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.
Sewgobind S, McCracken F, Schilling M.West Nile virus (WNV) is a positive-sense single-stranded RNA virus belonging to the Flaviviridae family and is maintained in an enzootic cycle between avian hosts and mosquito vectors. Humans, horses and other mammals are susceptible to infection but are dead-end hosts due to a low viraemia. The disease can manifest itself in a variety of clinical signs and symptoms in people and horses from mild fever to severe encephalitis and morbidity. There are no vaccines licensed for human protection, but parts of Europe, North America, Africa and Australia have vaccines commercially available for hors...
Gonzálvez M, Franco JJ, Barbero-Moyano J, Caballero-Gómez J, Ruano MJ, Martínez R, Cano-Terriza D, García-Bocanegra I.The largest epidemic of West Nile virus (WNV) reported ever in Spain in both humans and equines occurred in 2020, affecting 77 humans and 139 equine herds. Here, we aimed to monitor the outbreaks detected in equid herds in Andalusia (southern Spain), the Spanish region where 89.9% of the outbreaks were reported, and to evaluate the virus circulation and risk factor associated with WNV exposure in the affected herds. The first WNV case was detected in mid-July 2020, the number of outbreaks peaked in mid-August and the last one was confirmed on 26th October 2020. WNV lineage 1 was detected in 12...
Mohammed MN, Yasmin AR, Ramanoon SZ, Noraniza MA, Ooi PT, Ain-Najwa MY, Natasha JA, Nur-Fazila SH, Arshad SS, Mohammed HO.West Nile virus is a mosquito-borne neurotropic pathogen with a wide host range that constitutes a significant risk to public and animal health. There is limited information on WNV infection in domesticated mammals in Malaysia; however, current reports indicate infections in birds, macaques, bats and pigs from Malaysia. In this study, 203 serum samples from cattle, goats, and horses were tested for the presence of anti-WNV IgG using a competitive enzyme-linked immunosorbent assay (c-ELISA). Additionally, using one-step RT-PCR, nasopharyngeal swabs were analyzed for WNV RNA from all 203 animals...
Magallanes S, Llorente F, Ruiz-López MJ, Martínez-de la Puente J, Soriguer R, Calderon J, Jímenez-Clavero MÁ, Aguilera-Sepúlveda P, Figuerola J.West Nile virus (WNV) is a re-emerging zoonotic pathogen with increasing incidence in Europe, producing a recent outbreak in 2020 in Spain with 77 human cases and eight fatalities. However, the factors explaining the observed changes in the incidence of WNV in Europe are not completely understood. Longitudinal monitoring of WNV in wild animals across Europe is a useful approach to understand the eco-epidemiology of WNV in the wild and the risk of spillover into humans. However, such studies are very scarce up to now. Here, we analysed the occurrence of WNV and Usutu virus (USUV) antibodies in ...
Hassanien RT, Hussein HA, Abdelmegeed HK, Abdelwahed DA, Khattab OM, Ali MH, Habashi AR, Ibraheem EM, Shahein MA, Abohatab EM.Due to climatic changes, arthropod-borne viruses have become a global health concern. In Egypt, West Nile virus (WNV) was initially detected in humans in 1950 and then in 1951, 1954, 1968, and 1989. Although WNV infection has been recorded in numerous Middle Eastern countries, its prevalence among the equine population in Egypt is unknown. This study aimed to investigate the current situation of vector-borne WNV in Egypt, estimate its seroprevalence, and assess the associated risk factors. Unassigned: We screened 1100 sera samples and nasal swabs from the same equids, 156 mosquito pools, and 3...
Schwarz ER, Long MT.West Nile virus (WNV) neuroinvasive disease threatens the health and well-being of horses and humans worldwide. Disease in horses and humans is remarkably similar. The occurrence of WNV disease in these mammalian hosts has geographic overlap with shared macroscale and microscale drivers of risk. Importantly, intrahost virus dynamics, the evolution of the antibody response, and clinicopathology are similar. The goal of this review is to provide a comparison of WNV infection in humans and horses and to identify similarities that can be exploited to enhance surveillance methods for the early dete...
