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

West Nile Virus: An Update Focusing on Southern Europe

West Nile Virus (WNV) is a zoonotic, vector-borne pathogen affecting humans and animals, particularly in Europe. The virus is primarily transmitted through mosquitoes that infect birds, which serve as the main reservoirs. Humans and horses are incidental hosts. This review focuses on the epidemiology of WNV in southern Europe, particularly its increasing prevalence. Methods included an extensive literature review and analysis of recent outbreaks. WNV is largely asymptomatic in humans, but a small percentage can develop West Nile neuroinvasive disease (WNND), leading to severe neurological symptoms and fatalities. Horses can also suffer from neurological complications, with high mortality rates. Climate change, migratory birds, and mosquito population dynamics contribute to the virus spread across Europe. Control efforts focus on vector management, and while vaccines are available for horses, none has been approved for humans. Surveillance, particularly of bird and mosquito populations, and further research into the virus molecular structure are crucial for understanding and mitigating future outbreaks.

The key role of Spain in the traffic of West Nile virus lineage 1 strains between Europe and Africa

BACKGROUND

West Nile Virus (WNV) is a zoonotic arbovirus worldwide spread. Seasonal WNV outbreaks occur in the Mediterranean basin since the late 1990's with ever-increasing incidence. In Southern Spain WNV is endemic, as disease foci - caused by WNV lineage 1 (WNV-L1) strains - occur every year. On the contrary, WNV-L2 is the dominant lineage in Europe, so most European WNV sequences available belong to this lineage, WNV-L1 sequences being still scarce.

METHODS

To fill this gap, this study reports the genetic characterisation of 27 newly described WNV-L1 strains, involved in outbreaks affecting wild birds and horses during the last decade in South-Western Spain.

RESULTS

All strains except one belong to the Western Mediterranean-1 sub-cluster (WMed-1), related phylogenetically to Italian, French, Portuguese, Moroccan and, remarkably, Senegalese strains. This sub-cluster persisted, spread and evolved into three distinguishable WMed-1 phylogenetic groups that co-circulated, notably, in the same province (Cádiz). They displayed different behaviours: from long-term persistence and rapid spread to neighbouring regions within Spain, to long-distance spread to different countries, including transcontinental spread to Africa. Among the different introductions of WNV in Spain revealed in this study, some of them succeeded to get established, some extinguished from the territory shortly afterwards. Furthermore, Spain's southernmost province, Cádiz, constitutes a hotspot for virus incursion.

CONCLUSION

Southern Spain seems a likely scenario for emergence of exotic pathogens of African origin. Therefore, circulation of diverse WNV-L1 variants in Spain prompts for an extensive surveillance under a One Health approach.

Factors affecting populations of the endemic Iberian hare (Lepus granatensis) after the first myxomatosis outbreaks in Central Spain

The Iberian hare (Lepus granatensis) is an endemic species distributed in Spain and Portugal. Myxomatosis outbreaks affecting this species were detected in 2018 in Central and Southern Spain, spreading afterward. Aiming to evaluate factors affecting the status of hare population after the arrival of myxomatosis, we conducted 108 nocturnal hare counts in Central Spain during two study periods (winter/spring and summer/autumn) in 54 different hunting grounds, covering 1071 km and observing 884 individuals. The mean density in winter/spring was 7.66 hares/100 ha, (range 6.14-9.54/100 ha), while in summer/autumn, it was 3.4 hares/100 ha (range 2.6-4.4/100 ha). Densities of hares were not affected by the dominant habitat and the presence/absence of myxomatosis outbreaks. Hares were more abundant at hunting grounds at a higher altitude and in those conducting targeted management, while detection of myxomatosis was related to lower altitude and higher levels of game management. A MaxEnt model used to generate a risk map for myxomatosis occurrence showed that the temperature annual range was the most important predictor, which suggests that environmental factors affecting myxomatosis vectors (mosquitoes, fleas, and ticks) could play a key role in disease transmission. As myxomatosis in hares is becoming endemic, hare densities may be improved by game management and the monitoring and surveillance of this emerging disease. These surveillance programs could be the basis of effective collaborations between hunters, researchers, and environmental managers.

