Co-circulation of West Nile virus and distinct insect-specific flaviviruses in Turkey

Abstract

BackgroundActive vector surveillance provides an efficient tool for monitoring the presence or spread of emerging or re-emerging vector-borne viruses. This study was undertaken to investigate the circulation of flaviviruses. Mosquitoes were collected from 58 locations in 10 provinces across the Aegean, Thrace and Mediterranean Anatolian regions of Turkey in 2014 and 2015. Following morphological identification, mosquitoes were pooled and screened by nested and real-time PCR assays. Detected viruses were further characterised by sequencing. Positive pools were inoculated onto cell lines for virus isolation. Next generation sequencing was employed for genomic characterisation of the isolates.ResultsA total of 12,711 mosquito specimens representing 15 species were screened in 594 pools. Eleven pools (2%) were reactive in the virus screening assays. Sequencing revealed West Nile virus (WNV) in one Culex pipiens (s.l.) pool from Thrace. WNV sequence corresponded to lineage one clade 1a but clustered distinctly from the Turkish prototype isolate. In 10 pools, insect-specific flaviviruses were characterised as Culex theileri flavivirus in 5 pools of Culex theileri and one pool of Cx. pipiens (s.l.), Ochlerotatus caspius flavivirus in two pools of Aedes (Ochlerotatus) caspius, Flavivirus AV-2011 in one pool of Culiseta annulata, and an undetermined flavivirus in one pool of Uranotaenia unguiculata from the Aegean and Thrace regions. DNA forms or integration of the detected insect-specific flaviviruses were not observed. A virus strain, tentatively named as “Ochlerotatus caspius flavivirus Turkey”, was isolated from an Ae. caspius pool in C6/36 cells. The viral genome comprised 10,370 nucleotides with a putative polyprotein of 3,385 amino acids that follows the canonical flavivirus polyprotein organisation. Sequence comparisons and phylogenetic analyses revealed the close relationship of this strain with Ochlerotatus caspius flavivirus from Portugal and Hanko virus from Finland. Several conserved structural and amino acid motifs were identified.ConclusionsWe identified WNV and several distinct insect-specific flaviviruses during an extensive biosurveillance study of mosquitoes in various regions of Turkey in 2014 and 2015. Ongoing circulation of WNV is revealed, with an unprecedented genetic diversity. A probable replicating form of an insect flavivirus identified only in DNA form was detected.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-017-2087-7) contains supplementary material, which is available to authorized users.

Uranotaenia unguiculata Edwards, 1913 are attracted to sound, feed on amphibians, and are infected with multiple viruses

“…The flavivirus RNA-positive pool of males displayed closest sequence identity (100%) to a published sequence that was detected in Ur. unguiculata from Turkey (GenBank: KU958167) [ 15 ]. The presence of the DNA form of the sequence was confirmed by PCR amplification from the RNA extract (i.e.…”

“…Herein we report a potentially endogenous flavivirus-derived genomic sequence, identical to the sequence reported by others in Ur. unguiculata [ 15 ], possibly reflected an ancient association between Uranotaenia and flaviviruses [ 49 , 50 ]. In addition, we isolated and sequenced the genome of an alphamesonivirus which is widespread in the population at BSI.…”

“…Furthermore, nucleic acid from a potentially unique flavivirus has been identified from a population of Ur. unguiculata in Turkey [ 15 ]. Therefore, the potential of Ur.…”

Surveillance and Diagnosis of West Nile Virus in the Face of Flavivirus Cross-Reactivity

“…Since then several seroprevalence and mosquito surveillance reports confirmed the presence of WNV in Turkey ( Ergunay et al, 2013 , 2014 , 2015 ). A recent study was initiated to provide a risk-assessment of the circulation of mosquito borne flaviviruses in Turkey ( Ergunay et al, 2017 ), however, an integrated national surveillance plan is not yet in place.…”

Arboviral screening of invasive Aedes species in northeastern Turkey: West Nile virus circulation and detection of insect-only viruses

“…Among mosquito-borne viral pathogens, West Nile virus (WNV) seems to be ubiquitous in Anatolia and Thrace regions, with several reported cases of human and equine infections [11–14]. Moreover, vector screening efforts have identified WNV in both Culex and Aedes mosquitoes in various regions [14–16]. So far, no human infections due to indigenous transmission of DENV, YFV, CHIKV or ZIKV have been documented in Turkey.…”