Seroprevalence of West Nile, Usutu and Tick borne encephalitis viruses in equids from southwestern France in 2023

doi:10.21203/rs.3.rs-4688411/v1

Download PDF

Research Article

Seroprevalence of West Nile, Usutu and Tick borne encephalitis viruses in equids from southwestern France in 2023

https://doi.org/10.21203/rs.3.rs-4688411/v1

This work is licensed under a CC BY 4.0 License

You are reading this latest preprint version

The circulation of West Nile virus (WNV), Usutu virus (USUV) and Tick-borne encephalitis virus (TBEV) was investigated in southwestern France within the first six months of 2023 following the emergence of WNV in equids in Gironde county in 2022. Blood samples were collected from 494 horses located in Gironde County divided into three zones: the Confluence, the Intermediate zone and the Arcachon basin and tested for WNV, USUV and TBEV specific antibodies. An overall seroprevalence of 14% (95% CI [11%-18%]) for orthoflavivirus antibody was detected in Gironde county. The highest seroprevalence rate for WNV and USUV were detected in the Confluence zone (9%, 95% CI, [6%-13%] and 5%, 95% CI, [3%-8%] respectively). The type of housing (animals kept in pasture only) and the distance to the nearest bird special protection area (SPA) were identified as risk factors for WNV seropositivity. This paper presents the first seroprevalence study investigating WNV, USUV and TBEV infections, conducted in equids located on the Atlantic coast of France and demonstrates an intense circulation of WNV in this region of France as well as equine USUV specific infection.

West Nile virus (WNV) is a reemerging zoonotic mosquito-borne orthoflavivirus (Flaviviridae family) that represents a growing threat to human and animal health. It is one of the main viral agents causing encephalitis in humans and horses in Europe (Harris et al., 2006). It was identified for the first time in Uganda in 1937 (Smithburn et al., 1940), and its circulation is now evident on all five continents [1]. WNV is maintained in an enzootic cycle involving ornithophilic mosquitoes as vectors (Culex spp.) and wild and resident birds as reservoirs and/or amplifying hosts. The virus can infect approximatively one hundred mammalian host species, which are considered epidemiologically dead-end hosts that do not participate in virus spreading [2]. Among them, only humans and horses are known to develop symptoms following WNV infection. WNV infection is predominantly asymptomatic or can cause flu-like syndrome. In 1 to 10% of cases, neurological signs, the most frequent being ataxia, weakness and muscle fasciculations, are encountered. Some horses develop signs of encephalitis, leading to death or euthanasia [3–5]. In addition, human-to-human transmission of WNV, during blood transfusions or organ transplants, has been extensively documented and remains a major concern in the transfusion context [6, 7]. To reduce the risk of non-vector transmission, Europe introduced precautionary measures to control labile products, such as the exclusion of blood donors for 28 days after a visit to a high-risk area (European Directive 2004/33/EC) [7].

As WNV circulation is heterogeneous between Member States and is a compulsory notifiable disease for birds (since 2021), equines and humans (since 2009) to the European Commission [8], each country has implemented an appropriate surveillance and monitoring system to detect WNV cases in Equidae, avifauna and humans.

Over the last decade, Europe has faced significant changes in the distribution of WNV, as well as two other mosquito-borne orthoflaviviruses, Usutu virus (USUV) and tick-borne encephalitis virus (TBEV) most likely caused by global change and increasing global warming. The three viruses actively cocirculate in most European countries. Infection are mainly subclinical, and accurate estimations of infection incidence rates are difficult.

The surveillance of WNV infection relies heavily on neurological syndromic surveillance in humans and horses in most EU countries. Serosurveillance of equines is also commonly employed to detect virus circulation in a territory, and allows estimation of the intensity of circulation in that territory [1, 9–15]. The outdoor lifestyle of equines and their proximity to humans are good indicators of WNV circulation and human exposure.

