West Nile Virus In Horses Research Articles

Orthoflavivirus surveillance in the Netherlands: Insights from a serosurvey in horses & dogs and a questionnaire among horse owners.

Zoonotic arboviruses (arthropod-borne) of the Orthoflavivirus genus, such as West Nile virus (WNV), Usutu virus (USUV) and Tick-borne encephalitis virus (TBEV), are emerging in Northwestern Europe and pose a threat to both human and animal health. In the Netherlands, passive symptomatic surveillance (notification of clinical cases) in horses is one of the main pillars for the early detection of WNV. For such passive surveillance to work properly, horse owners and veterinarians need to recognize symptoms and report suspected cases to the authorities. Currently, little is known about the seroprevalence of orthoflaviviruses in domestic animals in the Netherlands. Therefore, this study aims at identifying the seroprevalence of WNV and USUV in horses and dogs in the Netherlands. Additionally, this study seeks to evaluate the knowledge and perceptions of Dutch horse owners towards mosquito-borne viruses. A cross-sectional serosurvey in horses and dogs was conducted between May 2021 and May 2022. Serum samples were screened using an ELISA and doubtful and positive samples were confirmed by Virus Neutralization Tests for WNV, USUV and TBEV. A validated questionnaire, the MosquitoWise survey, was used to assess the knowledge and perceptions of Dutch horse owners towards mosquito-borne viruses between July and October 2022. The serosurvey revealed a low seroprevalence for WNV in horses and no WNV-positive dogs were found. Similarly, a low USUV seroprevalence was found in dogs. The MosquitoWise survey revealed a high knowledge level for horse owners and high awareness of WNV vaccination but a more limited intent to vaccinate. The low seroprevalences of WNV and USUV indicate many dogs and horses remain susceptible, offering opportunities for trend analysis and surveillance. However, despite multiple recent detections of WNV, USUV, and TBEV in humans, the role of dogs and horses in early detection of human cases is debatable. High awareness among horse owners and the absence of detected equine WNV cases highlight this uncertainty. Continued surveillance is crucial for detecting increased virus circulation and protecting both animal and human health.

Distribution of West Nile virus cases in horses reveals different spatiotemporal patterns in eastern and western Canada.

West Nile virus (WNV) became notifiable in horses in 2003 in Canada and has been reported every year since. The objective of this study was to describe the spatiotemporal distribution of WNV in horses between 2003 and 2020 in Canada. The 848 symptomatic and laboratory-confirmed WNV cases in horses reported to the Canadian Food Inspection Agency between 2003 and 2020. Canada was divided into eastern and western regions for analysis. For each case, location and date of notification were captured. Triennial maps were made to describe the spatiotemporal distribution and expansion of reported cases. The association between year and latitude of cases was investigated with simple linear regressions, and space-time clusters were detected with a permutation scan test. Most of the western region showed an extended distribution of WNV cases from 2003 to 2005 and a high recurrence of cases at the census division level. In the eastern region, the expansion of cases was gradual, with new infected census divisions mostly contiguous to previous ones. There was no association between year and latitude of cases. Six spatiotemporal clusters were detected. This study confirmed the endemicity of WNV in parts of both regions with local peaks in risk varying in time. Prevention and control efforts should focus on previously infected areas based on the spatiotemporal regional distribution patterns. Incursions of WNV to new areas should also be anticipated. These findings could also contribute to enhancing monitoring and prevention of WNV infections in an integrated surveillance system.

