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.

West Nile Virus Seroprevalence in Wild Birds and Equines in Madrid Province, Spain.

West Nile virus (WNV) is a re-emerging flavivirus, primarily circulating among avian hosts and mosquito vectors, causing periodic outbreaks in humans and horses, often leading to neuroinvasive disease and mortality. Spain has reported several outbreaks, most notably in 2020 with seventy-seven human cases and eight fatalities. WNV has been serologically detected in horses in the Community of Madrid, but to our knowledge, it has never been reported from wild birds in this region. To estimate the seroprevalence of WNV in wild birds and horses in the Community of Madrid, 159 wild birds at a wildlife rescue center and 25 privately owned equines were sampled. Serum from thirteen birds (8.2%) and one equine (4.0%) tested positive with a WNV competitive enzyme-linked immunosorbent assay (cELISA) designed for WNV antibody detection but sensitive to cross-reacting antibodies to other flaviviruses. Virus-neutralization test (VNT) confirmed WNV antibodies in four bird samples (2.5%), and antibodies to undetermined flavivirus in four additional samples. One equine sample (4.0%) tested positive for WNV by VNT, although this horse previously resided in a WN-endemic area. ELISA-positive birds included both migratory and resident species, juveniles and adults. Two seropositive juvenile birds suggest local flavivirus transmission within the Community of Madrid, while WNV seropositive adult birds may have been infected outside Madrid. The potential circulation of flaviviruses, including WNV, in birds in the Madrid Community raises concerns, although further surveillance of mosquitoes, wild birds, and horses in Madrid is necessary to establish the extent of transmission and the principal species involved.

Warm winters are associated to more intense West Nile virus circulation in southern Spain.

West Nile virus (WNV) is the most widely distributed mosquito-borne flavivirus in the world. This flavivirus can infect humans causing in some cases a fatal neurological disease and birds are the main reservoir hosts. WNV is endemic in Spain, and human cases have been reported since 2004. Although different studies analyse how climatic conditions can affect the dynamics of WNV infection, very few use long-term datasets. Between 2003 and 2020 a total of 2,724 serum samples from 1,707 common coots (Fulica atra) were analysed for the presence of WNV-specific antibodies. Mean (SD) annual seroprevalence was 24.67% (0.28) but showed high year-to-year variations ranging from 5.06% (0.17) to 68.89% (0.29). Significant positive correlations (p < 0.01) were observed between seroprevalence and maximum winter temperature and mean spring temperature. The unprecedented WNV outbreak in humans in the south of Spain in 2020 was preceded by a prolonged period of escalating WNV local circulation. Given current global and local climatic trends, WNV circulation is expected to increase in the next decades. This underscores the necessity of implementing One Health approaches to reduce the risk of future WNV outbreaks in humans. Our results suggest that higher winter and spring temperatures may be used as an early warning signal of more intense WNV circulation among wildlife in Spain, and consequently highlight the need of more intense vector control and surveillance in human inhabited areas.

Implications of migratory and exotic birds and the mosquito community on West Nile virus transmission.

BACKGROUND: Vector-borne diseases like West Nile virus (WNV) pose a global health challenge, with rising incidence and distribution. Culex mosquitoes are crucial WNV vectors. Avian species composition and bird community diversity, along with vector communities, influence WNV transmission patterns. However, limited knowledge exists on their impact in southwestern Spain, an area with active WNV circulation in wild birds, mosquitoes, and humans. METHODS: To address this, we conducted a comprehensive study investigating the contributions of migratory and exotic bird species to WNV transmission and the influence of mosquito community composition. RESULTS: Analysing 1194 serum samples from 44 avian species, we detected WNV antibodies in 32 samples from 11 species, four for the first time in Europe. Migratory birds had higher WNV exposure likelihood than native and exotic species, and higher phylogenetic diversity in bird communities correlated with lower exposure rates. Moreover, in 5859 female mosquitoes belonging to 12 species, we identified WNV competent vectors like Cx. pipiens s.l. and the Univittatus subgroup. Birds with WNV antibodies were positively associated with competent vector abundance, but negatively with overall mosquito species richness. CONCLUSIONS: These findings highlight the complex interactions between bird species, their phylogenetics, and mosquito vectors in WNV transmission. Understanding these dynamics will help to implement effective disease control strategies in southwestern Spain.

Detection of a new avian bornavirus in barn owl (Tyto alba) by pan-viral microarray.

A barn owl (Tyto alba) died with neurological signs compatible with a viral infection. After discarding other possible infections caused by circulating viruses in the area, analysis of the central nervous system using a pan-viral microarray revealed hybridization to canary bornavirus 2 (CnBV-2). Subsequent sequence analysis confirmed the presence of a virus sharing more than 83% identity with CnBV-2. Surprisingly, the new sequence corresponds to a new virus, here named Barn owl Bornavirus 1 (BoBV-1), within the Orthobornavirus serini species. Moreover, it is the first member of this species that has been detected in a non-passerine bird, indicating that Orthobornavirus serini species comprises viruses with a wider range of hosts than previously presumed. The use of this microarray has proven to be an excellent tool for viral detection in clinical samples, with capacity to detect new viral variants. This allows the diagnosis of a great range of viruses, which can cause similar disease symptoms and which identification by PCR methods might be tedious, probably unsuccessful and, in the long run, expensive. This platform is highly useful for a fast and precise viral detection, contributing to the improvement of diagnostic methods.