West Nile virus in the Iberian Peninsula: using equine cases to identify high-risk areas for humans

BackgroundWest Nile virus (WNV) is a flavivirus with an enzootic cycle between birds and mosquitoes; humans and horses are incidental dead-end hosts. In 2020, the largest outbreak of West Nile virus infection in the Iberian Peninsula occurred, with 141 clusters in horses and 77 human cases.AimWe analysed which drivers influence spillover from the cycle to humans and equines and identified areas at risk for WNV transmission.MethodsBased on data on WNV cases in horses and humans in 2020 in Portugal and Spain, we developed logistic regression models using environmental and anthropic variables to highlight risk areas. Models were adapted to a high-resolution risk map.ResultsCases of WNV in horses could be used as indicators of viral activity and thus predict cases in humans. The risk map of horses was able to define high-risk areas for previous cases in humans and equines in Portugal and Spain, as well as predict human and horse cases in the transmission seasons of 2021 and 2022. We found that the spatial patterns of the favourable areas for outbreaks correspond to the main hydrographic basins of the Iberian Peninsula, jointly affecting Portugal and Spain.ConclusionA risk map highlighting the risk areas for potential future cases could be cost-effective as a means of promoting preventive measures to decrease incidence of WNV infection in Europe, based on a One Health surveillance approach.

Detection of West Nile and Usutu Virus RNA in Autumn Season in Wild Avian Hosts in Northern Italy

West Nile (WNV) and Usutu (USUV) viruses are two mosquito-borne viruses belonging to the family Flaviviridae and genus Flavivirus. The natural transmission cycle of WNV and USUV involves mosquitoes and birds, while mammals are thought to be accidental hosts. The goal of this study was to report-in the context of "off-season monitoring" and passive surveillance-the detection of WNV and USUV RNA in wild birds. To this end, we analyzed biological samples of wild birds in Northern Italy, from October to May, hence outside of the regional monitoring period (June-September). The virological investigations for the detection of USUV and WNV RNA were performed using real-time PCR on frozen samples of the brain, myocardium, kidney, and spleen. In a total sample of 164 wild birds belonging to 27 different species, sequences of both viruses were detected: four birds (2.44%) were positive for WNV and five (3.05%) for USUV. Off-season infections of WNV and especially USUV are still widely discussed and only a few studies have been published to date. To the best of our knowledge, this study is the first report on the detection of USUV RNA until December 22nd. Although further studies are required, our results confirm the viral circulation out-of-season of Flavivirus in wild birds, suggesting reconsidering the epidemiological monitoring period based on each individual climate zone and taking into consideration global warming which will play an important role in the epidemiology of vector-borne diseases.

Monitoring the epidemic of West Nile virus in equids in Spain, 2020-2021

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 clinically affected horses using real time RT-PCR. Molecular analysis evidenced high nucleotide identity with WNV sequences obtained from humans, birds and mosquitoes from Spain and Italy between 2020 and 2022. Between five and eight months after the WNV epidemic, a total of 724 equids (including 485 unvaccinated and 239 vaccinated animals) from 113 of the 125 affected herds in Andalusia were sampled. IgM and IgG antibodies against WNV were detected in 1.6% (8/485; 95%IC: 0.0-2.5) and 61.9% (300/485; 95%IC: 58.3-65.5) of the unvaccinated individuals, respectively. The seropositivity in vaccinated horses was 86.6% (207/239). The main risk factors associated with WNV exposure in unvaccinated equids were the breed (crossbreed), the location of animals in spring-summer (outside), and the presence of natural water ponds close to the surveyed herds. The high individual seroprevalence obtained in the affected herds indicates that WNV circulation was more widespread than the reported by passive surveillance during the WNV epidemic in 2020. The re-emergence of WNV in 2020 in southern Spain evidenced the needed to improve integrated surveillance systems, minimizing the impact of future cases in equids and humans in high-risk areas.

West-Nil-Virus-Infektion bei 12 Pferden in Mitteldeutschland

Gegenstand und Ziel Die Vorstellungsgründe, klinische Symptomatik, Diagnostik, Therapie und Ergebnis der Therapie von 12 Pferden mit klinisch apparenter West-Nil-Virus (WNV)-Infektion werden beschrieben.