Anderson C, Baha H, Boghdeh N, Barrera M, Alem F, Narayanan A.Zoonotic pathogens that are vector-transmitted have and continue to contribute to several emerging infections globally. In recent years, spillover events of such zoonotic pathogens have increased in frequency as a result of direct contact with livestock, wildlife, and urbanization, forcing animals from their natural habitats. Equines serve as reservoir hosts for vector-transmitted zoonotic viruses that are also capable of infecting humans and causing disease. From a One Health perspective, equine viruses, therefore, pose major concerns for periodic outbreaks globally. Several equine viruses ha...
Gothe LMR, Ganzenberg S, Ziegler U, Obiegala A, Lohmann KL, Sieg M, Vahlenkamp TW, Groschup MH, Hörügel U, Pfeffer M.Since 2018, autochthonous West Nile virus (WNV) infections have been regularly reported in eastern-central Germany. While clinically apparent infections in humans and horses are not frequent, seroprevalence studies in horses may allow the tracing of WNV and related flaviviruses transmission, such as tick-borne encephalitis virus (TBEV) and Usutu virus (USUV), and consequently help to estimate the risk of human infections. Hence, the aim of our study was to follow the seropositive ratio against these three viruses in horses in Saxony, Saxony Anhalt, and Brandenburg and to describe their geograp...
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...
Sánchez-Pacheco UA, Bahena-Mondragón BM, Hernández-Piedras FR, Soria-Osorio R, Meneses-Acosta A.The immunotherapy agents derived from horses are biological products that allow the neutralization of clinically relevant immunogens, such as the SARS-CoV-2 virus that causes COVID-19, or the neutralization of toxins present in the venoms of snakes, spiders, and other poisonous animals. Due to their importance, detecting adventitious viruses in equine hyperimmune serum (raw material in industrial processes) is a critical step to support the safety of products for human use, and, in consequence, it is a requirement for commercialization and distribution. The safety of the finished product is ba...
M'ghirbi Y, Mousson L, Moutailler S, Lecollinet S, Amaral R, Beck C, Aounallah H, Amara M, Chabchoub A, Rhim A, Failloux AB, Bouattour A.Mosquito-borne diseases have a significant impact on humans and animals and this impact is exacerbated by environmental changes. However, in Tunisia, surveillance of the West Nile virus (WNV) is based solely on the surveillance of human neuroinvasive infections and no study has reported mosquito-borne viruses (MBVs), nor has there been any thorough serological investigation of anti-MBV antibodies in horses. This study therefore sought to investigate the presence of MBVs in Tunisia. Among tested mosquito pools, infections by WNV, Usutu virus (USUV), and Sindbis virus (SINV) were identified in ....
García-Romero C, Carrillo Bilbao GA, Navarro JC, Martin-Solano S, Saegerman C.Arthropod-borne viruses (arboviruses) are a diverse group of ribonucleic acid (RNA) viruses, with the exception of African swine fever virus, that are transmitted by hematophagous arthropods to a vertebrate host. They are the important cause of many diseases due to their ability to spread in different environments and their diversity of vectors. Currently, there is no information on the geographical distribution of the diseases because the routes of transmission and the mammals (wild or domestic) that act as potential hosts are poorly documented or unknown. We conducted a systematic review fro...
Luethy D.The continued recognition and emergence of alphavirus and flavivirus diseases is a growing veterinary and public health concern. As the global environment continues to change, mosquito-borne diseases will continue to evolve and expand. Continued development of readily available vaccines for the prevention of these diseases in humans and animals is essential to controlling epizootics of these diseases. Further research into effective antiviral treatments is also sorely needed. This article describes equine encephalitis viruses with a focus on clinical and public health considerations.
Ruiz-López MJ, Muñoz-Chimeno M, Figuerola J, Gavilán AM, Varona S, Cuesta I, Martínez-de la Puente J, Zaballos Á, Molero F, Soriguer RC....Emerging infectious diseases are one of the most important global health challenges because of their impact on human and animal health. The vector-borne West Nile virus (WNV) is transmitted between birds by mosquitos, but it can also infect humans and horses causing disease. The local circulation of WNV in Spain has been known for decades, and since 2010, there have been regular outbreaks in horses, although only six cases were reported in humans until 2019. In 2020, Spain experienced a major outbreak with 77 human cases, which was followed by 6 additional cases in 2021, most of them in the An...