Global Seroprevalence of West Nile Virus in Horses of Morocco

West Nile Fever (WNF) is a viral emerging mosquito-borne disease causing mortality and morbidity with varying severity (from mild fever to severe neuroinvasive disease) among human and animal populations in many parts of the world. The current study aimed to confirm the virus circulation and assess the disease seroprevalence in horses of Morocco. A sample of 1171 healthy non-vaccinated (against-WNF) horses, taken from 11 (out of 12) regions of the country during July-December 2016, was primarily tested using competitive ELISA assay (cELISA). All cELISA-reactive positive and doubtful sera (n= 269) were further tested by virus neutralization test (VNT). The results of cELISA test revealed an overall WNF seroprevalence in 21.8% (255/1171) of sampled horses. This rate decreased to 18.8% (220/1171) after the confirmation of VNT. The WNF seroprevalence in the current study varied significantly by age, gender, and breed of the tested horses. Indeed, the higher seropositivity rates were found in the oldest (27.7%), female (22.0%), and saddle (32.1%) horses. However, the origin of animals did not show any significant effect on the West Nile virus infection. The obtained results of the present study, therefore, provided serological and epidemiological evidence of the endemicity of the WNV in horse populations of Morocco.

Epidemiology and Clinical Presentation of West Nile Virus Infection in Horses in South Africa, 2016-2017.

Although West Nile virus (WNV) is endemic to South Africa (RSA), it has only become recognized as a significant cause of neurological disease in humans and horses locally in the past 2 decades, as it emerged globally. This article describes the epidemiological and clinical presentation of WNV in horses across RSA during 2016–2017. In total, 54 WNV-positive cases were identified by passive surveillance in horses with febrile and/or neurological signs at the Centre for Viral Zoonoses, University of Pretoria. They were followed up and compared to 120 randomly selected WNV-negative controls with the same case definition and during the same time period. Of the WNV-positive cases, 52% had fever, 92% displayed neurological signs, and 39% experienced mortality. Cases occurred mostly in WNV-unvaccinated horses <5 years old, during late summer and autumn after heavy rain, in the temperate to warm eastern parts of RSA. WNV-positive cases that had only neurological signs without fever were more likely to die. In the multivariable analysis, the odds of WNV infection were associated with season (late summer), higher altitude, more highly purebred animals, younger age, and failure to vaccinate against WNV. Vaccination is currently the most effective prophylactic measure to reduce WNV morbidity and mortality in horses.

Vigilancia epidemiológica al virus del Oeste del Nilo en municipios del Departamento del Meta

Objetivo. Identificar la presencia del virus del Oeste del Nilo en equinos y mosquitos en ocho municipios del departamento del Meta. Materiales y métodos. La investigación contó con el aval del Comité de bioética de la Universidad de los Llanos. Se analizaron mediante pruebas serológicas y moleculares 613 muestras de equinos criollos y de raza cuarto de milla, destinados a actividades deportivas y de trabajo, con un rango de edad de 2 a 15 años, en los transectos: Villavicencio-Restrepo-Cumaral, San Martín-Castilla la Nueva-Granada y Puerto López-Puerto Gaitán, analizados en 62 pool y 213 mosquitos. Los pool de sueros de equinos y mosquitos fueron analizados por ELISA y PCR. Resultados. No se encontraron animales seropositivos mediante la prueba de ELISA y las pruebas moleculares también fueron negativas. Conclusiones. Aunque en este estudio no se evidenció la presencia de anticuerpos IgM por la técnica de Elisa y las pruebas moleculares (RT-PCR) también fueron negativas para circulación viral, en los municipios objeto de estudio, es importante indicar que la detección molecular en sueros, requiere unos niveles de viremia representativos y que el animal se encuentre en la fase aguda de la enfermedad. Aunque es posible que la población equina se mantenga libre de contacto con el virus, se debe mantener la vigilancia epidemiológica frente a este importante patógeno para la salud humana, especialmente por la presentación de brotes de otros virus zoonóticos como la Encefalitis Equina del Este y Encefalitis Equina Venezolana en los departamentos del Meta y Casanare, contiguo a este.