Material und Methoden Fallserie

Ergebnisse Die adulten Pferde (Alter 6–18 Jahre, 7 Stuten, 5 Wallache) aus Sachsen oder Sachsen-Anhalt wurden zwischen September 2018 und September 2020 mit unterschiedlichen Vorberichten vorgestellt. Alle Pferde wurden im August oder September vorgestellt und keines der Pferde war gegen das WNV geimpft. Fieber war das häufigste Allgemeinsymptom und trat bei 8/12 Pferden auf. An neurologischen Symptomen traten Muskelfaszikulationen (11/12 Pferde), Ataxie (8/12 Pferde) sowie Hyperästhesie und Kopfschiefhaltung (je 6/12 Pferde) am häufigsten auf. Bei allen Pferden wurde die Infektion mittels Nachweises von IgM sowie neutralisierenden Antikörpern gegen das WNV diagnostiziert, zwei euthanasierte Pferde waren zudem PCR-positiv. Die symptomatische Therapie beinhaltete vor allem nicht-steroidale Antiphlogistika oder Dexamethason sowie Infusionstherapie. Die Dauer des Klinikaufenthaltes betrug im Durchschnitt 7,5 Tage. Sieben Pferde erholten sich laut Besitzerangaben vollständig, für 2 Pferde war keine Information erhältlich.

Schlussfolgerungen und klinische Relevanz Die WNV-Enzephalomyelitis muss in Mitteldeutschland seit 2018 als Differentialdiagnose von im Sommer und Spätsommer auftretenden akuten neurologischen Erkrankungen ungeimpfter Pferdes in Betracht gezogen werden. Die beschriebenen Symptome sowie das Ergebnis der Therapie sind weitgehend deckungsgleich mit Berichten aus Nordamerika und anderen europäischen Ländern.

High exposure of West Nile virus in equid and wild bird populations in Spain following the epidemic outbreak in 2020

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 seropositive by both bELISA and virus microneutralization test [VNT]) was 38.3% (95%CI: 33.1-43.4). No IgM antibodies were detected in animals tested (0/243; 0.0%; 95%CI: 0.0-1.5) by capture-ELISA. The main risk factors associated with WNV exposure in equids were age (adult and geriatric), breed (crossbred) and the absence of a disinsection programme on the facilities. In wild birds, IgG antibodies against flaviviruses were found in 32.7% (56/171; 95%CI: 26.8-38.6) using bELISA, giving an individual WNV seroprevalence of 19.3% (95%CI: 14.3-24.3) after VNT. Seropositivity was found in 37.8% of the 37 species analysed. Species group (raptors), age (>1-year old) and size (large) were the main risk factors related to WNV seropositivity in wild birds. Our results indicate high exposure and widespread distribution of WNV in equid and wild bird populations in Spain after the epidemic outbreak in 2020. The present study highlights the need to continue and improve active surveillance programmes for the detection of WNV in Spain, particularly in those areas at greatest risk of virus circulation.

A One Health view of the West Nile virus outbreak in Andalusia (Spain) in 2020

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 Culex perexiguus 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 Cx. perexiguus and one pool of Culex pipiens were found. Serology of wild birds confirmed WNV circulation inside the affected villages, that transmission to humans also occurred in urban settings and suggests that virus circulation was geographically more widespread than disease cases in humans or horses may indicate. A high prevalence of antibodies was detected in blackbirds (Turdus merula) suggesting that this species played an important role in the amplification of WNV in urban areas. Culex perexiguus was the main vector of WNV among birds in natural and agricultural areas, while its role in urban areas needs to be investigated in more detail. Culex pipiens may have played some role as bridge vector of WNV between birds and humans once the enzootic transmission cycle driven by Cx. perexiguus occurred inside the villages. Surveillance of virus in mosquitoes has the potential to detect WNV well in advance of the first human cases.