Laabassi F, Dheilly N, Beck C, Amaral R, Gonzalez G, Gaudaire D, Madeline A, Lecouturier F, Lecollinet S, Zientara S, Hans A, Valle-Casuso JC.In order to determine the prevalence of equine infectious anemia virus (EIAV), Usutu virus (USUV), and West Nile virus (WNV) in eastern Algerian drylands, 340 sera from distinct equids have been collected from 2015 to 2017. Serological analysis for the presence of antibodies against EIAV and flaviviruses was performed using commercially available ELISAs. Sera detected positive, doubtful, or negative close to the doubtful threshold in flavivirus ELISA were tested by the virus neutralization test (VNT), using WNV and USUV strains. The prevalence of WNV antibodies with ELISA was 11.47% (39/340) a...
Musa-Gobe R, Omeiza G, Nafarnda W, Adamu A.West Nile virus (WNV) is an emerging arbovirus which affects humans and horses. A cross sectional study was carried out on 106 local horses in Kaduna and 78 domestic chickens in Federal Capital Territory. A total of 184 sera were screened for West Nile virus anti Pr‑E antibodies using ID Screen® West Nile competitive enzyme linked immunosorbent assay. For the horses, an overall prevalence of 92.45% was recorded while domestic chickens had a preponderance of 7.69%. From our study, there was a statistical significant difference between the occurrences of WNV in stallions than mares with p <...
Lohmann KL, Sieg M, Landmann M, Ganzenberg S, Arnold C, Vahlenkamp T, Ulrich RG.The presenting complaints, clinical signs, diagnostic evaluation, therapy, and outcome of 12 horses with clinically apparent West-Nile-Virus (WNV) infection are described. Methods: Case series RESULTS: The adult horses (age 6-18 years, 7 mares, 5 geldings) from Saxony and Saxony-Anhalt were presented with various clinical histories between September 2018 and September 2020. All horses were presented in August or September and no horse was vaccinated against WNV. Fever as the most common general clinical sign was present in 8/12 horses. The most common neurological signs were muscle fascicula...
Patroca da Silva S, Barbosa de Almeida Medeiros D, Ribeiro Cruz AC, Marques França AF, Diniz Nunes BT, Guerreiro Rodrigues DS, Pinto da Silva EV....In 2018, during the surveillance for West Nile virus (WNV) in horses with neurological clinical signs in the state of Espírito Santo (Brazil), 19 animals were investigated, and 52 biological samples were collected for WNV diagnostic. One brain sample was positive for WNV by RT-qPCR and the virus was isolated in C6/36 cell culture and sequenced. We obtained a nearly complete genome of WNV co-infected with Peruvian horse sickness virus (PHSV) in the cell culture. After confirmation of PHSV by next-generation sequencing, a new PHSV RT-qPCR protocol was developed, which was used to detect another...
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...
Cavalleri JV, Korbacska-Kutasi O, Leblond A, Paillot R, Pusterla N, Steinmann E, Tomlinson J.Horses and other equids can be infected with several viruses of the family Flaviviridae, belonging to the genus Flavivirus and Hepacivirus. This consensus statement focuses on viruses with known occurrence in Europe, with the objective to summarize the current literature and formulate clinically relevant evidence-based recommendations regarding clinical disease, diagnosis, treatment, and prevention. The viruses circulating in Europe include West Nile virus, tick-borne encephalitis virus, Usutu virus, Louping ill virus and the equine hepacivirus. West Nile virus and Usutu virus are mosquito-bor...
Chalhoub FLL, Horta MAP, Alcantara LCJ, Morales A, Dos Santos LMB, Guerra-Campos V, Rodrigues CDS, Santos CC, Mares-Guia MAM, Pauvolid-Corrêa A....Infections with arboviruses are reported worldwide. Saint Louis encephalitis (SLEV) and West Nile (WNV) viruses are closely related flaviviruses affecting humans and animals. SLEV has been sporadically detected in humans, and corresponding antibodies have been frequently detected in horses throughout Brazil. WNV was first reported in western Brazil over a decade ago, has been associated with neurological disorders in humans and equines and its prevalence is increasing nationwide. Herein, we investigated by molecular and serological methods the presence of SLEV and WNV in equines from Rio de Ja...
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...
Figuerola J, Jiménez-Clavero MÁ, Ruíz-López MJ, Llorente F, Ruiz S, Hoefer A, Aguilera-Sepúlveda P, Jiménez-Peñuela J, García-Ruiz O....Reports of West Nile virus (WNV) associated disease in humans were scarce in Spain until summer 2020, when 77 cases were reported, eight fatal. Most cases occurred next to the Guadalquivir River in the Sevillian villages of Puebla del Río and Coria del Río. Detection of WNV disease in humans was preceded by a large increase in the abundance of in the neighbourhood of the villages where most human cases occurred. The first WNV infected mosquitoes were captured approximately one month before the detection of the first human cases. Overall, 33 positive pools of and one pool of were found. Se...
