One Health 17 (2023) 100622 Contents lists available at ScienceDirect One Health journal homepage: www.elsevier.com/locate/onehlt Dynamics of Crimean-Congo hemorrhagic fever virus in two wild ungulate hosts during a disease-induced population collapse Laura Carrera-Faja a, Johan Espunyes a, Jesús Cardells b, Xavier Fernández Aguilar a, Lola Pailler-García c, d, Sebastian Napp c, d, *, Oscar Cabezón a, c a Wildlife Conservation Medicine Research Group (WildCoM), Departament de Medicina i Cirurgia Animals, Universitat Autònoma de Barcelona (UAB), 08193 Bellaterra, Spain b Servicio de Análisis, Investigación y Gestión de Animales Silvestres (SAIGAS), Veterinary Faculty, Universidad CEU-Cardenal Herrera, Tirant lo Blanc Street 7, Alfara del Patriarca 46115, Valencia, Spain c Unitat mixta d'Investigació IRTA-UAB en Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), 08193 Bellaterra, Catalonia, Spain d IRTA, Programa de Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), 08193 Bellaterra, Catalonia, Spain A R T I C L E I N F O A B S T R A C T Keywords: Identifying the role that host species play in pathogen transmission and maintenance is crucial for disease Vector-borne disease control, but it is a difficult task, in particular for vector-borne and multi-host pathogens, and especially when Sarcoptic mange wildlife species are involved. This is the case for a Crimean-Congo hemorrhagic fever virus (CCHFV) hotspot in Mediterranean basin north-eastern Spain, where Iberian ibex (Capra pyrenaica) and wild boar (Sus scrofa) are involved, but their roles Iberian ibex Wild boar in disease transmission are unclear. In this context, we studied the dynamics of CCHFV transmission in these two Hyalomma spp. species during the collapse of an Iberian ibex population due to a sarcoptic mange outbreak. We carried out a Rhipicephalus bursa repeated cross-sectional study measuring the trends of CCHFV seroprevalence in Iberian ibex and wild boar and their abundances. In addition, we identified the tick species present in this area on the vegetation and on wild boars, and evaluated relevant meteorological factors. Results show that while the trends in CCHFV seropreva­ lence in Iberian Ibex and density of wild boars remained constant (p = 1.0 and p = 0.8, respectively), both the trends in Iberian ibex census and CCHFV seroprevalence in wild boars decreased significantly (p = 0.003 and p = 0.0001, respectively), and were correlated (Spearman's rank, 0.02 < p-adjusted<0.05). The correlation between the patterns of reduction of Iberian ibex abundance and the decrease of seroprevalence in wild boars suggests some sort of shared transmission cycle between the two species. Data from tick species in the area suggest a possible role of Rhipicephalus bursa in CCHFV transmission. The dynamics of CCHFV were unlikely caused by changes in meteorological variables such as temperature or water vapor pressure deficit. Further studies will be needed to confirm these hypotheses. 1. Introduction involved because information on morbidity, mortality, or infection susceptibility of those species is difficult to obtain [4]. Most emerging pathogens, including zoonotic agents, can infect Crimean-Congo hemorrhagic fever virus (CCHFV) is a vector-borne multiple species [1]. Identifying the role of host species in pathogen pathogen mainly transmitted by Hyalomma spp. ticks, which are in transmission in a particular system is crucial for disease control [2]. This expansion in southern Europe [5]. In humans, CCHFV infection can is particularly challenging for vector-borne and multi-host pathogens cause a fatal hemorrhagic systemic disease [6]. The natural cycle of since interactions among the pathogen, vectors, and multiple hosts add CCHFV involves ticks of different stages that feed on several domestic layers of complexity to these systems [3]. Understanding the trans­ and wild animal species, and occasionally on humans. Hyalomma spp. mission dynamics is even more difficult when wildlife species are larvae and nymph stages usually feed on small mammals such as * Corresponding author at: Unitat mixta d'Investigació IRTA-UAB en Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), 08193 Bellaterra, Catalonia, Spain. E-mail address: sebastian.napp@irta.cat (S. Napp). https://doi.org/10.1016/j.onehlt.2023.100622 Received 30 April 2023; Received in revised form 21 August 2023; Accepted 22 August 2023 Available online 23 August 2023 2352-7714/© 