Seroepidemiological Survey of West Nile Virus Infections in Horses from Berlin/Brandenburg and North Rhine-Westphalia, Germany

Following the introduction of the West Nile virus (WNV) into eastern Germany in 2018, increasing infections have been diagnosed in birds, equines, and humans over time, while the spread of WNV into western Germany remained unclear. We screened 437 equine sera from 2018 to 2020, excluding vaccinated horses, collected from convenience sampled patients in the eastern and western parts of Germany, for WNV-specific antibodies (ELISAs followed by virus/specific neutralization tests) and genomes (RT-qPCRs). Clinical presentations, final diagnoses, and demographic data were also recorded. In the eastern part, a total of eight horses were found WNV seropositive in 2019 (seroprevalence of 8.16%) and 27 in 2020 (13.77%). There were also two clinically unsuspected horses with WNV-specific antibodies in the western part from 2020 (2.63%), albeit travel history-related infections could not be excluded. None of the horse sera contained WNV-specific genomes. Eight horses in eastern Germany carried WNV-IgM antibodies, but only four of these showed typical clinical signs. These results underline the difficulty of detecting a WNV infection in a horse solely based on clinical signs. Thus, WNV circulation is established in the horse population in eastern Germany, but not yet in the western part.

West Nile virus transmission potential in Portugal

It is unclear whether West Nile virus (WNV) circulates endemically in Portugal. Despite the country’s adequate climate for transmission, Portugal has only reported four human WNV infections so far. We performed a review of WNV-related data (1966–2020), explored mosquito (2016–2019) and land type distributions (1992–2019), and used climate data (1981–2019) to estimate WNV transmission suitability in Portugal. Serological and molecular evidence of WNV circulation from animals and vectors was largely restricted to the south. Land type and climate-driven transmission suitability distributions, but not the distribution of WNV-capable vectors, were compatible with the North-South divide present in serological and molecular evidence of WNV circulation. Our study offers a comprehensive, data-informed perspective and review on the past epidemiology, surveillance and climate-driven transmission suitability of WNV in Portugal, highlighting the south as a subregion of importance. Given the recent WNV outbreaks across Europe, our results support a timely change towards local, active surveillance.

Lourenço et al. review historical data and quantify the transmission potential of West Nile virus in Portugal. They report a North-South divide in infection patterns, a higher ecological capacity in the south, and an increasing positive effect of climate change over the last 40 years.

West Nile virus in Spain: Forecasting the geographical distribution of risky areas with an ecological niche modelling approach

West Nile virus (WNV), a well-known emerging vector-borne arbovirus with a zoonotic life cycle, represents a threat to both public and animal health. Transmitted by ornithophilic mosquitoes, its transmission is difficult to predict and even more difficult to prevent. The massive and unprecedented number of human cases and equid outbreaks in Spain during 2020 interpellates for new approaches. For the first time, we present an integrate analysis from a niche perspective to provide an insight to the situation of West Nile disease (WND) in Spain. Our modelling approach benefits from the combined use of global occurrence records of outbreaks of WND in equids and of its two alleged main vectors in Spain, Culex pipiens and Cx. perexiguus. Maps of the climatic suitability for the presence of the two vectors species and for the circulation of WNV are provided. The main outcome of our study is a map delineating the areas under certain climatic risk of transmission. Our analyses indicate that the climatic risk of transmission of WND is medium in areas nearby the south Atlantic coastal area of the Cadiz Gulf and the Mediterranean coast, and high in southwestern Spain. The higher risk of transmission in the basins of the rivers Guadiana and Guadalquivir cannot be attributed exclusively to the local abundance of Cx. pipiens, but could be ascribed to the presence and abundance of Cx. perexiguus. Furthermore, this integrated analysis suggests that the WNV presents an ecological niche of its own, not fully overlapping the ones of its hosts or vector, and thus requiring particular environmental conditions to succeed in its infection cycle.