Molini U, Franzo G, Rautenbach I, Otto HV, Khaiseb S, Di Gennaro A, Ntahonshikira C, Baines I, Monaco F, Savini G, D'Alterio N.West Nile virus (WNV) is a vector-borne virus maintained in nature by a bird-mosquito cycle. However, it can occasionally and accidentally infect horses and human beings, leading to sometimes severe or even fatal outcomes in these species. Therefore, the monitoring of its circulation and disease occurrence is of relevance. Unfortunately, it is underdiagnosed or not diagnosed in several African counties, including Namibia, where no data is currently available for horses. In this study, 98 horses in three different stables in the Windhoek city area were investigated. They were found to have a se...
Fritsch H, Pereira FM, Costa EA, Fonseca V, Tosta S, Xavier J, Levy F, Oliveira C, Menezes G, Lima J, Santos L, Silva L, Nardy V, Astete MKG....During these past years, several studies have provided serological evidence regarding the circulation of West Nile virus (WNV) in Brazil. Despite some reports, much is still unknown regarding the genomic diversity and transmission dynamics of this virus in the country. Recently, genomic monitoring activities in horses revealed the circulation of WNV in several Brazilian regions. These findings on the paucity of genomic data reinforce the need for prompt investigation of WNV infection in horses, which may precede human cases of encephalitis in Brazil. Thus, in this study, we retrospectively scr...
Ganzenberg S, Sieg M, Ziegler U, Pfeffer M, Vahlenkamp TW, Hörügel U, Groschup MH, Lohmann KL.West Nile virus (WNV) infections were first detected in Germany in 2018, but information about WNV seroprevalence in horses is limited. The study's overall goal was to gather information that would help veterinarians, horse owners, and veterinary-, and public health- authorities understand the spread of WNV in Germany and direct protective measures. For this purpose, WNV seroprevalence was determined in counties with and without previously registered WNV infections in horses, and risk factors for seropositivity were estimated. The cohort consisted of privately owned horses from nine counties i...
Vasić A, Răileanu C, Körsten C, Vojinović D, Manić M, Urošević A, Nikolić N, Dulović O, Tews BA, Petrović T, Silaghi C, Valčić M....West Nile virus (WNV) is a zoonotic mosquito-borne virus classified as family Flaviviridae and genus Flavivirus. The first WNV outbreak in humans in the Republic of Serbia was recorded in 2012. Equids and dogs can show clinical symptoms after WNV infection and are often used as sentinels. This study aimed to (i) give insight into seropositivity for WNV in clinically healthy dog and horse sera in different regions of Serbia and (ii) compare diagnostic value of 'in-house' and commercially available indirect immunofluorescence (IFA) and enzyme-linked immunoassay (ELISA) tests to 'gold standard' v...
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...
Di Pol G, Crotta M, Taylor RA.Increases in temperature and extreme weather events due to global warming can create an environment that is beneficial to mosquito populations, changing and possibly increasing the suitable geographical range for many vector-borne diseases. West Nile Virus (WNV) is a flavivirus, maintained in a mosquito-avian host cycle that is usually asymptomatic but can cause primarily flu-like symptoms in human and equid accidental hosts. In rare circumstances, serious disease and death are possible outcomes for both humans and horses. The main European vector of WNV is the Culex pipiens mosquito. This stu...
Desanti-Consoli H, Bouillon J, Chapuis RJJ.Vaccination against infectious diseases is a cornerstone of veterinary medicine in the prevention of disease transmission, illness severity, and often death in animals. In North American equine medicine, equine vaccines protecting against tetanus, rabies, Eastern and Western equine encephalomyelitis, and West Nile are core vaccines as these have been classified as having a heightened risk of mortality, infectiousness, and endemic status. Some guidelines differ from the label of vaccines, to improve the protection of patients or to decrease the unnecessary administration to reduce potential sid...
Blitvich BJ, Bowen RA, Marlenee NL, Hall RA, Bunning ML, Beaty BJ.We evaluated the ability of epitope-blocking enzyme-linked immunosorbent assays (ELISAs) to detect West Nile virus (WNV) antibodies in domestic mammals. Sera were collected from experimentally infected horses, cats, and pigs at regular intervals and screened in ELISAs and plaque reduction neutralization tests. The diagnostic efficacies of these techniques were similar.
