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. 2021 Oct 30;14(1):561.
doi: 10.1186/s13071-021-05061-1.

The transmission ecology of Tahyna orthobunyavirus in Austria as revealed by longitudinal mosquito sampling and blood meal analysis in floodplain habitats

Jeremy V Camp  1   2 , Edwin Kniha  3 , Adelheid G Obwaller  4 , Julia Walochnik  3 , Norbert Nowotny  5   6
Affiliations

The transmission ecology of Tahyna orthobunyavirus in Austria as revealed by longitudinal mosquito sampling and blood meal analysis in floodplain habitats

Jeremy V Camp et al. Parasit Vectors. .

Abstract

Background: Tahyna orthobunyavirus (TAHV) is a mosquito-borne virus that may cause mild flu-like symptoms or neurological symptoms in humans. It is historically associated with floodplain habitats in Central Europe, and the mammalophilic floodwater mosquito, Aedes vexans, is thought to be the principal vector. There are few contemporary reports of TAHV transmission ecology within mosquitoes or their vertebrate hosts, and virus infections are rarely reported (and probably seldom diagnosed). The objectives of this study were to survey the mosquito population for TAHV in three floodwater habitats and describe host usage by the predominant floodwater mosquito species to potentially define TAHV transmission at these foci.

Methods: We performed longitudinal mosquito sampling along three major rivers in eastern Austria to characterize the mosquito community in floodplain habitats, and tested for the presence of TAHV in pools of mosquitoes. We characterized TAHV rescued from mosquito pool homogenate by sequencing. We surveyed mosquito host selection by analyzing mosquito blood meals.

Results: We identified TAHV in two pools of Ae. vexans captured along the Leitha River. This mosquito, and other floodwater mosquitoes, used large mammals (red deer, roe deer, wild boar) as their hosts. The sequence of the rescued virus was remarkably similar to other TAHV isolates from the region, dating back to the first isolate of TAHV in 1958.

Conclusions: In general, we confirmed that TAHV is most likely being transmitted by Ae. vexans, although the precise contribution of vertebrate-amplifying hosts to the ecological maintenance of the virus is unclear. The pattern of host selection matches the estimated exposure of the same large mammal species in the region to TAHV based on a recent serosurvey, but hares were also hosts at the site where TAHV was detected. We also confirm humans as hosts of two floodwater mosquito species, providing a potential mechanism for spillover of TAHV or other mosquito-borne viruses.

Keywords: Arbovirus; Austria; Blood meal analysis; Mosquito; Orthobunyavirus; Transmission ecology.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Map of eastern Austria showing collection sites (symbols) for mosquitoes along major rivers (blue lines). Symbols show sites along the Danube (diamonds), Leitha (triangles), and Morava (circles) rivers. Austria is shown in gray background, and its position relative to other countries in Europe is shown in the inset figure, where countries are marked with two-letter abbreviations (e.g., AT Austria, SK Slovakia, and HU Hungary are shown on the main map)
Fig. 2
Fig. 2
Mosquito abundance per trap-night in 3 years along three floodplains in eastern Austria, showing a all species and the three most abundant floodwater aedine species: b Aedes vexans, c Ochlerotatus sticticus, and d Aedes cinereus. The symbols mark the abundance per trap-night organized by the numeric week of each year: 2016 (circles), 2017 (triangles), and 2019 (squares). Trapping was performed from the middle of May (calendar week 20) until the middle of September (calendar week 37). The lines connect trap-nights and are colored by floodplain: Danube (red), Leitha (blue), Morava (green)
Fig. 3
Fig. 3
Maximum likelihood phylogenetic trees of the coding regions for Tahyna orthobunyavirus nucleocapsid protein (a), polyprotein (b), and partial RNA-dependent RNA polymerase (c) isolated from pools of mosquitoes. Two isolates from Austria (in bold text marked with black circles) are compared to historical isolates from Europe and China, and the reference sequence of La Crosse orthobunyavirus was used as an outgroup. Terminal branch names list the GenBank accession number, the species of mosquito, the country, the isolate number, and the year when known. The accession numbers for the two isolates from Austria are Austria/OadD806/2019 (S: MZ245724, M: MZ245726, L: MZ245728) and Austria/OadD823/2019 (S: MZ245725, M: MZ245727, L: MZ245729). The trees are inferred over 500 bootstraps using the GTR + I (a), GTR + G + I (b), and GTR + G (c) substitution models. The lengths of the branches in substitutions per site are indicated by the scale bar. Because 858 nucleotides were not sequenced from isolate Austria/OadD806/2019 (MZ245728, nucleotide positions 2357–3215), this region was removed from the other sequences for analysis, maintaining codons in-frame
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