Abstract
The distribution and abundance of Phlebotomine sand flies north of the Alps is poorly known. In Belgium, Phlebotomus mascittii was reported only once in the early 2000s from two locations in the southeastern part of the country. During a VectorNet field survey in 2023, no sand flies were detected in the provinces of Liège, Luxembourg, and Namur. As an extension of this investigation, a brief survey was conducted in August 2024 across four localities in the province of Luxembourg, Belgium. Using 16 light trap-nights and one resting catch, a single male specimen of Ph. mascittii was captured in a light trap placed in a stable/house ruin at Beauregard, commune of Rouvroy. This finding confirms the presence of Ph. mascittii in Belgium, 22-23 years after its initial finding. This detection highlights the need for further investigation on sand fly occurrence in Belgium, to determine species diversity, distribution and abundance.
1 Introduction
Phlebotomine sand flies are abundant in the Mediterranean region but rare north of the Alps (Medlock et al., 2014; Prudhomme et al., 2024) where their distribution and abundance remains poorly understood. To address this gap, a field study was performed in 2023 in the context of the European network for medical and veterinary entomology VectorNet along a south-north transect from known sand fly-inhabited areas near the Alps to the Benelux (Risueño et al., 2024). This study led to the first detection of Phlebotomus (Transphlebotomus) mascittii Grassi, 1908, a suspected vector of Leishmania infantum, in several NUTS3 units (départements/counties) of France as well as in Luxembourg and in the adjacent county of Trier-Saarburg in Germany. In the same study, efforts to detect sand flies in Belgium (provinces of Liege, Luxembourg and Namur) and southern Netherlands (province of Zuid-Limburg) remained unsuccessful. While sand flies were so far never detected in the Netherlands, a single historical record exists for Belgium, with the collection of one specimen of Ph. mascittii in Sainte-Cécile (Florenville) in 2001 and two specimens of the same species in Rachecourt (Aubange) in 2002, both in the province of Luxembourg, south-east Belgium (Depaquit et al., 2005). Building on the VectorNet survey of 2023, we conducted a brief follow-up investigation in summer 2024 targeting a few localities in Belgium, province of Luxembourg for the presence of sand flies.
2 Materials and methods
Four localities were selected for sand fly trapping. The first locality (Sainte-Cécile) has been investigated in 2001 and in 2023. The second (Aix-sur-Cloie) was selected because of the proximity to a location where sand flies were detected in 2002. The remaining two localities (Meix-devant-Virton and Beauregard) were selected because of their proximity to Thonne-la-Long in the adjacent French county of Meuse where sand flies were collected in 2023 (Figure 1). At each locality, the most suitable trapping sites were selected based on environmental features favourable for sand flies, i.e. old barns preferably with beaten earth floor and with poultry or dogs nearby, cellars with beaten earth floor, stone walls, cliff bases or rocks, and to their accessibility (Table 1). The survey was conducted on 21-22 August 2024, primarily using light traps (LT) deployed overnight as per the method described by Schaffner and Weigand (2025). On one occasion a resting catch (RC) in holes of stone walls was performed using a hand-made mechanical aspirator. The LTs were placed indoors or outdoors, or at the interface indoors/outdoors (e.g. open barn, ruin with destroyed roof), at 0.5 to 1 m height. Sand flies were morphologically identified as described elsewhere (Schaffner and Weigand, 2025).
Location of sampling sites of our sand fly survey in Luxembourg province (red) of Belgium, 21–22 August 2024. White squares: no sand fly detected in 2024; Black square: sand fly detected in 2024; Black stars: sand flies detected in 2001–2002 (Depaquit et al., 2005); Black triangle: sand flies detected in 2023 (France; Risueño et al., 2024).
Citation: Journal of the European Mosquito Control Association 2025; 10.52004/2054930x-20251021
Maps source: Luxbel.be CC BY-SA 3.0 and © OpenStreetMap contributors.Characteristics of the sites where sand flies were surveyed in Belgium, province of Luxembourg, 21–22 August 2024.
Citation: Journal of the European Mosquito Control Association 2025; 10.52004/2054930x-20251021
Impression of the sites investigated for sand fly presence in Luxembourg province of Belgium, 21-22 August 2024. (A) Collection site of Phlebotomus mascittii: house/stable ruin at Beauregard (SFBE-013B); (B) Male specimen of Ph. mascittii and its specific genitalia (vignette) caught at Beauregard; (C) Base of limestone cliff at Meix-devant-Virton (SFBE-012B); (D) Barn with beaten earth floor and poultry at Sainte Cécile (SFBE-010A).