In France, WNV was detected for the first time in the Camargue region in 1962. Between 2000 and 2021, several WNV outbreaks of varying intensity were reported, all of which were located in the Mediterranean region and Corsica [16–19]. The 2022 transmission season was marked by the emergence of WNV in southwestern France, on the Atlantic coast. In October 2022, three horses of three distinct stables in Gironde County (Fig. 1) exhibited neurological signs, including ataxia, weakness, muscle fasciculations, and encephalitis. Acute WNV infection was confirmed by serological diagnostic methods (ELISA IgM and IgG) carried out by the French National Reference Laboratory for WNV.

To obtain an accurate assessment of orthoflavivirus circulation in Gironde County, the first seroprevalence survey was conducted among equids located near stables where WNV cases in horses were newly reported in 2022 by investigating possible seroconversion to WNV, USUV and TBEV (Fig. 1).

We aimed to provide valuable insights into the intensity of WNV circulation in 2022 in this newly emerging West Nile virus zone and the associated risk factors for infection. We also evaluated the occurrence of USUV and TBEV in horses in this area.

2.1. Geographical zones

The survey was conducted in Gironde County, southwestern France, characterized by its contrasting landscape. The epidemiological parameters of the three defined zones were determined. The first zone, named Confluence, corresponds to the area where WNV-infected horses were reported in 2022 (Fig. 1). The confluence lies at the junction of two rivers, the Garonne and the Dordogne rivers, where large populations of mosquitoes can be expected. The second zone corresponds to the Arcachon basin. The Arcachon basin lies at the heart of the East Atlantic Flyway, one of the eight most important bird migration corridors on the planet. No cases of WNV infection were reported here. These two zones offer a protected habitat for resident and migratory bird species (represented in green in Fig. 1) that use wetlands as a stopover during their long journeys. These avian tranquility zones encourage interactions between local mosquitoes and competent avian hosts which promotes the establishment of the bird-mosquito-bird transmission cycle of WNV and USUV. The third zone covers the area between the Confluence and the Arcachon basin.

2.2. Study design and sample collection

The study was a cross-sectional prospective study. It took place in April and May 2023, prior to the occurence of seasonal orthoflavivirus activity, to reflect the exposure of horses to WNV, USUV and TBEV during the summer 2022. Animals were recruited by the Clinique Equine de Conques (Saint Aubin de Branne, Gironde, France) through social media and client mailing, according to our three different zones. All owners signed a consent form and treating veterinarians were informed of the procedure. This study was approved by the Ethics Committee for Clinical Research (ComERC) of the Veterinary School of Alfort (EnVA) (Agreement number: 2023-06-23).

Serum samples were collected from 494 adult (> 2-year-old) client-owned horses, ponies, and donkeys residing in 39 different stables of the three studied zones: 306 equids from 25 stables in the Confluence zone, 77 equids from 5 stables in the Arcachon zone, and 111 equids from 9 stables in the intermediate zone (Fig. 1). The animals were unvaccinated against WNV and had been living in the sampling area for the past 6 years throughout 2022 without traveling to the Mediterranean region.

The number of equids sampled in a stable depended on the stable size: all horses were sampled in small stables (fewer than 10 animals), 10 horses were sampled in medium stables (between 10 and 15 animals), and 15 horses were sampled in large stables (more than 15 animals). All animals were asymptomatic at the time of sampling. The 3 cases of 2022 were not included in our cohort, although two of the three corresponding stables were included (Fig. 1).

Serum samples were collected from each included animal. Blood samples were collected in vacutainer dry tubes and centrifuged at 5000 rpm for 5 minutes within 24 hours of collection. The serum was separated, stored at 4°C, and sent to the French National Reference Laboratory for West Nile virus, ANSES (Maisons-Alfort, France) for further analysis.

In addition to sample collection, each stable manager/owner completed a survey consisting in a personal face-to-face interviews to gather information on individual characteristics and stable management. This information included age, sex, hair colour, and type of housing. We also collected information about the environment, such as the distance to the nearest water surface, and the distance to the nearest special protection areas. SPAs have been created for the protection of wild bird species listed in the Annex 1 of the EU bird directive (Directive 79/409/EEC), or that serve as breeding, moulting, wintering, or staging areas for migrating birds. Five SPAs have been defined in the study area around wetlands (Fig. 1).