Seroprevalence of West Nile fever virus in horses in the Belgrade epizootiological area

West Nile fever is a vector borne viral disease that can affect humans, horses, birds and sometimes other species of animals. Every year West Nile fever is detected in the human population in Serbia. The disease often occurs in a subclinical form, but most clinically evident cases occur in horses. Therefore, horses are recommended as a sentinel species for monitoring the general incidence of West Nile fever in a specific territory. Our goal was to determine the prevalence of antibodies against West Nile fever virus in horses in the Belgrade epizootiological area. We examined serum samples from 77 horses to determine the seroprevalence of West Nile fever virus in horses throughout the city of Belgrade. Sera were tested by commercial ELISA tests for detection of specific IgG-class antibodies to West Nile fever virus and for the detection of specific IgM-class antibodies to confirm the presence of old and acute (recent) infections in horses. The results confirmed that West Nile fever virus is widespread, detected in 70.1% of the surveyed horse population in Belgrade, and we also detected 5.1% of acute cases had occurred due to horses being infected in 2019. The seroprevalence of West Nile virus in the horse population in the municipality of Belgrade is increasing.

Serosurvey of West Nile virus in horses and detection of West Nile virus antigen in mosquitoes in Kaduna State, Nigeria.

ABSTRACTWest Nile virus (WNV) causes a mosquito-borne zoonotic disease of public health importance. The aim of this study was to determine the state of WNV infection in horses and detect the virus antigen in mosquitoes trapped in stables in Kaduna State Nigeria. The study was carried out in Kaduna State, Nigeria, and 368 horses were screened for the presence of antibodies against WNV using an IgG competitive enzyme-linked immunosorbent assay. Of the 368 samples tested, 331 (89.9%) were positive for WNV antibodies. Mosquitoes from the stables were tested for WNV antigen using a VectorTest kit, and of the 31 pools of adult mosquitoes tested, only 5 (16.1%) pools tested positive for WNV antigen. This finding showed that WNV infection has occurred in horses and that there is evidence of circulation of the virus by mosquitoes in Kaduna State, Nigeria.

West Nile virus in horses during the summer and autumn seasons of 2015 and 2016, Portugal

West Nile fever (WNF) is an emergent disease in Europe, under surveillance in the European Union. Following a 5-year period of apparent silence (autumn 2010 to summer 2015), West Nile virus (WNV) reemerged in the South of Portugal, in July 2015.Here we present data from the onset, geographic location within mainland Portugal, and outcome of clinical cases of WNV infection in horses in 2015 and 2016. During the transmission seasons of 2015 and 2016, twenty-seven horses, most symptomatic (n=20) were found positive to IgM, pr-E immunoglobulins and VNT, leading to the subsequent report to Animal Disease Notification System of the European Commission (ADNS) by the Portuguese National Authority for Animal Health.Outbreaks occurred in the middle summer (August) and early/mid autumn (October/November) of 2015 and 2016, in the southern regions of the country (Alentejo and Algarve).Compared with the previous WNV transmission seasons of 2004 and 2010, a higher number of cases were reported in 2015 and 2016.The results of our study contribute to increase information concerning the geographic areas affected and time period for WNV transmission risk in Portugal.

Differential Diagnosis of Flavivirus Infections in Horses Using Viral Envelope Protein Domain III Antigens in Enzyme-Linked Immunosorbent Assay

In Australia, infection of horses with the West Nile virus (WNV) or Murray Valley encephalitis virus (MVEV) occasionally results in severe neurological disease that cannot be clinically differentiated. Confirmatory serological tests to detect antibody specific for MVEV or WNV in horses are often hampered by cross-reactive antibodies induced to conserved epitopes on the envelope (E) protein. This study utilized bacterially expressed recombinant antigens derived from domain III of the E protein (rE-DIII) of MVEV and WNV, respectively, to determine whether these subunit antigens provided specific diagnostic markers of infection with these two viruses. When a panel of 130 serum samples, from horses with known flavivirus infection status, was tested in enzyme-linked immunosorbent assay (ELISA) using rE-DIII antigens, a differential diagnosis of MVEV or WNV was achieved for most samples. Time-point samples from horses exposed to flavivirus infection during the 2011 outbreak of equine encephalitis in south-eastern Australia also indicated that the rE-DIII antigens were capable of detecting and differentiating MVEV and WNV infection in convalescent sera with similar sensitivity and specificity to virus neutralization tests and blocking ELISAs. Overall, these results indicate that the rE-DIII is a suitable antigen for use in rapid immunoassays for confirming MVEV and WNV infections in horses in the Australian context and warrant further assessment on sensitive, high-throughput serological platforms such as multiplex immune assays.

