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Topic:West Nile Virus
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.
Increasing Seroprevalence In Horses Evidences Widespread Circulation Of West Nile Virus In Albania. West Nile virus (WNV) is a zoonotic mosquito-borne flavivirus that causes West Nile disease, an emerging and re-emerging infection of major global importance. Horses are an important sentinel species for monitoring WNV circulation. Since viraemia in horses is brief and viral loads in the blood are low, serological assays are the primary tools used to monitor WNV exposure. This study aimed to estimate the seroprevalence of WNV antibodies in horses in Albania. Between 2017 and 2020, 509 serum samples were collected from apparently healthy, unvaccinated horses across different regions of the coun...
First evidence of exposure to West Nile Virus in horses within Denmark, 2025. A nationwide serological screening of 822 horses was conducted in Autumn 2025 to investigate potential exposure to West Nile Virus (WNV) within Denmark. Serum samples were tested for antibodies against WNV, tick-borne encephalitis virus (TBEV) and Usutu virus (USUV). Four horses without any history of travel outside of Denmark, or previous vaccination against WNV, tested positive for WNV neutralising antibodies. The results support local exposure to WNV indicating that virus infected mosquitoes have been present in Denmark and underline the usefulness of horses as sentinels for the risk of hum...
West Nile Virus in Horses as a Sentinel Host in One Health Surveillance: Epidemiological Insights and Future Perspectives. West Nile virus (WNV) is a globally distributed mosquito-borne flavivirus with significant implications for both veterinary and public health. While horses are incidental dead-end hosts, their epidemiological role extends beyond clinical disease, as they can serve as effective sentinel hosts for detecting local viral circulation. Their frequent exposure to mosquito vectors, ability to mount measurable antibody responses, geographic stability, accessibility for monitoring, and the possibility of observation within managed owner-veterinarian systems make them particularly suitable for surveillan...
Seroprevalence of Orthoflaviviruses in horses in 3 different Algerian climatic zones between 2021 and 2023. Orthoflaviviruses are etiological agents of neurological diseases in equines. Horses are susceptible to equine Tick-borne encephalitis virus (TBEV), Usutu virus (USUV), and West Nile virus (WNV), although mostly WNV has been associated with clinical disease. The aim of the present study was to estimate the prevalence of TBEV, USUV and WNV in 289 healthy horses from nine provinces of Algeria. This study was conducted between March 2021 and December 2023. Sera that tested positive, doubtful, or negative close to the doubtful threshold in the Orthoflavivirus-ELISA were further tested by the virus...
Diagnosis and Surveillance of West Nile Virus Infection in Horses: Current Methods, Challenges, and Future Directions. West Nile virus (WNV) is a mosquito-borne flavivirus of growing importance for both human and equine health in Europe. Horses are highly susceptible to neurological disease and, because they share ecological exposure with humans, they represent valuable sentinels for detecting local viral circulation within a One Health framework. However, diagnosis of WNV infection in equines is complicated by the short and low-level viraemia, which limits the sensitivity of molecular assays, and by serological cross-reactivity with related flaviviruses and the confounding effects of vaccination. In this narr...
West Nile Virus in Europe: Epidemiology, Vector Ecology, Environmental Drivers, and the Role of Equine Sentinel Surveillance in a One Health Framework. West Nile virus (WNV) is a mosquito-borne flavivirus that remains an important public and veterinary health concern across Europe. Periodic outbreaks affecting humans, horses, and wildlife highlight the complex ecological interactions underlying viral circulation. This narrative review aims to synthesize current knowledge regarding WNV epidemiology, transmission dynamics, and surveillance strategies in Europe, with particular attention to the Romanian context. Available surveillance data indicate recurrent seasonal transmission in several European regions; however, reported case numbers may be...
Gaps Between Awareness and Prevention of West Nile Virus Among Horse Owners in an Endemic Country: A Cross-Sectional Study from Romania. West Nile virus (WNV) circulates endemically in Romania, yet prevention of WNV infection in horses largely depends on owner-driven decisions that require accurate risk perception and veterinary guidance. A cross-sectional online survey was carried out between May and November 2025 to evaluate the knowledge, attitudes, and preventive practices (KAP) regarding WNV among 227 horse owners from various Romanian regions. In total, 67.4% of respondents had previously heard of WNV. The main transmission route was correctly identified as mosquito bites by 49.8% of participants, while 32.2% answered "do...