2.3. Serological testing

ELISA tests

Serum samples were, first, tested for IgG flaviviruses using the commercial Pan-Flavivirus ELISA “ID Screen Flavivirus competition” (Innovative Diagnostic, Montpellier, France). The protocol was performed according to the manufacturer's instructions. The results are expressed as %S/N. If a sample had a %S/N less than or equal to 40%, the sample was considered positive. If it is strictly greater than 50%, the sample is negative. If the result is between 40% and 50%, the sample is considered doubtful. Positive and doubtful results were confirmed for the presence of WNV, USUV and TBEV specific neutralizing antibodies using specific virus neutralization tests.

Virus-neutralization test (VNT)

To identify specifically against which flaviviruses the IgG antibodies detected by ELISA are directed, a virus neutralization test (VNT) was carried out for the three main flaviviruses circulating in France: WNV, USUV and TBEV. This test was performed in 96-well plates as described in Beck et al.[18] .

Briefly, the sera were diluted in a cascade by a factor of 2, from 1:5 to 1:160, in a final volume of 100µL. Fifty microliters of virus was added at an infectious dose of 100 TCID50. After 1h30 of incubation at 37°C and 5% CO₂, 100µL of Vero cells was added at a concentration of 2.10⁵ cells/mL. The neutralizing antibody titer was obtained by observing the cytopathic effect (CPE) under a light microscope after 3-, 4- and 5-days of incubation at 37°C and 5% CO₂ for WNV, USUV and TBEV respectively. The last dilution of serum showing no CPE or a proportion of CPE less than a quarter of the well observed, was noted as the dilution of serum considered where there is still protection against the virus. The neutralizing antibody titer was therefore the inverse of the serum dilution.

Sera neutralizing more than one virus were considered positive for the virus neutralized at a fourfold higher dilution than all other viruses. If a fourfold difference in neutralizing antibody titers was not reached, the serum was considered undifferentiated between the viruses. Sera that tested positive by competitive ELISA and negative by VNT were considered negative.

Statistical analysis

All collected variables were described in terms of frequency distribution (qualitative data) or median and range (quantitative data) classified by the serological status.

Data were analysed using mixed effects logistic regression models, using the stable as a random effect. The dependent variable was the serological status of the animals, according to the seroneutralization test. Fixed effects were animal age (years), sex (male or female), hair colour (light or dark), the type of housing (always on pasture, or both on pasture and indoors), the distance in kilometres (km) to the nearest water surface (intermittent or permanent, of any type: river, canal, estuary, lake, marsh, reservoir etc.), and the distance in km to the nearest special protection area (SPAs).

The exponentiated regression coefficients produced odds ratio (OR) as a measure of the effect of the variables. Starting from the model with all the fixed effects, we selected the most parsimonious model using backward model selection based on the likelihood ratio test, p-value < 0.05.

We used the nonparametric approach proposed by Vaumourin et al. (2014) to test whether the association between positive VNT results against WNV, USUV and TBEV (i.e. the number of equids positive for 1, 2 or 3 of these viruses) significantly differed from the expected distribution under the null hypothesis of independent positive results.

All the statistical analyses were performed using R 4.3.3 (R Core Team 2024). Mixed effects logistic regression models were fitted using the lme4 package [20]. Model selection was performed using the buildmer package [21].

This study included 494 adults: 334 horses, 151 ponies and 9 donkeys of which 271 were male and 223 were female. The majority (412 horses) were active at the time of sampling: 328 animals lived in pasture, whereas 166 had a mixed lifestyle (stable and pasture). Regarding hair coat color, 331 animals had a dark coat, while 163 had a light coat.

3.1 ELISA and VNT

Of the 494 horses included in the study, 70 were positive for orthoflavivirus antibodies by competitive ELISA yielding a seroprevalence rate of 14% (95% CI [11%-18%]). Among them, 60 animals were located in 20 stables in the Confluence zone, 5 horses were housed in 4 stables in the Intermediate zone and 1 was based on 1 stall in the Arcachon area (Table 1).