[Confirmed case of a West Nile virus infection in a horse with minimal neurological signs and a favorable clinical outcome]

West Nile virus (WNV) is a mosquito-borne viral pathogen of global importance and is considered to be the most widespread flavivirus. In Germany, first infections with WNV were detected in 2018 and it is expected for these to become more frequent in consequence to warmer winters followed by a rainy/humid springtime. WNV is maintained in an enzootic cycle between ornithophilic mosquitoes and certain wild bird species. Humans and horses are so-called "dead-end hosts" of a WNV infection. They frequently do not fall ill, however occasionally develop overt infections ranging from mild febrile symptoms (so-called "West Nile fever") up to severe encephalitis with fatal outcome. Therefore, it is important to recognize the clinical signs and to be able to distinguish a WNV infection from other possible differential diagnoses. The presented case report highlights rather uncommon clinical signs of a WNV infection such as non-specific fever, anorexia, or colic-like symptoms. In addition, possible differential diagnoses as well as the treatment are discussed. The time course of neutralizing antibodies following natural infection is reported, showing high levels of antibodies 7 months following the infection. Finally, antibody measurements demonstrated a very good immunologic response following a single WNV vaccination.

West Nile and Usutu virus infections in wild birds admitted to rehabilitation centres in Extremadura, western Spain, 2017-2019

West Nile virus (WNV) is an emerging flavivirus transmitted generally by mosquitoes of Culex genus. It is maintained in an enzootic life cycle where birds act as reservoir hosts. Humans and horses are also susceptible to infection, and occasionally, they suffer from neurological complications. However, they do not transmit the virus to other vectors, behaving as dead-end hosts. Sporadic WNV outbreaks observed in horses and wild birds from Extremadura (western Spain) during 2016 and 2017 seasons prompted to carry out this survey in wild birds, focused on specimens coming from two wildlife rehabilitation centres. Between October 2017 and December 2019, samples from 391 wild birds, belonging to 56 different species were collected and analysed in search of evidence of WNV infection. The analysis of serum samples for WNV-specific antibodies by ELISA, whose specificity was subsequently confirmed by virus-neutralisation test (VNT) showed positive results in 18.23 % birds belonging to 18 different species. Pelecaniformes (33.33 %), Accipitriformes (25.77 %) and Strigiformes (22.92 %) orders had the higher seroprevalences. Remarkably, WNV-specific antibodies were found in a black stork for the first time in Europe. Analysis by real time RT-PCR in symptomatic birds confirmed the presence of WNV lineage 1 RNA in griffon vulture and little owls. Specificity analysis of ELISA positive and doubtful sera was performed by differential VNT titration against WNV and two other cross-reacting avian flaviviruses found in Spain: Usutu virus (USUV) and Bagaza virus (BAGV). Only four samples showed USUV-specific antibodies (1.04 %) corresponding to three species: Eurasian eagle-owl, griffon vulture and great bustard (first detection in Europe) whereas no samples were found reactive to BAGV. Differential VNT yielded undetermined flavivirus result in 16 samples (4.17 %). This is the first study carried out on wild birds from Extremadura (western Spain). It highlights the widespread circulation of WNV in the region and its co-circulation with USUV.

Spatial distribution and risk areas of foot and mouth disease in mainland China

Foot-and-mouth disease (FMD) is a severe infectious disease in animal, which affects regional economies and food security of many countries. A total of 109 FMD outbreaks in China (from 2010 to 2019) were assessed. To investigate whether the FMD outbreaks were significantly aggregated in China, spatio-temporal cluster analysis was performed. A MaxEnt model was established to identify high risk areas for FMD in China and to identify relevant risk factors. As a result, both the FMD serotype A and O had one cluster each. Roads density, isothermality, UV-B seasonality and railways density were identified as important factors that affect the occurrence of FMD serotype A. The minimum temperature of the coldest month contributed most to FMD serotype O outbreak, followed by railways density and markets distribution. This study may provide useful information for decision makers for the tailoring of a risk-based surveillance of FMD in China.

Serological evidence of co-circulation of West Nile and Usutu viruses in equids from western Spain