Serological Investigations on West Nile Virus in Horses in Kazakhstan. This study presents the first investigation of West Nile virus (WNV) seroprevalence among farmed horses in Kazakhstan. In 2024, a total of 368 serum samples were collected from horses across 106 settlements in 10 regions of the Republic of Kazakhstan. Using an enzyme-linked immunosorbent assay (ELISA), antibodies to WNV were detected in 32 horses (8.7%; 95% CI: 6.2-12.0%) from six regions. Among the seropositive animals, 26 (81.25%) were females and 6 (18.75%) were males, ranging in age from 1 to 19 years. No statistically significant association between sex and the presence of antibodies to W...
Molecular and Serological Surveillance of Mosquito-Borne Viruses in Racehorses or Mosquitoes From Horse Farms in Shanghai, China, 2022. Getah virus (GETV), Japanese encephalitis virus (JEV), West Nile virus (WNV), and African horse sickness virus (AHSV) are mosquito-borne viruses threatening the health of racehorses. However, the systematic surveillance of these viruses among Shanghai racehorses remains lacking. Therefore, molecular and serological surveillance was conducted for these viruses in racehorses and mosquitoes at horse farms in Shanghai, China, during 2022 to assess their prevalence. Among 11,140 mosquitoes collected from seven farms across four districts, and were identified as the dominant species. RT-qPCR detec...
First report of West Nile virus infections in horses in Tunisia from 2018 to 2023. West Nile virus (WNV) is an arthropod borne virus, the most widely distributed of the encephalitic Orthoflaviviruses. It can cause severe neurological symptoms in both humans and horses. It poses an emerging threat to both public and animal health. In this study, we retrospectively screened 25 suspected WNV samples collected from 2018 to 2023. Methods: A total number of 25 samples (brain tissue and blood) were collected from clinically affected horses and those already deceased across several locations in Tunisia. All samples were tested for the presence of WNV NS2A gene using qRT-PCR. Eleven ...
Introduction of West Nile virus lineage 2 leads to neuroinvasive cases in humans and horses in Sicily, 2022-2023. In Italy, West Nile virus (WNV) has been consistently causing disease in humans, horses, and birds since 2008; it was initially confined to the northeast of the country and then spread gradually to the western and southern regions. WNV lineage 1 (WNV-L1) virus was the only lineage that circulated in Italy until 2011, but it was progressively replaced by WNV lineage 2 (WNV-L2). WNV disease in humans was not observed in Sicily, southern Italy, until 2016, when the first case of West Nile neuroinvasive disease (WNND) due to WNV-L1 was reported. Our results demonstrate the introduction of WNV-L2 i...
A retrospective study of 171 cases of equine meningoencephalomyelitis in the United States, 1996-2023. Equine meningoencephalomyelitis is an important cause of morbidity and mortality and is associated with a wide variety of infectious etiologies. Because of the lack of large retrospective studies, the prevalence and incidence of these diseases are unknown. Here we describe 171 cases of meningoencephalomyelitis in horses submitted to the Section of Anatomic Pathology at the New York State Animal Health Diagnostic Center (Cornell University, Ithaca, NY, USA) from 1996-2023. Neuroinflammatory disease was identified in 5.4% of submitted horses with a wide breed, age, and sex distribution. A parasi...
Immunohistochemical and molecular confirmation of West Nile Virus associated polioencephalomyelitis in a mule from Southern Brazil. West Nile fever is a zoonotic arboviral disease caused by the West Nile Virus (WNV), responsible for deaths in humans, mammals, and birds with associated neurological manifestations. All previous investigations of WNV from Brazil were based primarily on serological and molecular analyses and in humans, equids, and birds in the northern and southeastern regions of the country. This study describes the pathological and molecular findings observed in a mule, from the state of Paraná, southern Brazil, that died during an outbreak involving equids with clinical manifestations of a neurological dis...
West Nile virus in horses: surveillance, diagnosis and prevention in the UK. With the geographical distribution of West Nile virus expanding, there is growing concern about the potential for an incursion to the UK. Here, Fleur Whitlock, Richard Newton, Simon King, Andra-Maria Ionescu and Sara Higgins provide a timely reminder of key aspects of the virus' biology.
Seroprevalence and Passive Clinical Surveillance of West Nile Virus in Horses from Ecological High-Risk Areas in Western Romania: Exploratory Findings from a Cross-Sectional Study. This cross-sectional study evaluated the seroprevalence and clinical impact of West Nile virus (WNV) infection in horses from three ecologically high-risk counties in western Romania (Timiș, Arad, and Bihor) between 2023 and 2025. A total of 306 unvaccinated horses were tested using a commercial ELISA, with 8.17% testing positive for WNV antibodies, indicating prior exposure. Passive surveillance for clinical signs during mosquito seasons identified 16 horses with acute neurological symptoms, four of which were confirmed as clinical cases based on WNV-specific IgM positivity, suggesting proba...