Table 1

Comparative serological results among selected horses in the Confluence, Intermediate and Arcachon zones in Gironde county
		Geographical zone
		Confluence	Intermediate	Arcachon
Tested horses/stables		306/25	111/9	77/5
ELISA results: Positive horses/stables Animal prevalence (95% CI)		64/20 0.21 (0.16–0.26)	5/4 0.05 (0.02–0.10)	1/1 0.01 (0.00-0.07)
VNT results in ELISA-positive animals: Positive horses/stables Animal prevalence (95% CI)	WNV USUV TBEV WNV USUV TBEV	27/13 14/5 6/4 0.09 (0.06–0.13) 0.05 (0.03–0.08) 0.02 (0.01–0.04)	3/2 1/1 1/1 0.03 (0.01–0.08) 0.01 (0.0-0.05) 0.01 (0.0-0.05)	1/1 0/0 0/0 0.01 (0.0-0.07) 0.0 (0.0-0.05) 0.0 (0.0-0.05)

Within the Confluence zone, 27 equids from 13 different stables were positive for WNV by VNT (9%, 95% CI, [6%-13%]). Within the same zone, 14 equids from 5 different stables were positive for USUV (5%, 95% CI, [3%-8%]), and 6 equids from 4 different stables were positive for TBEV (2%, 95% CI, [1%-4%]). In the intermediate zone, 3 equids housed on 2 stables were positive for WNV (3%, 95% CI, [1%-8%]), one horse was positive for TBEV and another horse was positive for USUV neutralising antibodies (1%, 95% CI, [0%-5%]). For the Arcachon zone, only one horse was positive for WNV (1%, 95% CI, [0%-7%]), and no horse was seropositive for the other viruses (Table 1 and Fig. 2).

Undifferentiable VNT results were also observed. In total, 24 equids tested positive for WNV, 5 horses tested positive for both WNV and USUV, 2 horses tested positive for WNV and TBEV, and none tested positive for all three viruses simultaneously (WNV, USUV, TBEV). Additionally, 9 horses tested positive for USUV only, 1 horse tested positive for both USUV and TBEV, and 4 horses tested positive for TBEV only (Table 2).

Table 2

Association between VNT serological status for WNV, USUV and TBEV
WNV	USUV	TBEV	Number of animals
Positive	Positive	Positive	0
Positive	Positive	Negative	5
Positive	Negative	Positive	2
Positive	Negative	Negative	24
Negative	Positive	Positive	1
Negative	Positive	Negative	9
Negative	Negative	Positive	4
Negative	Negative	Negative	449
Total			494

The individual characteristics of the sampled animals as a function of their WNV and USUV serostatus are shown in Table 3. The qualitative comparison showed that horses tested positive for WNV were mainly male kept on pasture only. This does not apply to horses seropositive for the Usutu virus.

Table 3

Characteristics of horses as a function of the WNV and USUV serostatus.
Individual horse characteristics	WNV n (proportion) or median (range)		USUV n (proportion) or median (range)
	Positive horses	Negative horses	Positive horses	Negative horses
Sex .Male .Female	19 (0.70) 8 (0.30)	162 (0.58) 117 (0.42)	8 (0.57) 6 (0.43)	173 (0.59) 119 (0.41)
Age	13 (2–30)	11 (2–35)	10.5 (6–25)	11 (2–35)
Hair color .Dark .Light	14 (0.52) 13 (0.48)	197 (0.29) 82 (0.71)	9 (0.64) 5 (0.36)	202 (0.69) 90 (0.31)
Type of housing .Pasture only .Mixed pasture/stable	23 (0.85) 4 (0.15)	158 (0.57) 121 (0.43)	9 (0.64) 5 (0.36)	172 (0.59) 120 (0.41)

3.2 Risk factor analysis

A mixed effects logistic regression model of VNT serostatus was fitted for WNV and USUV only, since for TBEV, the number of seropositive stables and equids was very low. Furthermore, we focused our analysis on the Confluence zone, where the vast majority of WNV and USUV seropositive equids were located (Table 3). For WNV, model selection allowed us to identify two risk factors of VNT seropositivity: the type of housing with a strongly increased risk in animals always kept on pasture (odds-ratio [OR] = 4.99) and the distance to the nearest SPA, with a decreasing risk when this distance increased ([OR] = 0.85 for a 1km increase) (Table 4). Other variables (age, sex, hair colour and distance to the nearest water surface) were not retained in the selected model. For USUV, model selection resulted in an empty model (containing the intercept only) and did not allow the identification of any seropositivity risk factors.

