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.

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.

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.

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.