Citation: Journal of the European Mosquito Control Association 2025; 10.52004/2054930x-20251021
Photo credits: Anna Schneider.3 Results and discussion
A total of 16 LT-nights and one RC were conducted, yielding a single detection of Ph. mascittii (Table 1 and Supplementary Table S1; Figure 1). One male specimen (Figure 2B), stored in the microscopic slide collection of the National Museum of Natural History Luxembourg (collection number MNHNL57223) was caught at Beauregard (SFBE-013B) using a LT placed in a house and stable ruin characterised by partially destroyed roof and walls and with somewhat beaten earth floor (Figure 2A). No sand flies were detected in the other traps at the same locality, nor at the three other localities, despite the apparent suitable environment and similar weather conditions (Figure 2C–D). Beauregard is the site closest to Thonne-la-Long, France, where sand flies were recently found in 2023. Sainte-Cécile, which had previously yielded a specimen of Ph. mascittii in 2001, remained negative in this survey, as it did in 2023. This short survey confirms the presence of Ph. mascittii in Belgium, 22-23 years after its initial detection. The finding as well as the absence of detection at or close to the locations that were positive in 2001–2002 suggest a low abundance, which is in line with other findings of Ph. mascittii at similar latitudes (Oerther et al., 2020; Risueño et al., 2024; Schaffner and Weigand, 2025). This detection underscores the need for further studies on sand fly occurrence in Belgium to determine species diversity (i.e. if Ph. (Larroussius) perniciosus Newstead, 1911 also occurs), distribution and abundance, particularly in areas that are considered suitable for their presence e.g. around Antwerp, Bruges, Brussels, Liege, Mons, and Namur (Supplementary Figure S1, created based on Alten et al., 2016). Recent studies in neighbouring areas showed that sand flies are more widespread than previously known, up to more northern latitudes (Krüger et al., 2025; Risueño et al., 2024; Schaffner and Weigand, 2025). Also, in the context of climate change, they could spread further north and build up larger populations.
Supplementary material
Supplementary material can be found online at https://doi.org/10.6084/m9.figshare.28254155
Table S1. Detailed field data of Phlebotomine sand fly investigation in Luxembourg, 2024.
Figure S1. Model output showing the probability of presence of Phlebotomus mascittii in Belgium. Detail of the model output developed as in Alten et al. (2016).
Acknowledgements
We acknowledge VectorNet and its contracting agencies EFSA, the European Food Safety Authority, and ECDC, the European Centre for Disease Prevention and Control, for supporting FS in the context of a capacity building field training that was linked to this survey (Framework contract number EFSA/2023/OP/0009 (OC/EFSA/BIOHAW/2023/05) and specific contract VECTORNET3 EFSA SC 01). WVB, is a member of Outbreak Research Team of the Institute of Tropical Medicine. This Team is financially supported by the Department of Economy, Science, and Innovation of the Flemish government. We are grateful to William Wint (Environmental Research Group Oxford) for providing the Ph. mascittii suitability model output (Supplementary Figure S1) and to Jérôme Depaquit (University of Reims Champagne-Ardennes, Faculty of Pharmacy) and Alexander Weigand (National Museum of Natural History Luxembourg) for kindly lending trapping material. We thank all private ground and building owners who allowed us to access their propriety to place traps.
Conflict of interest
Francis Schaffner is editor-in-chief of the Journal of the European Mosquito Control Association; he had no influence in the review process and decision making on this manuscript. The other co-authors declare no conflict of interest.
Data availability
The detailed data that supports the findings of this study are available in the supplementary material of this article.
References
Alten, B., Versteirt, V., Van Bortel, W., Zeller, H., Wint, W. and Alexander, N.S., 2016. VBORNET gap analysis: Sand fly vector distribution models utilised to identify areas of potential species distribution in areas lacking records. Journal of Open Health Data 4(1): p.e5. https://doi.org/10.5334/ohd.26
Depaquit, J., Naucke, T.J., Schmitt, C., Ferté, H. and Léger, N., 2005. A molecular analysis of the subgenus Transphlebotomus Artemiev, 1984 (Phlebotomus, Diptera, Psychodidae) inferred from ND4 mtDNA with new northern records of Phlebotomus mascittii Grassi, 1908. Parasitology Research 95: 113–116. https://doi.org/10.1007/s00436-004-1254-x
Krüger, A., Crecelius, A., Fischer, D. and Hagen R.M., 2025. New records of Phlebotomus (Transphlebotomus) mascittii Grassi, 1908 in northern Rhineland-Palatinate (Diptera: Psychodidae, Phlebotominae). Contributions to Entomology: in press.
Medlock, J.M., Hansford, K.M., Van Bortel, W., Zeller, H. and Alten, B., 2014. A summary of the evidence for the change in European distribution of phlebotomine sand flies (Diptera: Psychodidae) of public health importance. Journal of Vector Ecology 39: 72–77. https://doi.org/10.1111/j.1948-7134.2014.12072.x
Oerther, S., Jöst, H., Heitmann, A., Lühken, R., Krüger, A., Steinhausen, I., Brinker, C., Lorentz, S., Marx, M., Schmidt- Chanasit, J., Naucke, T. and Becker, N., 2020. Phlebotomine sand flies in Southwest Germany: an update with records in new locations. Parasites and Vectors 13: 173. https://doi.org/10.1186/s13071-020-04058-6
Prudhomme, J., Depaquit, J. and Robert-Gangneux F., 2024. Phlebotomine sand fly distribution and abundance in France: A systematic review. Parasite 31: 45. https://doi.org/10.1051/parasite/2024045
Risueño, J., Bersihand, S., Bender. C., Cornen, T., De Boer, K., Ibáñez-Justicia A., Rey, D., Rozier, Y., Schneider, A., Stroo, A. Vanslembrouck, A., Van Bortel, W., Weigand, A., Zambianchi, D., Pérez Cutillas, P., Oerther, S., Braks, M., Wint, W.G.R., Berriatua, E. and Schaffner, F., 2024. A survey of Phlebotomine sand flies across their northern distribution range limit in Western Europe. Journal of the European Mosquito Control Association 42(2): 105–115. https://doi.org/10.52004/2054930x-20241008
Schaffner, F. and Weigand, A., 2025. Phlebotomine sand flies (Diptera: Psychodidae: Phlebotominae), the vectors of Leishmania parasites, found to be widely distributed in Luxembourg. Journal of the European Mosquito Control Association: in press. https://doi.org/10.52004/2054930x-20251019