Table 4

Mixed effects logistic regression model of the VNT WNV serological status of the horses sampled in the Confluence zone
Variable	Value	Odds-ratio (95% CI)
Intercept		0.10 (0.03–0.27)
Type of housing	Pasture and indoors	Reference
	Pasture only	4.99 (1.83–17.47)
Distance to the nearest SPA	Increase by 1km	0.85 (0.78–0.93)

Finally, we detected a significant association between WNV and USUV serological status (p = 0.006), with the number or number of equids positive for both viruses (5 animals) being significantly higher than the expected 95% interval under the null hypothesis (0–4 animals).

Over the last decade, France has witnessed a changing epidemiology of WNV, USUV and TBEV orthoflaviviruses with increased incidence of diseases in vertebrate hosts [1, 14, 22].

From cohorts of equines located in the three defined areas of Gironde County, we demonstrated WNV seroprevalence rates ranging from 9% (95% CI [6–13]) in the Confluence area to 3% (95% CI [1–8]) in the intermediate area and 1% (95% CI[0–7]) in the Arcachon basin. These findings are comparable to previous reports from Kosovo [23], Spain [24–27] Germany [28–31] and France [16, 17]. In the Camargue region, which has been considered as the historical area of WNV circulation in France since the 1960s, the seroprevalence rate among equines estimated between 2016 and 2020 is slightly higher at approximatively 13% [17].

As for WNV, the highest USUV seroprevalence rate observed in horses was obtained in the Confluence area (5%). It was null near the Arcachon basin.

Therefore, the Confluence area appears to be a hot spot for Culex-borne orthoflavivirus circulation. Our data showed a low percentage of seropositive individuals infected with TBEV (0,3%). Nevertheless, this low seroprevalence rate does not allow us to conclude that TBEV is circulating in southwestern France. The virus is known to circulate in the northeastern part of the country[32–34], with outbreaks detected further south in Jura and other regions [35]. Further investigations in ticks and reservoir animals such as rodents are needed to confirm the presence of TBEV in the Nouvelle Aquitaine region.

In this study, we analysed the risk factors that might affect the susceptibility of horses to WNV infection. The risk of exposure to WNV increased when horses were kept outdoors, and thus were more exposed to vector bites, and when the stable was close to protected areas to preserve the avian biodiversity they harbor (SPAs). In and around these areas, bird and vector species assembly may favor local WNV circulation, as already suggested in southeastern France. This finding is in line with the association, at the European level, between West-Nile disease occurrence in humans and the local diversity of wild bird species [36] [37] .

Age, sex, horse color and distance to the nearest water surface were not identified as risk factors associated with WNV and USUV seropositivity. Our data are consistent with those of García-Bocanegra et al [38]; Vanhomwegen et al [39] who showed no significant differences among age classes; of Durand et al [16] in France, Hassine et al in Jordania [40] and Bażanów et al in horses in Poland [41] who reported the absence of an effect of gender on WNV and USUV seropositivity. Analyses of the color of horse coats are rare in WNV seroprevalence studies in horses. The results from several research groups are disparate, with studies showing an association between darker color and a lower WNV seroprevalence rate [42, 43] and others demonstrating no correlation between this variable and WNV and USUV seropositivity [44].

Interestingly, we did not find a correlation between the seroprevalence of mosquito-borne viruses and the nuisance caused by mosquitoes evaluated by owners. As it is a personal assessment and may vary from one individual to another, our data here do not allow conclusions to be drawn.