Huang ZY, de Boer WF, van Langevelde F, Olson V, Blackburn TM, Prins HH.Hosts species for multi-host pathogens show considerable variation in the species' reservoir competence, which is usually used to measure species' potential to maintain and transmit these pathogens. Although accumulating research has proposed a trade-off between life-history strategies and immune defences, only a few studies extended this to host species' reservoir competence. Using a phylogenetic comparative approach, we studied the relationships between some species' life-history traits and reservoir competence in three emerging infectious vector-borne disease systems, namely Lyme disease, W...
Seino KK, Long MT, Gibbs EP, Bowen RA, Beachboard SE, Humphrey PP, Dixon MA, Bourgeois MA.We used a severe challenge model that produces clinical West Nile virus (WNV) disease to test the efficacy of three commercially available equine WNV vaccines in horses. Twenty-four healthy, WNV-seronegative horses of varying ages and genders were placed, in random and blind manner, into three trial groups consisting of eight horses each; two horses in each group received (i) an inactivated WNV vaccine (K-WN), (ii) a modified-live vaccine (CP-WN) containing the WNV prM and E proteins expressed by a canarypox vector, (iii) a live-chimera vaccine (WN-FV) containing WNV prM and E proteins express...
Venter M, Human S, Zaayman D, Gerdes GH, Williams J, Steyl J, Leman PA, Paweska JT, Setzkorn H, Rous G, Murray S, Parker R, Donnellan C, Swanepoel R.Serologic evidence suggests that West Nile virus (WNV) is widely distributed in horses in southern Africa. However, because few neurologic cases have been reported, endemic lineage 2 strains were postulated to be nonpathogenic in horses. Recent evidence suggests that highly neuroinvasive lineage 2 strains exist in humans and mice. To determine whether neurologic cases are being missed in South Africa, we tested 80 serum or brain specimens from horses with unexplained fever (n = 48) and/or neurologic signs (n = 32) for WNV. From March 2007 through June 2008, using reverse transcription-PCR (RT-...
El Garch H, Minke JM, Rehder J, Richard S, Edlund Toulemonde C, Dinic S, Andreoni C, Audonnet JC, Nordgren R, Juillard V.Successful vaccination against West Nile virus (WNV) requires induction of both neutralizing antibodies and cell-mediated immune responses. In this study, we have assessed the ability of a recombinant ALVAC-WNV vaccine (RECOMBITEK WNV) to elicit neutralizing antibodies and virus-specific cell-mediated immune responses in horses. In addition, we examined whether prior exposure to ALVAC-WNV vaccine would inhibit B and cell-mediated immune responses against the transgene product upon subsequent booster immunizations with the same vaccine. The results demonstrated that the recombinant ALVAC-WNV va...
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...
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...
Cantile C, Del Piero F, Di Guardo G, Arispici M.The pathologic and peroxidase immunohistochemical features of West Nile flavivirus (WNV) infection were compared in four horses from the northeastern United States and six horses from central Italy. In all 10 animals, there were mild to severe polioencephalomyelitis with small T lymphocyte and lesser macrophage perivascular infiltrate, multifocal glial nodules, neutrophils, and occasional neuronophagia. Perivascular hemorrhages, also noted macroscopically in two animals, were observed in 50% of the horses. In the four American horses, lesions extended from the basal nuclei through the brain st...
García-Bocanegra I, Jaén-Téllez JA, Napp S, Arenas-Montes A, Fernández-Morente M, Fernández-Molera V, Arenas A.TO THE EDITOR: West Nile virus (WNV) is a member of the genus Flavivirus within the Japanese encephalitis antigenic complex. The enzootic virus cycle involves transmission between avian hosts and ornithophilic mosquitoes, whereas humans and horses are considered dead-end hosts. Given the recent increase of WNV infection in humans and horses in Europe, concern has been raised regarding public and animal health.
David S, Abraham AM.Since the isolation of West Nile virus (WNV) in 1937, in Uganda, it has spread globally, causing significant morbidity and mortality. While birds serve as amplifier hosts, mosquitoes of the Culex genus function as vectors. Humans and horses are dead end hosts. The clinical manifestations of West Nile infection in humans range from asymptomatic illness to West Nile encephalitis. Methods: The laboratory offers an array of tests, the preferred method being detection of RNA and serum IgM for WNV, which, if detected, confirms the clinical diagnosis. Although no definitive antiviral therapy and vacc...