West Nile virus (WNV) is a mosquito-borne emerging virus in Europe with capacity to cause neurological complications such as encephalitis or meningoencephalitis in humans, birds or equids. In Spain, WNV is actively circulating in mosquitoes, birds and horses in different regions, but never has been deeply studied in Extremadura. Therefore, the aim of this study was to evaluate the seroprevalence of WNV in equids of those areas and to analyse the risk factors associated with exposure to the virus. A total of 199 out of 725 equids presented antibodies against WNV by competition ELISA (27.45%), while 22 were doubtful (3.03%). Anti-WNV IgM antibodies were detected in 16 equids (2.21%), and 3 animals were doubtful (0.41%). All ELISA-reactive positive/doubtful sera (N = 226) were further tested by micro-virus neutralization test (VNT), and a total of 143 horses were confirmed as positive for WNV, obtaining a seroprevalence of 19.72% in equids of western Spain. In addition, specific antibodies against USUV were confirmed in 11 equids. In 24 equids, a specific flavivirus species (detected by ELISA test) could not be determined. The generalized linear mixed-effects models showed that the significant risk factors associated with individual WNV infection in equids were the age (adults) and hair coat colour (light), whereas in USUV infections, it was the breed (pure). Data demonstrated that WNV and USUV are circulating in regions of western Spain. Given the high WNV seroprevalence found in equids from the studied areas, it is important to improve the surveillance programmes of public health to detect undiagnosed human cases and to establish a vaccination programme in equid herds in these regions.

Tick-Borne Encephalitis Virus and Its European Distribution in Ticks and Endothermic Mammals

Tick-borne encephalitis (TBE) is the most common viral tick-borne disease in Europe causing thousands of human infections every year. Available risk maps in Europe are solely based on human incidences, but often underestimate areas with TBE virus circulation as shown by several autochthonous cases detected outside known risk areas. A dataset of more than 1300 georeferenced TBE virus detections in ticks and mammals except for humans was compiled and used to estimate the probability of TBE virus presence in Europe. For this, a random forests model was implemented using temperature- and precipitation-dependent bioclimatic variables of the WorldClim dataset, altitude, as well as land cover of the ESA GlobCover dataset. The highest probabilities of TBE virus presence were identified in Central Europe, in the south of the Nordic countries, and in the Baltic countries. The model performance was evaluated by an out-of-bag error (OOB) of 0.174 and a high area under the curve value (AUC) of 0.905. The TBE virus presence maps may subsequently be used to estimate the risk of TBE virus infections in humans and can support decision-makers to identify TBE risk areas and to encourage people to take appropriate actions against tick bites and TBE virus infections.

Evidence of exposure to zoonotic flaviviruses in zoo mammals in Spain and their potential role as sentinel species

A serosurvey was carried out to assess emerging flavivirus exposure in zoo mammals in Spain and to determine the dynamics of seropositivity in species that were longitudinally sampled during the study period. Sera from 570 zoo animals belonging to 120 mammal species were collected at ten zoos (A-J) in Spain between 2002 and 2019. Twenty-one of these animals, belonging to ten different species, were sampled longitudinally at four of the zoos during the study period. Antigenically-related flavivirus antibodies were detected in 19 (3.3 %; 95 %CI: 2.0-5.2) of the 570 animals analyzed using bELISA. Seropositivity was observed in ten (8.3 %) of the 120 species tested. Five (23.8 %) of the 21 animals sampled more than once presented seropositivity in all samplings whereas seroconversion was only observed in one white rhinoceros (Ceratotherium simum). Flavivirus antibodies were found at six of the ten sampled zoos and in consecutive years between 2008 and 2018. Virus neutralization tests confirmed West Nile virus (WNV), Usutu virus (USUV) and tick-borne encephalitis virus (TBEV) infection in ten (1.8 %; 95 %CI: 0.7-2.8), five (0.9 %; 95 %CI: 0.1-1.6) and one (0.2 %; 95 %CI: 0.0-0.5) animal, respectively. Antibodies against Meaban virus (0 %; 95 %CI: 0.0-0.7 %) were not found in the tested sera. The results demonstrate WNV, USUV and TBEV exposure in zoo mammals, which may be of public health and conservation concern. Seropositivity to WNV and USUV was detected in regions where these viruses have not been reported previously. Anti-WNV antibodies found in zoo animals sampled in 2009 point to WNV circulation at least one year before the first outbreaks were reported in horses and humans in Spain. Our results indicate that zoo mammals could be useful sentinel species for monitoring emerging flavivirus activity in urban areas.

