The potential role of scavenging flies as mechanical vectors of Lagovirus europaeus/GI.2

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The European rabbit (Oryctolagus cuniculus) populations of the Iberian Peninsula have been severely affected by the emergence of the rabbit haemorrhagic disease virus (RHDV) Lagovirus europaeus/GI.2 (RHDV2/b). Bushflies and blowflies (Muscidae and Calliphoridae families, respectively) are important RHDV vectors in Oceania, but their epidemiological role is unknown in the native range of the European rabbit. In this study, scavenging flies were collected between June 2018 and February 2019 in baited traps at one site in southern Portugal, alongside a longitudinal capture-mark-recapture study of a wild European rabbit population, aiming to provide evidence of mechanical transmission of GI.2 by flies. Fly abundance, particularly from Calliphoridae and Muscidae families, peaked in October 2018 and in February 2019. By employing molecular tools, we were able to detect the presence of GI.2 in flies belonging to the families Calliphoridae, Muscidae, Fanniidae and Drosophilidae. The positive samples were detected during an RHD outbreak and absent in samples collected when no evidence of viral circulation in the local rabbit population was found. We were able to sequence a short viral genomic fragment, confirming its identity as RHDV GI.2. The results suggest that scavenging flies may act as mechanical vectors of GI.2 in the native range of the southwestern Iberian subspecies O. cuniculus algirus. Future studies should better assess their potential in the epidemiology of RHD and as a tool for monitoring viral circulation in the field.
This study was performed within the scope of project LAGMED (www.lagmed.eu), supported by Fundação para a Ciência e Tecnologia, FCT (PRIMA/0003/2018) and PRIMA programme, an Art.185 initiative supported and funded under Horizon 2020, the European Union’s Framework Programme for Research and Innovation. This work was also co-funded by the European Regional Development Fund (FEDER) and Norte Portugal Regional Operational Programme (NORTE2020), under the PORTUGAL 2020 Partnership Agreement, and by the project NORTE-01-0246-FEDER-000063. The authors also acknowledge FCT research support via the Junior Researcher grant of Ana M. Lopes (CEECIND/01388/2017), the PhD grant of João Vasco Côrte-Real (DFA/BD/4965/2020), the post-doctoral grant of Nuno Santos (SFRH/BPD/116596/2016), the Principal Researcher grant of Pedro J. Esteves (CEECIND/CP1601/CT0005), the Assistant Researcher grant of Joana Abrantes (CEECIND/00078/2017), and projects CIISA UIDB/00276/2020, LA/P/0059/2020-Al4AnimalS and CESAM UID/AMB/50017-POCI-01-0145-FEDER-007638.