Epidemiology and spatio-temporal analysis of West Nile virus in horses in Spain between 2010 and 2016.

During the last decade, West Nile virus (WNV) outbreaks have increased sharply in both horses and human in Europe. The aims of this study were to evaluate characteristics and spatio-temporal distribution of WNV outbreaks in horses in Spain between 2010 and 2016 in order to identify the environmental variables most associated with WNV occurrence and to generate high-resolution WNV suitability maps to inform risk-based surveillance strategies in this country. Between August 2010 and November 2016, a total of 403 WNV suspected cases were investigated, of which, 177 (43.9%) were laboratory confirmed. Mean values of morbidity, mortality and case fatality rates were 7.5%, 1.6% and 21.2%, respectively. The most common clinical symptoms were as follows: tiredness/apathy, recumbency, muscular tremor, ataxia, incoordination and hyperaesthesia. The outbreaks confirmed during the last 7years, with detection of WNV RNA lineage 1 in 2010, 2012, 2013, 2015 and 2016, suggest an endemic circulation of the virus in Spain. The spatio-temporal distribution of WNV outbreaks in Spain was not homogeneous, as most of them (92.7%) were concentrated in western part of Andalusia (southern Spain) and significant clusters were detected in this region in two non-consecutive years. These findings were supported by the results of the space-time scan statistics permutation model. A presence-only MaxEnt ecological niche model was used to generate a suitability map for WNV occurrence in Andalusia. The most important predictors selected by the Ecological Niche Modeling were as follows: mean annual temperature (49.5% contribution), presence of Culex pipiens (19.5% contribution), mean annual precipitation (16.1% contribution) and distance to Ramsar wetlands (14.9% contribution). Our results constitute an important step for understanding WNV emergence and spread in Spain and will provide valuable information for the development of more cost-effective surveillance and control programmes and improve the protection of horse and human populations in WNV-endemic areas.

Seroprevalence of West Nile virus in horses in different Moroccan regions.

West Nile virus‐associated disease is one of the most widespread vector‐borne diseases in the world. In Morocco, the first cases were reported in horses in 1996 and the disease re‐emerged in 2003 and in 2010. The objective of this work was to study the epidemiological situation of WNV‐associated infection in Morocco, by quantifying the seroprevalence of anti‐WNV IgM and IgG antibodies in horses in different bioclimatic regions‐zones of Morocco in 2011. During the months of May, June and July 2011, 840 serum samples were collected from horses in four regions characterized by different environmental and climatic features such as altitude, temperature and precipitation. These environmental‐climatic regions are: the Atlantic plateaus of the Gharb and pre‐Rif region, the North Atlasic plains and plateaus region, the Atlas Mountains and pre‐Atlas region and the plains and plateaus of the Oriental region. All samples were tested for the anti‐WNV IgG antibodies by ELISA and positive sera were confirmed by virus neutralization (VN). An anti‐WNV antibody prevalence map was developed. A total of 261 samples (31%) were found positive by both techniques. The prevalence of the infection was higher in the Atlantic plateaus of the Gharb and pre‐Rif region, in the northern part of the country. Available data concerning the previous WNV‐associated disease outbreaks in Morocco and the preliminary results of this serological survey suggest that the Moroccan northwest is the region at highest risk for WNV circulation. In this region, the climate is more humid with higher rainfall than other regions and milder winter temperatures exist. In the same area, the presence of migratory bird settlements may affect the risk of virus introduction and amplification.

First Serological Evidence of West Nile Virus in Horses and Dogs from Corsica Island, France.

