Investigations on the occurrence of West Nile virus, Usutu virus and Sindbis virus RNA in avian louse flies (Diptera: Hippoboscidae) collected in Germany (2016-2022).

Abstract

Background: As living vectors, arthropods play a crucial role in the transmission of viruses, bacteria and parasites. Previous research on virus transmission has focussed mainly on the roles of mosquitoes and ticks, while the potential importance of other blood-sucking arthropods such as louse flies (Hippoboscidae) has been somewhat neglected. The aim of this study was to detect viruses in avian louse flies from Germany to assess whether they could be used as sentinel organisms for monitoring arboviruses with zoonotic potential.

Methods: We collected 1000 louse flies of the species Crataerina hirundinis, C. pallida, Ornithomya avicularia, O. biloba, O. fringillina, O. chloropus, Ornithophila metallica and Pseudolynchia canariensis in Germany and screened the samples via RT-PCR for West Nile virus (WNV), Usutu virus (USUV) and Sindbis virus (SINV), which are arboviruses with avian hosts as reservoirs.

Results: While WNV was not detected, we found one louse fly positive for USUV and one for SINV RNA, both of which belonged to the species O. avicularia (n = 279). Therefore, the detection rates for both USUV and SINV were 0.1% (95% CI 0.0-0.3%) in the total sample and 0.36% (95% CI 0.00-1.09%) in O. avicularia. For the sample that tested positive for SINV, the PCR results were confirmed by sequencing a 288-bp segment that encoded part of the virus's structural polyprotein.

Conclusions: This is the first time that USUV RNA and SINV RNA have been detected in louse flies. In addition, it is the first detection of human pathogenic viruses in the louse fly species O. avicularia. The results of this study indicate that louse flies should not be neglected as possible sentinels of viral pathogens with zoonotic potential in the sense of the One Health concept.