STACHURSKI, F. | bioRxiv Science

bioRxiv2025

Phenology of questing Ixodes frontalis nymphs reveals a late-winter to early-spring activity peak

Although Ixodes frontalis is widespread across Europe, including urban and peri-urban habitats, several aspects of its biology remain undescribed. One such aspect is the population dynamics of its nymphal stage, which has so far been reported from limited sample sizes, preventing the identification of its peak abundance. To fill this knowledge gap, we conducted a year-long monthly survey at four locations in France representing three distinct climates. The sampling protocol--based on the flagging method performed under bamboo bushes where larvae of this species had previously been found--was designed to maximize the likelihood of capturing the nymphal stage. Based on the 400 nymphs collected during this survey, a clear peak of I. frontalis nymphs was observed around March (February to April) across all four sites, with an additional peak in August at one site. The population dynamics of the larval stage--based on semi-quantitative counts--showed the same previously described pattern, with a peak in late autumn. Twenty adults (11 females and 9 males) were also collected from March to December, but these data did not allow a clear identification of a peak abundance. Because several bird species--such as blackbirds, song thrushes, European robins, and Eurasian blackcaps--serve as feeding hosts for both I. ricinus and I. frontalis, and are also reservoirs for pathogens transmitted by these ticks, the implications of our findings for the eco-epidemiology of tick-borne diseases are discussed. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=84 SRC="FIGDIR/small/696149v1_ufig1.gif" ALT="Figure 1000"> View larger version (34K): org.highwire.dtl.DTLVardef@170abeforg.highwire.dtl.DTLVardef@2802b5org.highwire.dtl.DTLVardef@c9be48org.highwire.dtl.DTLVardef@eb8e4d_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsA sampling method for Ixodes frontalis nymphs was developed Four hundred nymphs were collected across four different sites in France through a monthly survey A clear peak was observed around March, with an additional peak in August at one site

ecology↗

bioRxiv2025

Phenology of Hyalomma marginatum in a site in southern French

Hyalomma marginatum tick establishment has been recorded in southern mainland France for around ten years. This two-host species is one of the main vectors of the Crimean-Congo haemorrhagic fever (CCHF) virus. Knowing the phenology of the tick is a prerequisite for a better understanding of its spread and of CCHF virus dispersal. A longitudinal study was carried out between 2016 and 2022 in a horse herd to determine the seasonal variations of H. marginatum infestation. In the study site, adult ticks started infesting their hosts from the beginning of March. Infestation peaked during the first weeks of May. At that period, on average, up to 4 or 5 ticks attached daily to each horse. Then, the infestation steadily decreased until the end of August. In this site, birds are parasitised by H. marginatum immatures (larvae and nymphs) in summer, from mid/late June to the end of September. The larvae are therefore not yet active when the migratory birds pass through in spring. Blackbird, Turdus merula, was the most heavily infested bird species: nearly two-thirds of the blackbirds examined in summer were parasitised by H. marginatum. It is suggested that this bird species could be a good sentinel host for monitoring the establishment of the tick in currently H. marginatum-free areas. To complete these surveys, an experimental study was carried out in quasi-natural conditions with engorged ticks placed in cages in the garrigue. It was shown that the nymphs moulted into adults within 3-4 weeks in July-August. However, they remain completely immobile in the litter, undergoing a behavioural diapause, until the following spring. On the other hand, almost all the nymphs released later, in September or October, died during the cold and rainy season. It was also observed that engorged females were able to survive the cold conditions up to 6-8 months before laying eggs. The study also suggested that there were predators of H. marginatum, likely ants and spiders, in the study site. The hosts monitored over all these years were not only infested by H. marginatum. The phenology of other tick species parasitizing horses (Dermacentor marginatus, Haemaphysalis punctata, Rhipicephalus bursa) and birds (Ixodes frontalis, I. ricinus, H. punctata) was also highlighted for this study site.

pathology↗