Cellular Immune Response in Horses After West Nile Neuroinvasive Disease. West Nile virus (WNV) is a mosquito-borne neurotropic virus that causes neurologic disease in both humans and horses. Yet the long-term cellular immune response following natural infection in horses remains poorly understood. This study aims to evaluate the WNV-specific T-cell response in horses recovered from West Nile neuroinvasive disease (WNND). Twelve client-owned horses (4 Hungarian sport horses, 2 Lippizaners, 1 KWPN, 1 Shagya Arabian, 1 Friesian, 1 Gidran, 1 Andalusian, and 1 draft cross horse) with confirmed clinical WNV infection were enrolled, and peripheral blood mononuclear cells ...
Serological differentiation of West Nile, Usutu, and tick-borne encephalitis virus antibodies in birds and horses using mutant E protein ELISAs. West Nile virus (WNV), Usutu virus (USUV) and tick-borne encephalitis virus (TBEV) are worldwide endemic zoonotic orthoflaviviruses, often co-circulating in the same areas. Serological studies in animals, mostly birds and horses, are important means to monitor the spread of these viruses and the infection risks for humans. However, cross-reactive antibodies to these structurally similar flaviviruses frequently impact serological differentiation in enzyme-linked immunosorbent assays (ELISAs), hence time-consuming virus neutralization tests (VNTs) have to be employed in laboratories with high bi...
West Nile virus transmission in the Metropolitan Area of Barcelona (Spain): A One-Health surveillance approach. West Nile virus (WNV), mainly transmitted by mosquitoes, poses significant health risks to humans and horses, particularly in endemic regions. The first detection of WNV lineage 2 in Spain was in 2017 in Catalonia (northeastern Spain). In 2023, WNV was confirmed in a young yellow-legged gull and a probable human case was notified within the urban settings. We aimed to define the zone of WNV circulation in the Barcelona Metropolitan Area where these infections occurred and the effectiveness of the One Health approach for early WNV detection. The Catalan WNV surveillance and control programs in...
West Nile Virus Antibody Prevalence in Horses During the 2023 Outbreak in Tunisia, North Africa. A total of 20 horses belonging to the Pasteur Institute of Tunis used for the production of therapeutic serum antiscorpion venom were tested for the presence of antibodies anti-West Nile virus (WNV) during the 2023 outbreak of West Nile disease that affected humans and horses in Tunisia. Of the 20 samples tested in November 2023 by enzyme-linked immuno-sorbent assay (ELISA), five were positive, leading to a seroprevalence of 25%. Since the number of horses is not substantial, all samples were tested also by virus microneutralization test (MNT) using the Tunisian strain of WNV lineage 1 isolate...
Zoonotic pathogens in equids in Central Europe: a systematic review. Equids serve diverse roles in contemporary society. Their use as companion animals, in sports, transportation, and food production brings them into close contact with humans, creating potential zoonotic risks. This review had two objectives: (i) to catalogue zoonotic pathogens detected in equids across Central Europe, and (ii) to analyse research trends and collaborations in equid zoonosis studies within the region. We conducted a systematic literature search following PRISMA guidelines to identify publications on naturally occurring zoonotic pathogens in equids from nine countries: Austria, t...
Orthoflavivirus nilense surveillance in the State of Piauí, northeastern Brazil. The cycle of the Orthoflavivirus nilense (West Nile virus - WNV) involves birds and mosquitoes, while humans and equids serve as terminal hosts. In 2014, the first human case in Brazil was confirmed in Piauí State. Objective: To investigate the presence of WNV in birds, mosquitoes, and equids in municipalities of Piauí. Methods: Collections were carried out following recommendations from the Ministry of Health of Brazil, in 11 municipalities (all with human cases or bird mortality), where biological samples were collected from birds, mosquitoes, and equids. The Viral RNA extraction was perfo...
First Detection of West Nile Virus (WNV) Lineage 2 in Mosquitoes in the Republic of Kosovo. West Nile virus (WNV, family Flaviviridae) is the most geographically widespread arbovirus affecting humans. It circulates between wild birds and mosquitoes, while humans and horses are dead-end hosts. In recent years, several outbreaks have been reported from European countries, including the Balkan Peninsula. In the Republic of Kosovo, a southern Balkan country, data on WNV are scarce, and neither mosquito monitoring nor WNV surveillance is established. To address this gap, we aimed to assess a first monitoring approach that should set the basis and support future large-scale activities in t...