Serological Evidence of West Nile and Usutu Viruses Circulation in Domestic and Wild Birds in Wetlands of Mali and Madagascar in 2008

The geographical distribution and impact on animal and human health of both West Nile and Usutu viruses, two flaviviruses of the Japanese encephalitis complex, have been increasing during the past two decades. Both viruses circulate in Europe and Africa within a natural cycle between wild birds and mosquitoes, mainly from the Culex genus. We retrospectively analyzed sera from domestic and wild birds sampled in 2008 in two wetlands, namely the Inner Niger Delta, Mali, and the Lake Alaotra area, Madagascar. Sera were first tested using a commercial ID Screen West Nile Competition Multi-species ELISA kit. Then, positive sera and sera with insufficient volume for testing with ELISA were tested with a Microneutralization Test. In Mali, the observed seroprevalence in domestic birds was 28.5% [24.5; 32.8] _95%CI, 3.1 % [1.8; 5.2] _95%CI, 6.2% [3.4; 10.2] _95%CI and 9.8 % [7.3; 12.8] _95%CI, for West Nile virus (WNV), Usutu virus (USUV), undetermined flavivirus, and WNV/USUV respectively. Regarding domestic birds of Madagascar, the observed seroprevalence was 4.4 % [2.1; 7.9]_95%CI for WNV, 0.9% [0.1; 3.1] _95%CI for USUV, 1.3% [0.5; 2.8] _95%CI for undetermined flavivirus, and null for WNV/USUV. Among the 150 wild birds sampled in Madagascar, two fulvous whistling-ducks (Dendrocygna bicolor) were positive for WNV and two for an undetermined flavivirus. One white-faced whistling-duck (Dendrocygna viduata) and one Hottentot teal (Spatula hottentota) were tested positive for USUV. African and European wetlands are linked by wild bird migrations. This first detection of USUV—as well as the confirmed circulation of WNV in domestic birds of two wetlands of Mali and Madagascar—emphasizes the need to improve the surveillance, knowledge of epidemiological patterns, and phylogenetic characteristics of flavivirus in Africa, particularly in areas prone to sustained, intense flavivirus transmission such as wetlands.

Locally temperature - driven mathematical model of West Nile virus spread in Germany

West Nile virus (WNV) is an arthropod-borne virus (arbovirus) transmitted by the bites of infected mosquitoes. WNV can also infect horses and humans, where it may cause serious illness and can be fatal. Birds are the natural reservoir, and humans, equines and probably other mammals are dead-end hosts. In 2018, WNV occurred for the first time in Germany, affecting birds and horses. Seroconversion of an exposed veterinarian has also been reported. It is therefore of importance to evaluate the circumstances, under which WNV may establish in Germany as a whole or in particular favourable regions. In our current work, we formulate a dynamic model to describe the spreading process of West Nile virus in the presence of migratory birds. To investigate the possible role of migratory birds in the dissemination of WNV in Germany, we include the recurring presence of migratory birds through a mechanistic ordinary differential equations (ODE) model system. We also perform a sensitivity analysis of the infection curves. Seasonal impacts are also taken into consideration. As result, we present an analytical expression for the basic reproduction number R₀. We find that after introducing WNV into Germany, R₀ will be above the critical value in many regions of the country. Furthermore, we observe that in the south of Germany, the disease reoccurs in the following season after the introduction. We include a potential distribution map associated with WNV cases in Germany to illustrate our findings in a spatial scale.

Emerging Trends in the Epidemiology of West Nile and Usutu Virus Infections in Southern Europe

The epidemiology of West Nile (WNV) and Usutu virus (USUV) has changed dramatically over the past two decades. Since 1999, there have been regular reports of WNV outbreaks and the virus has expanded its area of circulation in many Southern European countries. After emerging in Italy in 1996, USUV has spread to other countries causing mortality in several bird species. In 2009, USUV seroconversion in horses was reported in Italy. Co-circulation of both viruses was detected in humans, horses and birds. The main vector of WNV and USUV in Europe is Culex pipiens, however, both viruses were found in native Culex mosquito species (Cx. modestus, Cx. perexiguus). Experimental competence to transmit the WNV was also proven for native and invasive mosquitoes of Aedes and Culex genera (Ae. albopictus, Ae. detritus, Cx. torrentium). Recently, Ae. albopictus and Ae. japonicus naturally-infected with USUV were reported. While neuroinvasive human WNV infections are well-documented, USUV infections are sporadically detected. However, there is increasing evidence of a role of USUV in human disease. Seroepidemiological studies showed that USUV circulation is more common than WNV in some endemic regions. Recent data showed that WNV strains detected in humans, horses, birds, and mosquitoes mainly belong to lineage 2. In addition to European USUV lineages, some reports indicate the presence of African USUV lineages as well. The trends in WNV/USUV range and vector expansion are likely to continue in future years. This mini-review provides an update on the epidemiology of WNV and USUV infections in Southern Europe within a multidisciplinary "One Health" context.