Shirato K, Kimura T, Mizutani T, Kariwa H, Takashima I.West Nile (WN) virus is a mosquito-borne flavivirus that can cause lethal encephalitis in humans and horses. The WN virus endemic in New York City (NY) in 1999 caused large-scale mortality of wild birds that was not evident in endemic areas in other parts of the world, and the pathogenesis of the WN virus strain isolated in NY (NY strain) appears to differ from that of previously isolated strains. However, the pathogenesis of NY strain infection remains unclear. This study examined CC (RANTES/CCL5, MIP-1 alpha/CCL3, MIP-1 beta/CCL4) and CXC (IP-10/CXCL10, B lymphocyte chemoattractant (BLC/CXCL...
Schuffenecker I, Peyrefitte CN, el Harrak M, Murri S, Leblond A, Zeller HG.West Nile virus (WNV) reemerged in Morocco in September 2003, causing an equine outbreak. A WNV strain isolated from a brain biopsy was completely sequenced. On the basis of phylogenetic analyses, Moroccan WNV strains isolated during the 1996 and 2003 outbreaks were closely related to other strains responsible for equine outbreaks in the western Mediterranean basin.
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 ...
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...
Kulkarni MA, Berrang-Ford L, Buck PA, Drebot MA, Lindsay LR, Ogden NH.In Canada, the emergence of vector-borne diseases may occur via international movement and subsequent establishment of vectors and pathogens, or via northward spread from endemic areas in the USA. Re-emergence of endemic vector-borne diseases may occur due to climate-driven changes to their geographic range and ecology. Lyme disease, West Nile virus (WNV), and other vector-borne diseases were identified as priority emerging non-enteric zoonoses in Canada in a prioritization exercise conducted by public health stakeholders in 2013. We review and present the state of knowledge on the public heal...
Ostlund EN, Crom RL, Pedersen DD, Johnson DJ, Williams WO, Schmitt BJ.After the 1999 outbreak of West Nile (WN) encephalitis in New York horses, a case definition was developed that specified the clinical signs, coupled with laboratory test results, required to classify cases of WN encephalitis in equines as either probable or confirmed. In 2000, 60 horses from seven states met the criteria for a confirmed case. The cumulative experience from clinical observations and diagnostic testing during the 1999 and 2000 outbreaks of WN encephalitis in horses will contribute to further refinement of diagnostic criteria.
Baer A, Lundberg L, Swales D, Waybright N, Pinkham C, Dinman JD, Jacobs JL, Kehn-Hall K.Venezuelan equine encephalitis virus (VEEV) is a previously weaponized arthropod-borne virus responsible for causing acute and fatal encephalitis in animal and human hosts. The increased circulation and spread in the Americas of VEEV and other encephalitic arboviruses, such as eastern equine encephalitis virus and West Nile virus, underscore the need for research aimed at characterizing the pathogenesis of viral encephalomyelitis for the development of novel medical countermeasures. The host-pathogen dynamics of VEEV Trinidad donkey-infected human astrocytoma U87MG cells were determined by car...
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...
Minke JM, Siger L, Karaca K, Austgen L, Gordy P, Bowen R, Renshaw RW, Loosmore S, Audonnet JC, Nordgren B.An ALVAC (canarypoxvirus)-based recombinant (vCP2017) expressing the prM and E genes derived from a 1999 New York isolate of West Nile virus (WNV) was constructed and assessed for its protective efficacy in horses in two different experiments. In the first trial, a dose titration study was conducted to evaluate both serum neutralising antibody responses to WNV and duration of immunity. In the second trial the onset of protection was determined. Twenty-eight adult horses received two doses of vCP2017 administered intramuscularly at 5-week intervals and sixteen horses comprised age-matched non-v...
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...
Blitvich BJ, Fernandez-Salas I, Contreras-Cordero JF, Marlenee NL, Gonzalez-Rojas JI, Komar N, Gubler DJ, Calisher CH, Beaty BJ.Serum samples were obtained from 24 horses in the State of Coahuila, Mexico, in December 2002. Antibodies to West Nile virus were detected by epitope-blocking enzyme-linked immunosorbent assay and confirmed by plaque reduction neutralization test in 15 (62.5%) horses. We report the first West Nile virus activity in northern Mexico.