The emergence of WNV in this new region of France raised several questions, particularly regarding the factors that favored its introduction into this area. Our main hypothesis is that the introduction of WNV into Nouvelle Aquitaine region occurred through migratory birds. Indeed, the region is located on a migratory corridor of different migratory bird species such as the grey crane, the red kite, the graylag goose and passerines. In addition, the large fire of July 2022, which burned more than 30,000 hectares of forest in Gironde (particularly in La Teste de Buch, Landiras, Landiras St Magne, Saumos and Arès) [45], may lead to the disruption of ecosystems and play a role in the new distribution of WNV. Forest fires can disrupt ecosystems and displace wildlife, potentially leading to increased interactions between humans and infected animals/mosquitoes [46]. Investigations are needed to identify the resident and amplifying avian species that may be involved in the endemicity of WNV in this region of France. The number of equine and avian cases recorded by the French National Reference Laboratory for West Nile during the 2023 transmission season suggests that the virus tends to establish itself and extend its range. Cases have been detected in departments bordering the Gironde especially in Charentes Maritime and Charente.

Carrying out seroprevalence surveys such as the one conducted in this study is essential for strengthening monitoring of WNV circulation. This helps us to understand viral emergence and evaluate the intensity of circulation in new areas. The seroprevalence survey carried out close to syndromic cases diagnosed in 2022 identified areas with high viral circulation. In 2023, these data enabled mosquito traps to be set in mid-July, providing rapid evidence of active circulation of the West Nile and Usutu viruses in the Confluence area. These data have played a major part in the rapid implementation of the measures needed to ensure the safety of products derived from the human body (blood and organ donations) throughout the Gironde and Charente Maritime, a neighbouring department [47]. Horse owners located in the Confluence zone were encouraged to vaccinate their animals to prevent WNV infection in 2024 and the development of severe forms of the disease.

This first seroprevalence study conducted in equids located in Gironde County on the Atlantic coast of France showed that WNV, USUV and an orthoflavivirus belonging to the TBEV serocomplex circulate in this area and infect horses in 2022. Horses, known as sentinel of WNV infection, exhibited intense circulation of this virus in this region of France as well as equine USUV specific infection. This study confirmed the usefulness of serosurveys in horses for detecting the circulation of orthoflaviviruses, especially WNV, in specific regions.

CPE CytoPathic Effect

ELISA Enzyme-liked immunabsorbent assay

IgG Immunoglobulin G

IgM Immunoglobulin M

OR Odd Ratio

SPA Special Protection Area

TBEV Tick-Borne Encephalitis Virus

TCID50 Tissue Culture Infectious Dose 50

USUV Usutu Virus

VNT Virus Neutralisation Test

WNV West Nile Virus

This study was approved by the Ethics Committee for Clinical Research (ComERC) of the Veterinary School of Alfort (EnVA) (Agreement number: 2023-06-23).

Acknowledgements

We would like to thank equine owners for taking part in the serological survey. This research was conducted in part under the French and European laboratory for West Nile Virus.

Author contributions

G.G., A.L., T.T., conceptualized the project.; C.V.M., G.G., N.C., C.M.P., E.Q., B.D., and C.L. contributed to the methodology; N.C., C.B., M.D., M.DM., collected the sera; C.V.M, M.D., T.H., M.C., did the laboratory tests; G.G., C.V.M, B.D., C.L. and N.C., analysed the data; , N.C, C.V.M., G.G., wrote the original draft; C.V.M, N.C., B.D., and G.G. reviewed and edited the original draft; G.G., M.D. and C.V.M., supervised the study; G.G., and C.V.M. contributed to the funding acquisition. All authors reviewed and approved the final draft.

Fundings

We acknowledge the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) and the National Reference Laboratory for West Nile Virus for funding the research activities.