West Nile virus (WNV) is widely distributed over the world, including Europe, Africa, and Asia and spread over the past two decades to North and South America. In the south of France, sporadic cases are frequently described and the virus is endemic in Italy with frequent cases and outbreaks. The aim of this study was to identify a possible WNV circulation in Corsica (French island in the Mediterranean Sea) in sheep, horses, and dogs as sentinel animals for the virus surveillance. In 2014, 386 blood samples were collected from 219 sheep, 96 horses, and 71 dogs, in 12 localities in Corsica, in the oriental coast of Corsica. Each sample was systematically tested for WNV immunoglobulin G using an in-house enzyme-linked immunosorbent assay (ELISA) with inactivated WNV as antigen. The result of the ELISA for the WNV antibody test on the sheep sera was all negative, whereas 9 of 96 horses (9.4%) and 6 of 71 dogs (8.4%) presented WNV antibodies. All the positive samples from horses and dogs were confirmed by serum neutralization test. Although no clinical case in humans and horses was reported to date, this report highlights the necessity to improve WNV surveillance in animals and humans, as well as in blood donors in Corsica.

First serological evidence of West Nile virus in horses and dogs from Corsica Island, France

Abstract West Nile virus (WNV) is widely distributed over the world, including Europe, Africa, and Asia and spread over the past two decades to North and South America. In the south of France, sporadic cases are frequently described and the virus is endemic in Italy with frequent cases and outbreaks. The aim of this study was to identify a possible WNV circulation in Corsica (French island in the Mediterranean Sea) in sheep, horses, and dogs as sentinel animals for the virus surveillance. In 2014, 386 blood samples were collected from 219 sheep, 96 horses, and 71 dogs, in 12 localities in Corsica, in the oriental coast of Corsica. Each sample was systematically tested for WNV immunoglobulin G using an in-house enzyme-linked immunosorbent assay (ELISA) with inactivated WNV as antigen. The result of the ELISA for the WNV antibody test on the sheep sera was all negative, whereas 9 of 96 horses (9.4%) and 6 of 71 dogs (8.4%) presented WNV antibodies. All the positive samples from horses and dogs were confirme...

West Nile Virus Serosurveillance in Wild Boars from the East of Romania

West Nile Virus (WNV) is the etiological agent of the WN fever/encephalitis, a re-emerging zoonosis signalled frequently in the last decades in the whole world. The virus can cause severe neurological disease in horses and humans but in many other species specific WNV seroconversion is signalled and may be an useful epidemiological tool. Wild animals can be vectors for many pathogens but the surveillance is limited due to the particularities of those populations. A preliminary serosurvey study was made to evaluate the circulation of WNV in wild boar population from two counties in the south east of Romania. Antibodies against WNV were detected by a competitive ELISA in 43 (63.24% ) of the 68 tested samples (BuzAƒu County 53.33% and GalaA£i County 71.05%).This is the first attempt to assess the seroconversion of WNV in wild boars in Romania and we can assume that the infection is maintained in tested areas in a sylvatic enzootic transmission circle. Our previous studies had revealed the high seroprevalence of WNV in horses and domestic birds from the studied areas. Moreover, WN encephalitis was diagnosed in humans from GalaA£i and BuzAƒu counties. Our results might bring in light the hypothesis of WNV seroconversion in wild boars and pointto further studies. Taking in accountthat WNV is a Flavivirus ofthe Japanese encephalitis virus antigenic complex, there is a great possibility to cross react with other related viruses infecting the wildboar, so more specific tests are needed in order to confirm our preliminary results

Re-emerging West Nile virus in horses from South Eastern France, 2015

Re-emerging West Nile virus in horses from South Eastern France, 2015

Spatial and temporal distribution of West Nile virus in horses in Israel (1997-2013)--from endemic to epidemics.