Re-Emergence of a West Nile Virus (WNV) Variant in South Spain with Rapid Spread Capacity.

West Nile Virus (WNV) is a mosquito vector-borne zoonosis with an increasing incidence in Europe that has become a public health concern. In Spain, although local circulation has been known for decades, until 2020, when a large outbreak occurred, West Nile Virus cases were scarce and mostly occurred in southern Spain. Since then, there have been new cases every year and the pathogen has spread to new regions. Thus, monitoring of circulating variants and lineages plays a fundamental role in understanding WNV evolution, spread and dynamics. In this study, we sequenced WNV consensus genomes from mosquito pools captured in 2022 as part of a newly implemented surveillance program in southern Spain and compared it to other European, African and Spanish sequences. Characterization of WNV genomes in mosquitoes captured in 2022 reveals the co-circulation of two WNV lineage 1 variants, the one that caused the outbreak in 2020 and another variant that is closely related to variants reported in Spain in 2012, France in 2015, Italy in 2021-2022 and Senegal in 2012-2018. The geographic distribution of these variants indicates that WNV L1 dynamics in southern Europe include an alternating dominance of variants in some territories.

La fiebre/encefalitis por virus West Nile: reemergencia en Europa y situación en España / West Nile fever/encephalitis: re-emergence in Europe and the situation in Spain

En los últimos años se ha producido un incremento en la incidencia y rango geográfico de algunas arbovirosis, de las cuales quizá la más destacable sea la fiebre/encefalitis por virus West Nile. Esta enfermedad no recibió demasiada atención hasta los graves brotes ocurridos entre 1996 y 1999 en Rumanía, Rusia e Israel. Pero el acontecimiento que provocó una atención sin precedentes fue su aparición en Nueva York en 1999. Desde entonces su incidencia no ha dejado de crecer, y su rango geográfico de ampliarse. En América se ha extendido de costa a costa y desde Canadá hasta Argentina. En Europa ha aumentado su incidencia allí donde ya había ocurrido, y, recientemente, afectado zonas donde nunca antes había sido observada. El presente artículo es una revisión sobre el virus, la enfermedad, y su situación en Europa, con especial referencia a España, donde en 2010 se produjeron casos clínicos humanos y veterinarios (AU)

Some arbovirosis have increased their incidence and geographic range in the past few years. This phenomenon has been particularly noticeable in the case of West Nile fever/encephalitis. This disease did not receive much attention until serious outbreaks occurred in Romania, Russia and Israel between 1996 and 1999. But the event drawing an unprecedented attention to this disease was its occurrence in New York in 1999. Since then its incidence and geographic range has not ceased to grow. In America it has extended from coast to coast and from Canada to Argentina. In Europe, the disease incidence has increased in areas where it had already been reported, and, recently, affected other areas where it had never been observed before. The present article is a review on the virus, the disease, and its situation in Europe, with special reference to Spain, where in 2010 human and veterinary cases were reported (AU)

West Nile o Nilo Occidental / West Nile or Nilo Occidental

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Virus West Nile Antonio Tenorio / No disponible

Tras casi dos décadas de aparente silencio en Europa, el virus West Nile (WNV), un virus de aves transmitido por mosquitos, reapareció en 1996 en Bucarest, asociado por primera vez a un brote epidémico de encefalitis. Desde entonces, se ha ido describiendo en la mayor parte de los países del sur de Europa, del próximo Oriente y del norte de África. En 1999, el virus apareció por primera vez en América, en los alrededores de la ciudad de Nueva York, desde donde se expandió rápida y progresivamente por América del Norte y Central, hasta llegar a detectarse, siete años más tarde, en Buenos Aires y provincias limítrofes en la Argentina. Sorprendentemente, mientras el virus está aún causando en los EE.UU. la peor epidemia conocida de enfermedad por WNV, produce sólo brotes autolimitados en los países de la cuenca del Mediterráneo. El control de las futuras epidemias por WNV y por otros virus relacionados dependerá, en gran medida, del conocimiento que pueda ahora extraerse sobre los factores ecológicos, ambientales y sociales que influyen en el diferente comportamiento epidémico de la infección a uno y otro lado del Atlántico (AU)

After a twenty years period without described activity, the virus West Nile (WNV), an arthropod borne virus, re-emerged in Bucharest in 1996, associated to an outbreak of encephalitis. Since then, the virus has been described in most of the southern countries in Europe, the middle Orient and northern Africa. In 1999 the virus was described by the first time in America, around the New York City. Since then, the WNV spread through North, Central and South America, being described in Argentina in2006. Surprisingly, whereas the virus is causing its worst known epidemics in America, it is associated to small outbreaks in the Mediterranean basin. The control of future epidemics due to WNV and other related viruses depends on the study of the ecological, ambient and social factors influencing the distinct epidemic behaviour of the virus in the Old World and in the New World (AU)