared and evaluated the protective efficacy of immune serum IgG and pepsin-digested F(ab')₂ fragments from horses immunized with the WNV virus-like particles (VLP) expressing the WNV M and E proteins. Immune equine F(ab')₂ fragments and immune horse sera efficiently neutralized WNV infec...
Humphreys JM, Pelzel-McCluskey AM, Cohnstaedt LW, McGregor BL, Hanley KA, Hudson AR, Young KI, Peck D, Rodriguez LL, Peters DPC.Mosquito-borne West Nile virus (WNV) is the causative agent of West Nile disease in humans, horses, and some bird species. Since the initial introduction of WNV to the United States (US), approximately 30,000 horses have been impacted by West Nile neurologic disease and hundreds of additional horses are infected each year. Research describing the drivers of West Nile disease in horses is greatly needed to better anticipate the spatial and temporal extent of disease risk, improve disease surveillance, and alleviate future economic impacts to the equine industry and private horse owners. To help...
A cross-sectional study was conducted to assess the circulation and risk factors associated with West Nile virus (WNV) exposure in equine and wild bird populations following the largest epidemic outbreak ever reported in Spain. A total of 305 equids and 171 wild birds were sampled between November 2020 and June 2021. IgG antibodies against flaviviruses were detected by blocking enzyme-linked immunosorbent assay (bELISA) in 44.9% (109/243) and 87.1% (54/62) of unvaccinated and vaccinated equids, respectively. The individual seroprevalence in unvaccinated individuals (calculated on animals serop...
Gomes FA, Jansen AM, Machado RZ, Jesus Pena HF, Fumagalli MJ, Silva A, Alves BF, Roque ALR, Moraes Figueiredo LT.Arboviruses and protozoans can cause neurologic disorders in horses. In Brazilian Amazon, several horses presenting signs compatible with disorders caused by these infectious agents have been observed. To contribute to the knowledge of this epidemiological picture, we sought to construct a serological diagnostic panel for neurotrophic infectious agents in local horses. A total of 213 blood samples from horses were collected from 29 farms in three municipalities. Samples were evaluated and considered positive when they met the following criteria: titers ≥ 1:80 with the indirect fluorescent an...
Cabre O, Durand JP, Prangé A, Gomez J, Maurizi L, Tolou H, Davoust B.This study was carried out in 2003 to detected serological evidence of West Nile virus infection in 190 Army horses kept nearby French troops stationed in Southeast France and in Africa (Chad, Côte d'Ivoire and Senegal). Both IgG and IgM antibodies were searched for using an ELISA assay. Specifiity of IgG antibodies was determined by western blot and plaque reduction seroneutraization. Finding showed that 79% of the Army horses (n=96) tested in Africa presented specific IgG antibodies. All horses that were seropositive for IgG were seronegative for IgM. None of the Army horses (n=94) tested i...
Fehér O, Bakonyi T, Barna M, Nagy A, Takács M, Szenci O, Joó K, Sárdi S, Korbacska-Kutasi O.In the last decade in Hungary and the neighbouring countries, West Nile Neuroinvasive Disease (WNND) has been caused in dramatically increasing numbers by lineage 2 West Nile Virus (WNV) strains both in horses and in humans. The disease in this geographical region is seasonal, so vaccination of horses should be carefully scheduled to maintain the highest antibody titres during outbreak periods. The objective of this study was to characterise the serum neutralising (SN) antibody titres against a lineage 2 WNV strain in response to vaccination with an inactivated lineage 1 vaccine (Equip® WNV)....
Choi KS, Ko YJ, Nah JJ, Kim YJ, Kang SY, Yoon KJ, Joo YS.A rapid immunoassay for detecting and quantifying West Nile virus (WNV)-neutralizing antibodies in sera was developed as an alternative to the plaque reduction neutralization test (PRNT), the gold standard test for WNV. The assay is a competitive, enzyme-linked immunosorbent assay using neutralizing monoclonal antibody 5E8 (NT-ELISA). A cutoff percent inhibition (PI) value of 35% (mean PI plus 3 standard deviations), with a specificity of 99%, was established based on analysis of 246 serum samples from horses free of WNV. The NT-ELISA detected neutralizing antibodies in all sera collected 7 or...