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...
Kampen H, Holicki CM, Ziegler U, Groschup MH, Tews BA, Werner D.In 2018, West Nile virus (WNV) broke out for the first time in Germany, with continuation of the epidemic in 2019, involving birds, horses and humans. To identify vectors and characterize the virus, mosquitoes were collected in both years in zoological gardens and on a horse meadow immediately following the diagnosis of disease cases in birds and horses. Mosquitoes were identified and screened for WNV by qRT-PCR, with virus-positive samples being sequenced for the viral envelope protein gene. While no positive mosquitoes were found in 2018, seven mosquito pools tested positive for WNV in 2019 ...
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...
Davidson AH, Traub-Dargatz JL, Rodeheaver RM, Ostlund EN, Pedersen DD, Moorhead RG, Stricklin JB, Dewell RD, Roach SD, Long RE, Albers SJ, Callan RJ....To compare neutralizing antibody response between horses vaccinated against West Nile virus (WNV) and horses that survived naturally occurring infection. Methods: Cross-sectional observational study. Methods: 187 horses vaccinated with a killed WNV vaccine and 37 horses with confirmed clinical WNV infection. Methods: Serum was collected from vaccinated horses prior to and 4 to 6 weeks after completion of an initial vaccination series (2 doses) and 5 to 7 months later. Serum was collected from affected horses 4 to 6 weeks after laboratory diagnosis of infection and 5 to 7 months after the first...
Pauvolid-Corrêa A, Morales MA, Levis S, Figueiredo LT, Couto-Lima D, Campos Z, Nogueira MF, da Silva EE, Nogueira RM, Schatzmayr HG.Despite evidence of West Nile virus (WNV) activity in Colombia, Venezuela and Argentina, this virus has not been reported in most South American countries. In February 2009, we commenced an investigation for WNV in mosquitoes, horses and caimans from the Pantanal, Central-West Brazil. The sera of 168 horses and 30 caimans were initially tested using a flaviviruses-specific epitope-blocking enzyme-linked immunosorbent assay (blocking ELISA) for the detection of flavivirus-reactive antibodies. The seropositive samples were further tested using a plaque-reduction neutralisation test (PRNT90) for ...
Figuerola J, Jiménez-Clavero MÁ, Ruíz-López MJ, Llorente F, Ruiz S, Hoefer A, Aguilera-Sepúlveda P, Jiménez-Peñuela J, García-Ruiz O....Reports of West Nile virus (WNV) associated disease in humans were scarce in Spain until summer 2020, when 77 cases were reported, eight fatal. Most cases occurred next to the Guadalquivir River in the Sevillian villages of Puebla del Río and Coria del Río. Detection of WNV disease in humans was preceded by a large increase in the abundance of in the neighbourhood of the villages where most human cases occurred. The first WNV infected mosquitoes were captured approximately one month before the detection of the first human cases. Overall, 33 positive pools of and one pool of were found. Se...
Jansen S, Heitmann A, Lühken R, Leggewie M, Helms M, Badusche M, Rossini G, Schmidt-Chanasit J, Tannich E.The continuous circulation of West Nile virus (WNV) in Central, South and East Europe and its recent detection in several dead birds and two horses in Germany highlights the need for information on WNV vector competence of mosquitoes from Central Europe. Therefore, three common Culex species (Culex pipiens biotype pipiens, Culex pipiens biotype molestus and Culex torrentium) from Germany were orally infected with WNV and kept at 18 °C, 21 °C, 24 °C or 27 °C for 14 or 21 days post infection (dpi). Thereafter viable WNV was present in the saliva in all tested taxa, but only at incubation tem...
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...
Bisanzio D, Giacobini M, Bertolotti L, Mosca A, Balbo L, Kitron U, Vazquez-Prokopec GM.West Nile Virus (WNV) transmission in Italy was first reported in 1998 as an equine outbreak near the swamps of Padule di Fucecchio, Tuscany. No other cases were identified during the following decade until 2008, when horse and human outbreaks were reported in Emilia Romagna, North Italy. Since then, WNV outbreaks have occurred annually, spreading from their initial northern foci throughout the country. Following the outbreak in 1998 the Italian public health authority defined a surveillance plan to detect WNV circulation in birds, horses and mosquitoes. By applying spatial statistical analysi...