Long-Term Humoral Immune Response After West Nile Virus Convalescence in Horses in a Geographic Area of Multiple Orthoflavivirus Co-Circulation. In the last three decades, West Nile virus (WNV, Flaviviridae, Orthoflavivirus genus) has become one of the most important encephalitic agents worldwide, causing substantial numbers of cases in humans and horses every year by re-emerging in endemic areas and emerging in new territories. It is considered that after natural WNV infection, humans and birds develop long-term immunoprotection, but data on immunoprotection in horses is scarce. Objective: West Nile virus infection provides long-term humoral immunity in subclinically infected horses. Methods: Client-owned, naturally WNV subclinically ...
Epidemiology and surveillance of West Nile virus in the Mediterranean Basin during 2010-2023: A systematic review. Climate change can cause spatio-temporal shifts in the epidemiology of various vector borne pathogens, especially in vulnerable areas such as the Mediterranean Basin (MB). Among these pathogens, the West Nile virus (WNV) became endemic in the region. This systematic review and meta-analysis study summarizes WNV epidemiology, molecular characteristics, and surveillance in various MB countries, relying on data and scientific articles on WNV published during 2010-2023. The number of published articles varied across the three MB subregions: Southern Europe (n = 153), North Africa (n = 33), and...
First detection of West Nile virus seropositivity in horses in southern Iraq. West Nile virus (WNV) circulates between birds and mosquitoes, with horses and humans as incidental dead-end hosts. Despite documented cases in neighboring countries and human cases in southern Iraq, no previous studies have investigated WNV in Iraqi horses. Unassigned: To determine the seroprevalence of WNV in horses from three southern Iraqi governorates (Thi-Qar, Misan, and Basrah) between March and June 2024. Unassigned: Blood samples were collected from 236 horses regardless of age, sex, or health status. Serum samples were analyzed using commercial competitive enzyme-linked immunosorbent...
Wastewater surveillance as a tool for understanding West Nile virus transmission and distribution in Oklahoma. West Nile Virus (WNV) is the most widespread and frequently reported mosquito-borne disease in the US, with a high risk of outbreaks. Accurate surveillance of WNV is complicated by many mild or asymptomatic infections, resulting in human cases being under-reported and disease distribution and transmission not being well understood. In this study, we investigated how wastewater surveillance can be used for monitoring WNV in Oklahoma. We analyzed samples collected from wastewater treatment facilities in 16 counties during July 1 to September 31, 2023, for the presence of WNV genetic material and...
Seroprevalence of West Nile, Usutu and tick-borne encephalitis viruses in equids from south-western France in 2023. The circulation of West Nile virus (WNV), Usutu virus (USUV), and tick-borne encephalitis virus (TBEV) was investigated in south-western France during the first six months of 2023, following the emergence of WNV in equids in Gironde, a département in south-western France, in 2022. Blood samples were collected from 494 horses located in the Gironde département and divided into three zones: the Confluence zone, the Intermediate zone and the Arcachon Basin. Samples were tested for WNV-, USUV- and TBEV-specific antibodies. An overall seroprevalence of 14% (95% CI [11-18%]) for orthoflavivirus an...
Stochastic modeling of the horse population and vaccination data indicates low annual vaccination coverage for West Nile virus in Canada (2016-2020). Vaccination is the most efficient tool for preventing West Nile virus (WNV) disease in horses. The objectives of this retrospective study were to: i) estimate the provincial and national horse population in Canada; ii) estimate the annual vaccination coverage for WNV in each province; and iii) compare estimates of provincial annual vaccination coverage. Horse population data (2006-2023) and the number of vaccine doses sold in Canada (2016-2020) were obtained by province. Based on these data and expert consultations, the annual number of vaccine doses administered, and provincial horse populati...
Short-term effect of weather variables on West Nile virus infection in Equids in Spain: A space-time stratified case-crossover design. West Nile virus (WNV) is an arthropod-borne virus primarily transmitted by Culex mosquitoes, among birds, but occasionally infecting humans and equids. Understanding environmental factors on the disease occurrence is crucial for planning effective prevention and control strategies. Our study estimates the short-term effects of ambient temperature, relative humidity and precipitation on weekly cases of WNV in equids in Spain, using a space-time stratified case-crossover design. Because WNV transmission occurs sometime after the weather conditions become favorable for the vector, we aimed to est...
West Nile Virus (WNV): One-Health and Eco-Health Global Risks. West Nile virus (WNV) is an important zoonotic pathogen belonging to the Flaviviridae family, which is endemic in some areas and emerging in others. WNV is transmitted by blood-sucking mosquitoes of the genus Culicoides, Aedes, and Anopheles, and the infection can cause different clinical symptoms. The most common and benign illness in humans is West Nile fever (WNF), but a lethal neurological disease (WNND), related to the neuro-invasiveness of WNV lineage 2, represents the highest health risk of WNV infection. The neuro-clinical form is recognized in mammals (land and cetaceans), particularl...