Data availability

The datasets of the current study are available from the corresponding author upon reasonable request.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

Footnotes

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Contributor Information

Camille V. Migné, Email: [email protected]

Gaëlle Gonzalez, Email: [email protected]

Simonin Y (2024) Circulation of West Nile Virus and Usutu Virus in Europe: Overview and Challenges. Viruses, 16(4)
Root J (2013) West Nile virus associations in wild mammals: a synthesis. Arch Virol 158(4):735–752
Lecollinet S et al (2019) Viral Equine Encephalitis, a Growing Threat to the Horse Population in Europe? Viruses, 12(1)
Angenvoort J et al (2013) West Nile viral infection of equids. Vet Microbiol 167(1–2):168–180
Cavalleri JV et al (2022) European College of Equine Internal Medicine consensus statement on equine flaviviridae infections in Europe. J Vet Intern Med 36(6):1858–1871
Iwamoto M et al (2003) Transmission of West Nile virus from an organ donor to four transplant recipients. N Engl J Med 348(22):2196–2203
Pisani G et al (2016) West Nile Virus in Europe and Safety of Blood Transfusion. Transfus Med Hemother 43(3):158–167
Européenne LC (2018) RÈGLEMENT D'EXÉCUTION (UE) 2018/1882 DE LA COMMISSION. Journal officiel de l'Union européenne
Assaid N et al (2020) Evidence of circulation of West Nile virus in Culex pipiens mosquitoes and horses in Morocco. Acta Trop 205:105414
Benjelloun A et al (2017) Seroprevalence of West Nile virus in horses in different Moroccan regions. Vet Med Sci 3(4):198–207
Ben-Mostafa KK et al (2023) Evidence of West Nile Virus Circulation in Horses and Dogs in Libya. Pathogens, 13(1)
Braks MAH, Duijster JW, Stroo CAJ (2022) [West Nile virus unexpectedly in the Netherlands]. Ned Tijdschr Geneeskd, p 166
Cadar D, Simonin Y (2022) Human Usutu Virus Infections in Europe: A New Risk on Horizon? Viruses, 15(1)
Van Heuverswyn J et al (2023) Spatiotemporal spread of tick-borne encephalitis in the EU/EEA, 2012 to 2020. Euro Surveill, 28(11)
Ziegler U et al (2019) West Nile virus epizootic in Germany, 2018. Antiviral Res 162:39–43
Durand B et al (2002) West Nile virus outbreak in horses, southern France, 2000: results of a serosurvey. Emerg Infect Dis 8(8):777–782
Constant O et al (2022) One Health surveillance of West Nile and Usutu viruses: a repeated cross-sectional study exploring seroprevalence and endemicity in Southern France, 2016 to 2020. Euro Surveill, 27(25)
Beck C et al (2020) Contrasted Epidemiological Patterns of West Nile Virus Lineages 1 and 2 Infections in France from 2015 to 2019. Pathogens, 9(11)
Constant O et al (2020) Evidence of Exposure to USUV and WNV in Zoo Animals in France. Pathogens, 9(12)
Bates D et al (2015) Fitting Linear Mixed-Effects Models Using lme4. J Stat Softw 67(1):1–48
Voeten CC (2023) buildmer: Stepwise Elimination and Term Reordering for Mixed-Effects Regression
Čabanová V et al (2023) Co-Circulation of West Nile, Usutu, and Tick-Borne Encephalitis Viruses in the Same Area: A Great Challenge for Diagnostic and Blood and Organ Safety. Viruses, 15(2)
Rexhepi A et al (2021) First Serological Evidence of West Nile Virus Among Equines and Birds in Kosovo, 2018–2019. Vector Borne Zoonotic Dis 21(2):116–120
Magallanes S et al (2023) Long-term serological surveillance for West Nile and Usutu virus in horses in south-West Spain. One Health 17:100578
Napp S et al (2021) Widespread Circulation of Flaviviruses in Horses and Birds in Northeastern Spain (Catalonia) between 2010 and 2019. Viruses, 13(12)
Jiménez-Clavero MA et al (2010) West Nile virus serosurveillance in horses in Donana, Spain, 2005 to 2008. Vet Rec 167(10):379–380
García-Carrasco JM et al (2023) West Nile virus in the Iberian Peninsula: using equine cases to identify high-risk areas for humans. Euro Surveill, 28(40)