With the rapid global spread of West Nile virus (WNV) and the endemic state it has acquired in new geographical areas, we hereby bring a thorough serological investigation of WNV in horses in a longstanding endemic region, such as Israel. This study evaluates the environmental and demographic risk factors for WNV infection in horses and suggests possible factors associated with the transition from endemic to epidemic state. West Nile virus seroprevalence in horses in Israel was determined throughout a period of more than a decade, before (1997) and after (2002 and 2013) the massive West Nile fever outbreak in humans and horses in 2000. An increase in seroprevalence was observed, from 39% (113/290) in 1997 to 66.1% (547/827) in 2002 and 85.5% (153/179) in 2013, with persistent significantly higher seroprevalence in horses situated along the Great Rift Valley (GRV) area, the major birds' migration route in Israel. Demographic risk factors included age and breed of the horse. Significantly lower spring precipitation was observed during years with increased human incidence rate that occurred between 1997–2007. Hence, we suggest referring to Israel as two WNV distinct epidemiological regions; an endemic region along the birds' migration route (GRV) and the rest of the country which perhaps suffers from cyclic epidemics. In addition, weather conditions, such as periods of spring drought, might be associated with the transition from endemic state to epidemic state of WNV.

Serologic survey of West Nile virus in horses from Central-West, Northeast and Southeast Brazil

Since the emergence of West Nile virus (WNV) in North America in 1999, there have been several reports of WNV activity in Central and South American countries. To detect WNV in Brazil, we performed a serological survey of horses from different regions of Brazil using recombinant peptides from domain III of WNV. Positive samples were validated with the neutralisation test. Our results showed that of 79 ELISA-positive horses, nine expressed WNV-specific neutralising antibodies. Eight of the infected horses were from the state of Mato Grosso do Sul and one was from the state of Paraíba. Our results provide additional evidence for the emergence of WNV in Brazil and for its circulation in multiple regions of the country.

Serologic survey of West Nile virus in horses from Central-West, Northeast and Southeast Brazil

Since the emergence of West Nile virus (WNV) in North America in 1999, there have been several reports of WNV activity in Central and South American countries. To detect WNV in Brazil, we performed a serological survey of horses from different regions of Brazil using recombinant peptides from domain III of WNV. Positive samples were validated with the neutralisation test. Our results showed that of 79 ELISA-positive horses, nine expressed WNV-specific neutralising antibodies. Eight of the infected horses were from the state of Mato Grosso do Sul and one was from the state of Paraíba. Our results provide additional evidence for the emergence of WNV in Brazil and for its circulation in multiple regions of the country.

Aserological survey on antibodies against West Nile virus in horses of Khuzestan province

BACKGROUND: West Nile virus (WNV) is a vector-borneagent that is maintained within a bird-mosquito cycle. In humansand equids, infection by this agent is usually asymptomatic, orcharacterized by a mild febrile illness. However, fatal meningoencephalitisor encephalitis may occur. OBJECTIVES:The aim ofthis study was to evaluate the prevalence of WNVinfection andcorrelation of this organism with host and environmentaldeterminants in horses in Khuzestan province. METHODS: In2011-2012, serum samples of 155 horses were randomly collectedfrom 7 zones of Khuzestan province and were examined byELISAassay. RESULTS: Seroprevalence of WNVinfection was70.3% (95% CI: 63.1-77.5%). Statistical analysis showed thatage, zone, presence of lake, type of bed, time of sampling, stayingout of the stable after sunset and the method of insect control aresignificantly associated with infection (p 0.05).CONCLUSIONS: The results of the present study confirm that theWNV infection exists in Khuzestan province. Considering thelocal weather conditions and the facility of vector-bornetransmission, the health authorities should take measures toprevent and control the infection.

Serologic survey of West Nile virus in horses from Central-West, Northeast and Southeast Brazil

Since the emergence of West Nile virus (WNV) in North America in 1999, there have been several reports of WNV activity in Central and South American countries. To detect WNV in Brazil, we performed a serological survey of horses from different regions of Brazil using recombinant peptides from domain III of WNV. Positive samples were validated with the neutralisation test. Our results showed that of 79 ELISA-positive horses, nine expressed WNV-specific neutralising antibodies. Eight of the infected horses were from the state of Mato Grosso do Sul and one was from the state of Paraíba. Our results provide additional evidence for the emergence of WNV in Brazil and for its circulation in multiple regions of the country.