Delcambre GH, Liu J, Streit WJ, Shaw GPJ, Vallario K, Herrington J, Wenzlow N, Barr KL, Long MT.West Nile virus (WNV), a mosquito borne member of the Flaviviridae, is one of the most commonly diagnosed agents of viral encephalitis in horses and people worldwide. Objective: A cassette of markers for formalin-fixed paraffin-embedded tissue and an archive of tissues from experimental infections in the horse were used to investigate the equine neuroimmune response to WNV meningoencephalomyelitis to phenotype the early response to WNV infection in the horse. Methods: Quantitative analysis using archived tissue from experimentally infected horses. Methods: The thalamus and hindbrain from 2 gro...
Zakhia R, Dupuis AP, Khodr F, Fadel M, Kramer LD, Haddad N.West Nile virus (WNV) has never been reported from Lebanon. Yet, this country is located on the flyway of migratory birds in the Middle East region. Serological screening was conducted to assess the potential circulation of this virus. Human, horse, and chicken sera were collected from the Bekaa and North districts. Specific IgG and IgY were first screened by ELISA. Then, positive samples were confirmed by plaque reduction neutralization test (PRNT). Besides this, adult mosquitoes were collected and tested for the presence of WNV RNA using conventional RT-PCR. Sera screening revealed a seropre...
Metz MBC, Olufemi OT, Daly JM, Barba M.There is some evidence that West Nile virus (WNV), which causes encephalomyelitis in equids, is an emerging disease in Europe. The aim of this study was to perform a systematic review and meta-analysis to analyse seroprevalence studies of WNV in equids in European countries between 2001 and 2018. Two electronic databases, PubMed and Scopus, were searched for relevant publications published from 2001 to 2018 using predetermined keywords. A total of 1,484 papers were initially found. After applying the eligibility criteria, 39 papers were finally included in the systematic review. Analysis of 28...
Fehér OE, Fehérvári P, Tolnai CH, Forgách P, Malik P, Jerzsele Á, Wagenhoffer Z, Szenci O, Korbacska-Kutasi O.West Nile virus (WNV) is an emerging pathogen in Hungary, causing severe outbreaks in equines and humans since 2007. The aim of our study was to provide a comprehensive report on the clinical signs of West Nile neuroinvasive disease (WNND) in horses in Hungary. Clinical details of 124 confirmed equine WNND cases were collected between 2007 and 2019. Data about the seasonal and geographical presentation, demographic data, clinical signs, treatment protocols, and disease progression were evaluated. Starting from an initial case originating from the area of possible virus introduction by migrator...
Ward MP.Since first being detected in New York in 1999, West Nile virus (WNV) has spread throughout the United States and more than 20,000 cases of equine WNV encephalomyelitis have been reported. A spatial model of disease occurrence was developed, using data from an outbreak of serologically confirmed disease in an unvaccinated population of horses at 108 locations in northern Indiana between 3 August and 17 October 2002. Daily maximum temperature data were recorded at meteorological stations surrounding the study area. The distribution of the total number of degree-days elapsing between July 4 and ...
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...
Beckwith WH, Sirpenski S, French RA, Nelson R, Mayo D.The emergence of the West Nile virus (WNV) in the northeastern United States has drawn emphasis to the need for expanded arbovirus surveillance in Connecticut. Although the state of Connecticut began a comprehensive mosquito-screening program in 1997, only since 1999 have there been efforts to determine the prevalence of arboviruses in bird populations in this state. Herein, we report on our results of an arbovirus survey of 1,704 bird brains. Included in this report are the first known isolations of eastern equine encephalitis virus (EEEV) from crows and data on the geographic and temporal di...
Ibarra-Juarez L, Eisen L, Bolling BG, Beaty BJ, Blitvich BJ, Sanchez-Casas RM, Ayala-Sulca YO, Fernandez-Salas I.In the last 5 years, there has been only one reported human case of West Nile virus (WNV) disease in northern Mexico. To determine if the virus was still circulating in this region, equine and entomological surveillance for WNV was conducted in the state of Nuevo Leon in northern Mexico in 2006 and 2007. A total of 203 horses were serologically assayed for antibodies to WNV using an epitope-blocking enzyme-linked immunosorbent assay (bELISA). Seroprevalences for WNV in horses sampled in 2006 and 2007 were 26% and 45%, respectively. Mosquito collections in 2007 produced 7365 specimens represent...
