Abstract
BackgroundIn this report we describe the molecular and pathological characteristics of West Nile virus (WNV) infection that occurred during the summer and fall of 2018 in avian species and equines. WNV is reported in Israel since the 1950s, with occasional outbreaks leading to significant morbidity and mortality in birds, high infection in horses and humans, and sporadic fatalities in humans.MethodsAnimal and avian carcasses in a suitable condition were examined by post-mortem analysis. Tissue samples were examined for WNV by RT-qPCR and the viral load was quantified. Samples with sufficient material quality were further analyzed by Endpoint PCR and sequencing, which was used for phylogenetic analysis. Tissue samples from positive animals were used for culturing the virus in Vero and C6/36 cells.ResultsWNV RNA was detected in one yellow-legged gull (Larus michahellis), two long-eared owls (Asio otus), two domesticated geese (Anser anser), one pheasant (Phasianus colchicus), four hooded crows (Corvus cornix), three horses and one donkey. Pathological and histopathological findings were characteristic of viral infection. Molecular analysis and viral load quantification showed varying degrees of infection, ranging between 70–1.4 × 106 target copies per sample. Phylogenetic analysis of a 906-bp genomic segment showed that all samples belonged to Lineage 1 clade 1a, with the following partition: five samples from 2018 and one sample detected in 2016 were of Cluster 2 Eastern European, two of Cluster 2 Mediterranean and four of Cluster 4. Four of the positive samples was successfully propagated in C6/36 and Vero cell lines for further work.ConclusionsWNV is constantly circulating in wild and domesticated birds and animals in Israel, necessitating constant surveillance in birds and equines. At least three WNV strains were circulating in the suspected birds and animals examined. Quantitative analysis showed that the viral load varies significantly between different organs and tissues of the infected animals.
Highlights
In this report we describe the molecular and pathological characteristics of West Nile virus (WNV) infection that occurred during the summer and fall of 2018 in avian species and equines
We describe the molecular detection and characterization of WNV infection in birds and horses that were diagnosed at the Kimron Veterinary Institute (KVI), Bet Dagan, Israel, during and 2018, after more than a decade in which cases in these species were only sporadic
It is conceivable that migrating birds traveling along the Great Rift Valley, as well as horses living in the eastern part of the country, were affected, but such cases have not been reported to the KVI
Summary
In this report we describe the molecular and pathological characteristics of West Nile virus (WNV) infection that occurred during the summer and fall of 2018 in avian species and equines. WNV is reported in Israel since the 1950s, with occasional outbreaks leading to significant morbidity and mortality in birds, high infection in horses and humans, and sporadic fatalities in humans. Schvartz et al Parasites Vectors (2020) 13:528 species of birds, as well as horses and humans [1,2,3]. While migratory and domestic avian species serve as a natural virus reservoir, humans and horses are considered dead-end hosts [1, 3, 6]. WNV infection in vertebrates is mostly subclinical and may cause symptoms ranging from fever, headache (in humans), malaise and other flu like symptoms, to meningoencephalitis or flaccid paralysis. WNV was identified in all continents except for Antarctica, where its major vector is absent [9]; it is currently recognized as one of the most widespread arboviruses [9, 10]
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