Geneva Health Forum 2024

Vector-borne diseases in Corsica: exploratory study of Sandfly populations

Not scheduled

15m

Geneva

Scientific poster Health and the environment, time for solutions

Description

Sandflies are haematophagous dipterans that are known since the 18th century as vectors of human and/or canine leishmaniasis, diseases that are currently considered neglected tropical diseases but are re-emerging in Europe and have major health worldwide implications. More recently, sandflies have been incriminated in the emergence of the Toscana virus (TOSV) around the Mediterranean basin. Corsica, a French Mediterranean island, is endemic for Leishmania infantum leishmaniasis, with some canine clusters still persisting. Moreover, a recent study shows a high level of TOSV circulation despite the absence of clinical cases. Regarding sandfly species in Corsica, Phlebotomus pernisiosus is considered to be the main vector of L. infantum and TOSV; The vector role of Ph. sergenti and Sergentomyia minuta remains to be determined. Despite this situation, the last papers have been published in the 1970s, and the ECDC lists Corsican data as missing.

The aim of our study is to describe sandfly populations in a restricted part of Corsica as exploratory bases.

Sandflies were caught using six CDC light-trap traps between April and November 2023 at altitude of 280m, 480m and 760m a.s.l. in six stations around Corte, in center of Corsica. The sandflies collected were counted and identified individually by dissection of the head and the genitalia and their observation under the microscope.
150 captures were made and 2095 sandflies caught (sex ratio = 1.74). According to literature, emergence occurred from mid-June to mid-October, with a peak in July and August. Ph. perniciosus (69%) and Se. minuta (29%) were the most abundant and were found in all the stations. Ph. sergenti (0.8%) was found at 280m and 480m altitude while Ph. mascittii (0.2%) was found in the three. The latter two had never been described in this area. Unfortunately, our data cannot be quantitatively compared with previous, as the method used were different.

Despite sampling weaknesses, our study shows a predominance of the main vector of leishmaniasis and TOSV, highlighting the importance of studying the circulation of these two pathogens and sand fly populations across the island. We cannot formulate any hypotheses about the mechanisms involved in the appearance of two species previously absent from the area, but this reinforces the need for more frequent monitoring of insect vector populations, even those that appear less mobile. Sandflies are known to be ubiquitous but prefer adaptation (speciation) to mobility, i.e. they are more likely to be transported by continental drift than by airplane travel. However, very little is known about their ecology, mainly about their soil life. In this period of major environmental changes, field studies must be carried out to complete this lack of knowledge and serve to anticipate the health crisis.

Thanks for CLIMOS project contribution