Abstract
BackgroundFor over a decade, monitoring of West Nile virus (WNV) in Germany has consisted of a bird monitoring programme as well as a mosquito-based surveillance programme employing CO2-baited encephalitis vector surveillance (EVS) traps for mass trapping and screening of mosquitoes. In contrast to the EVS traps, the Reiter/Cummings type box gravid trap collects gravid female mosquitoes, which have already taken a blood meal, increasing the likelihood of being infected with pathogens. The traps can be equipped with a honey-baited Flinders Technology Associates® (FTA) card to encourage sugar feeding by the trapped mosquitoes. FTA cards contain nucleic acid preserving substances, which prevent the degradation of viral RNA in the expectorated mosquito saliva and allows for testing the card for flavivirus RNA. This study aimed to assess the suitability of the method for WNV surveillance in Germany as an alternative to previous methods, which are expensive, time-consuming, and predominantly target host-seeking populations less likely to be infected with WNV.MethodsIn the Thüringer Zoopark Erfurt, snowy owls (Nyctea scandiaca) and greater flamingos (Phoenicopterus roseus) died of WNV infections in July and August 2020. In response, five Reiter/Cummings type box gravid traps were positioned during the daytime on the 10th, 13th, and 16th of September in five different locations. The FTA cards and mosquitoes in the chamber were collected, kept in a cool chain, and further processed for virus detection using a modified generic flavivirus reverse transcription PCR.ResultsA total of 15 trappings during September collected a total of 259 female mosquitoes, 97% of which were Culex pipiens sensu lato, as well as 14 honey-baited FTA cards. Eight mosquitoes tested PCR-positive for WNV. Four FTA cards tested PCR-positive for mosquito-borne flaviviruses, two of which were confirmed as WNV, and the remaining two confirmed as Usutu virus.ConclusionThe suitability of the FTA cards in preserving viral RNA in the field and rapid turnaround time from collection to result is combined with a simple, cost-effective, and highly specific trapping method to create an arbovirus surveillance system, which circumvents many of the difficulties of previous surveillance programmes that required the analysis of mosquitoes in the laboratory.Graphical
Highlights
For over a decade, monitoring of West Nile virus (WNV) in Germany has consisted of a bird monitor‐ ing programme as well as a mosquito-based surveillance programme employing CO2-baited encephalitis vector surveillance (EVS) traps for mass trapping and screening of mosquitoes
11 mosquitoes (4% of all specimens) from four trapping positions tested positive for flavivirus Ribonucleic acid (RNA) with the generic flavivirus Reverse transcription polymerase chain reaction (RT-PCR) (Table 1)
After the sequence analysis, eight mosquitoes were positive for WNV lineage 2, and three were positive for European Usutu virus (USUV) lineages
Summary
For over a decade, monitoring of West Nile virus (WNV) in Germany has consisted of a bird monitor‐ ing programme as well as a mosquito-based surveillance programme employing CO2-baited encephalitis vector surveillance (EVS) traps for mass trapping and screening of mosquitoes. In contrast to the EVS traps, the Reiter/Cum‐ mings type box gravid trap collects gravid female mosquitoes, which have already taken a blood meal, increasing the likelihood of being infected with pathogens. West Nile virus (WNV) is a member of the family Flaviviridae and belongs to the genus Flavivirus [1]. WNV circulates in an enzootic cycle with birds as amplifying host and mosquitoes as vectors [2]. Before 2018, there was no extensive autochthonous WNV circulation detected in Germany in any host populations, human or animal. PCR screening of blood donations from endemic WNV areas is recommended but causes additional costs
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