African swine fever emerging in China: Distribution characteristics and high-risk areas

African swine fever (ASF) is a highly contagious disease that currently has no specific treatment or vaccine. In August 2018, ASF entered China causing great economic losses. In this study, data on 98 ASF cases in China from August 1^st, 2018 to January 1^st, 2019 were collected and analyzed. Spatio-temporal cluster and directional distribution analysis were performed to characterize the distribution of ASF cases. High risk areas for ASF outbreaks in China were identified using the presence-only maximum entropy (MaxEnt) ecological niche model. The distribution of ASF cases from Aug 1^st, 2018 to Jan 1^st, 2019 in China showed a significant directional trend (northeast-southwest) (P < 0.05) and a spatio-temporal cluster was detected in northeast China. A risk map for ASF infection was developed and pig density was identified as the most important predictor for ASF outbreak. This work presents ASF risk zones in China and may provide useful information for the development of effective strategies for the prevention and control of ASF outbreaks.

Epidemiology and spatial distribution of bluetongue virus in Xinjiang, China

Bluetongue (BT) is a non-contagious disease affecting domestic and wild ruminants. Outbreaks of BT can cause serious economic losses. To investigate the distribution characteristics of bluetongue virus (BTV), two large-scale censuses of BTV prevalence in Xinjiang, China were collected. Spatial autocorrelation analysis, including global spatial autocorrelation and local spatial autocorrelation, was performed. Risk areas for BTV occurrence in Xinjiang were detected using the presence-only maximum entropy model. The global spatial autocorrelation of BTV distribution in Xinjiang in 2012 showed a random pattern. In contrast, the spatial distribution of BTV from 2014 to 2015 was significantly clustered. The hotspot areas for BTV infection included Balikun County (p < 0.05), Yiwu County (p < 0.05) and Hami City (p < 0.05) in 2012. These three regions were also hotspot areas during 2014 and 2015. Sheep distribution (25.6% contribution), precipitation seasonality (22.1% contribution) and mean diurnal range (16.2% contribution) were identified as the most important predictors for BTV occurrence in Xinjiang. This study demonstrated the presence of high-risk areas for BTV infection in Xinjiang, which can serve as a tool to aid in the development of preventative countermeasures of BT outbreaks.

Arthropods as vectors of transmissible diseases in Spain

Different aspects related to globalization together with the great capacity of the arthropod vectors to adapt to a changing world favour the emergence and reemergence of numerous infectious diseases transmitted by them. Diptera (mosquitoes and sandflies), ticks, fleas and lice, among others, cause a wide spectrum of diseases with relevance in public health. Herein, arthropod-borne disease are reviewed, with special emphasis on the existing risk to contract them in Spain according to different parameters, such as the presence of arthropod and the circulation or the possible circulation of the causative agents.

Arthropods as vectors of transmisible diseases in Spain

Diferentes aspectos relacionados con la globalización junto a la gran capacidad de los artrópodos vectores para adaptarse a un mundo cambiante propician la emergencia y reemergencia de numerosos procesos infecciosos transmitidos por los mismos. Dípteros (culícidos y flebótomos), garrapatas, pulgas y piojos, entre otros, provocan un variado espectro de enfermedades con gran importancia en Salud Pública. En esta revisión se repasan las diferentes afecciones transmitidas por artrópodos vectores, haciendo un especial hincapié en el riesgo existente para contraerlas en España en función de diferentes parámetros, como la presencia del artrópodo y la circulación o posible circulación de los agentes causales.