Mongoh MN, Khaitsa ML, Dyer NW.West Nile virus (WNV) outbreak in North Dakota in 2002 included over 569 horse cases, clustered mainly in the eastern and northeastern parts of the state. The pattern of occurrence observed suggested existence of specific environmental and ecological factors that increased the risk for infection and illness in those locations. We developed a predictive model with factors that explained the pattern of WNV occurrence observed. Results indicated that surface elevation, temperature, precipitation, reported WNV-positive birds, reported WNV-positive humans, and reported WNV-positive mosquitoes were ...
Hébert L, Polledo G, Lecouturier F, Giorgi M, Beck C, Lowenski S, Laroucau K, Büscher P, Hans A, Becù T.Northern Argentina hosts equine populations living under preserved natural areas and extensive breeding conditions, with limited access to veterinary care. Horses can be in contact with i) wildlife considered to be a potential reservoir of horse pathogens (e.g. capybara, coatis and pampas deer) and/or ii) potential disease vectors such as ticks, horse flies, Culicidae and vampire bats. In this context, the aim of this study was to assess the exposure of horses from a herd in northern Argentina to different vector-borne pathogens. Serum samples were collected from 20 horses on a farm in Chaco p...
Lan DL, Wang CS, Deng B, Zhou JP, Cui L, Tang C, Yue H, Hua XG.West Nile virus (WNV) infection is an emerging zoonosis that threatens global public health. In this study, a total of 95 bird serum samples from 14 species and 341 horse serum samples were collected from 2008 to 2010 in Shanghai, China. All serum samples were screened initially for WNV-reactive antibodies using a competitive ELISA. The positive samples detected by ELISA were further confirmed using a plaque-reduction neutralization test (PRNT) for WNV and its most closely related flaviviruses in the area to avoid false positives due to cross-reactivity. Five (5·3%) of the bird serum samples ...
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...
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...
Fall AG, Diaïté A, Etter E, Bouyer J, Ndiaye TD, Konaté L.Active catches of adult females of Aedes vexans arabiensis Patton, (Diptera: Culicidae) Patton by nets or aspirator, were conducted in 2003 and 2004 in the vegetation at the edge of temporary ponds in Barkedji, Senegalese Ferlo area. Two hundred and forty-one engorged females were captured, dissected and the gut content adsorbed on a Whatman filter paper and analysed using the enzyme-linked immunosorbent assay (ELISA) technique to determinate the bloodmeal origin. Results indicated that Ae v. arabiensis fed primarily on mammals, including horses (35.7% of the bloodmeals), but also on birds (10...
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...
MacLachlan NJ, Balasuriya UB, Davis NL, Collier M, Johnston RE, Ferraro GL, Guthrie AJ.Viral diseases constitute an ever growing threat to the horse industry worldwide because of the rapid movement of large numbers of horses for competition and breeding. A number of different types of vaccines are available for protective immunization of horses against viral diseases. Traditional inactivated and live-attenuated (modified live virus, MLV) virus vaccines remain popular and efficacious but recombinant vaccines are increasingly being developed and used, in part because of the perceived deficiencies of some existing products. New generation vaccines include MLVs with deletions and/or...
Weissenböck H, Hubálek Z, Halouzka J, Pichlmair A, Maderner A, Fragner K, Kolodziejek J, Loupal G, Kölbl S, Nowotny N.Avian mortality and encephalomyelitis in equines are considered good indicators for West Nile virus (WNV) activity. We retrospectively tested 385 horse sera for WNV antibodies and looked for WNV nucleic acid and/or WNV antigen in paraffin embedded tissues from 12 horses with aetiologically unresolved encephalomyelitis and 102 free-living birds of different species which had been found dead. With the exception of four horses originating from eastern European countries investigated on the occasion of transit through Austria, all horse sera were negative. Nested RT-PCR of the horse tissues yielde...