Gothe LMR et al (2023) Horses as Sentinels for the Circulation of Flaviviruses in Eastern-Central Germany. Viruses, 15(5)
Bergmann F et al (2022) Seroepidemiological Survey of West Nile Virus Infections in Horses from Berlin/Brandenburg and North Rhine-Westphalia, Germany. Viruses, 14(2)
Bestehorn M et al (2018) Phylogenetics of tick-borne encephalitis virus in endemic foci in the upper Rhine region in France and Germany. PLoS ONE 13(10):e0204790
Ganzenberg S et al (2022) Seroprevalence and Risk Factors for Equine West Nile Virus Infections in Eastern Germany, 2020. Viruses, 14(6)
Bournez L et al (2020) Disappearance of TBEV Circulation among Rodents in a Natural Focus in Alsace, Eastern France. Pathogens, 9(11)
Gonzalez G et al (2022) A One-Health Approach to Investigating an Outbreak of Alimentary Tick-Borne Encephalitis in a Non-endemic Area in France (Ain, Eastern France): A Longitudinal Serological Study in Livestock, Detection in Ticks, and the First Tick-Borne Encephalitis Virus Isolation and Molecular Characterisation. Front Microbiol 13:863725
Parfut A et al (2023) Tick-borne encephalitis in pediatrics: An often overlooked diagnosis. Infect Dis Now 53(2):104645
Bournez L et al (2019) Exposure of Wild Ungulates to the Usutu and Tick-Borne Encephalitis Viruses in France in 2009–2014: Evidence of Undetected Flavivirus Circulation a Decade Ago. Viruses, 12(1)
Durand B et al (2005) Serosurvey for West Nile virus in horses in southern France. Vet Rec 157(22):711–713
Durand B et al (2017) Geographic variations of the bird-borne structural risk of West Nile virus circulation in Europe. PLoS ONE 12(10):e0185962
García-Bocanegra I et al (2012) Monitoring of the West Nile virus epidemic in Spain between 2010 and 2011. Transbound Emerg Dis 59(5):448–455
Vanhomwegen J et al (2017) Circulation of Zoonotic Arboviruses in Equine Populations of Mallorca Island (Spain). Vector Borne Zoonotic Dis 17(5):340–346
Ben Hassine T et al (2014) First detection of co-circulation of West Nile and Usutu viruses in equids in the south-west of Tunisia. Transbound Emerg Dis 61(5):385–389
Bażanów B et al (2018) A Survey on West Nile and Usutu Viruses in Horses and Birds in Poland. Viruses, 10(2)
Aharonson-Raz K et al (2014) Spatial and temporal distribution of West Nile virus in horses in Israel (1997–2013)--from endemic to epidemics. PLoS ONE 9(11):e113149
Azmi K et al (2017) West Nile Virus: Seroprevalence in Animals in Palestine and Israel. Vector Borne Zoonotic Dis 17(8):558–566
Guerrero-Carvajal F et al (2021) Serological evidence of co-circulation of West Nile and Usutu viruses in equids from western Spain. Transbound Emerg Dis 68(3):1432–1444
BUCCIO F (2022) INCENDIES ÉTÉ 2022 Gironde et Landes Retour d’expérience
Moritz MA, Batllori E, Bolker BM (2023) The role of fire in terrestrial vertebrate richness patterns. Ecol Lett 26(4):563–574
publique HC (2022) .d.l.s., Avis sur la sécurisation des produits du corps humain dans un contexte de circul We would like to thank equine owners for taking part in the serological survey. ation du virus West Nile en France métropolitaine

Download PDF

Reviewers agreed at journal
17 Jul, 2024
Reviewers invited by journal
12 Jul, 2024
Editor invited by journal
05 Jul, 2024
Editor assigned by journal
05 Jul, 2024
First submitted to journal
05 Jul, 2024

You are reading this latest preprint version

Seroprevalence of West Nile, Usutu and Tick borne encephalitis viruses in equids from southwestern France in 2023

Status:

Version 1

Abstract

Figures

Introduction

Material and methods

2.1. Geographical zones

2.2. Study design and sample collection

2.3. Serological testing

ELISA tests

Virus-neutralization test (VNT)

Statistical analysis

Results

3.1 ELISA and VNT

3.2 Risk factor analysis

Discussion

Conclusion

Abbreviations

Declarations

References

Status:

Version 1