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by- nc-nd/4.0/). L. Carrera-Faja et al. One Health 17 (2023) 100622 lagomorphs, hedgehogs, or rodents, or on ground-feeding birds, while on viral replication and spread within the tick (mainly determined by adults mostly feed on wild and domestic ungulates [7]. Immature stages temperature), or through the effect of meteorological factors on tick of some Hyalomma spp. can occasionally feed on ungulates when small abundance. Therefore, we also evaluated whether changes in those mammals are not abundant [8]. Ticks acquire the virus through co- factors throughout the study period may have influenced the dynamics feeding or feeding on viremic hosts, and through transovarian and of CCHFV transmission in the PTiBNP. transstadial transmission. As Hyalomma spp. ticks become infected for life, they are considered both vectors and reservoirs of CCHFV [9]. 2. Methods Therefore, while other tick species have been attributed a role in CCHFV transmission, it is assumed that only Hyalomma spp. ticks are able to PTiBNP (40◦ 48′28”N, 0◦ 19′7″E) is a calcareous mountain range with maintain an active focus of CCHFV [9]. Since CCHFV infected animals highly complex orography characterized by valleys, ravines and steep are asymptomatic with short viremias, serological surveys are essential gradients. The main habitats are pine and oak forests with altitudes to investigate CCHFV eco-epidemiology in wildlife, define endemic ranging from 300 to 1442 m above sea level. The predominant ungulate areas, and assess the exposure of potential hosts [10]. species are Iberian ibex and wild boar whereas roe deer is found in much In Spain, by 2022, twelve Crimean-Congo Hemorrhagic Fever lower densities [15]. We selected all available serum samples of wild (CCHF) cases in humans have been diagnosed since the first one in 2013, boars (n = 288) and Iberian ibexes (n = 88) collected in the PTiBNP and CCHF is considered an emerging infectious disease [11]. In central between 2013 and 2022 as part of the routine wildlife disease surveil­ and southern Spain, red deer (Cervus elaphus) is considered an indicator lance in Catalonia. Some of these samples had been tested, and the re­ of CCHFV infection risk, and it is the species that presents the highest sults were published in Espunyes et al. [13]. No samples from Iberian CCHFV seroprevalences [12]. In contrast, in the northern and eastern ibexes were available between 2014 and 2017 due to a hunting ban Mediterranean regions of Spain (Catalonia and Valencian Community, because of the detection of sarcoptic mange. Samples were analyzed respectively), where red deer is absent or scarce, hotspots of CCHFV using the CCHF Double Antigen Multi-species ELISA kit (iDvet, Mont­ exposure in wild ungulates have also been detected [13,14]. A sero­ pellier, France), which has a sensitivity of 98.9% (CI95%: 96.8%–99.8%) logical study on CCHFV carried out between 2014 and 2020 in Catalonia and a specificity of 100% (CI95%: 99.8%–100%) [20]. Data on the detected a focus of high antibody seropositivity in Iberian ibex (Capra population trends of Iberian ibex and of wild boar in the PTiBNP were pyrenaica) in Ports de Tortosa i Beseit Natural Park (PTiBNP), with a lower provided by the DACC of the Government of Catalonia. Wild boar den­ seroprevalence in Eurasian wild boar (Sus scrofa) [13]. These two un­ sities (animals/km2) were estimated based on the method developed by gulates are the most abundant wild mammalian species that host adult Sáez-Royuela and Tellería using data from collective hunts [21]. Iberian ticks in the PTiBNP, while other species such as roe deer (Capreolus ibex censuses were obtained through total counts, except for 2016 and capreolus) or red deer are scarce and absent, respectively [15]. Anti­ 2017 when the counts could not be carried out in the whole area, and bodies against CCHFV were not detected in wildlife, including Iberian estimates were obtained by linear regression. ibex and wild boars, from areas of Catalonia far from this hotspot [13]. Annual CCHFV seroprevalences were grouped according to hunting Another study carried out in the Valencian region (to the south of Cat­ seasons (September– April) with their 95% exact confidence intervals. In alonia) detected two other hotspots of CCHFV [14]. A high seroposi­ order to evaluate whether the seroprevalences in Iberian ibex and wild tivity (> 90%) was detected in wild ruminants, in Iberian ibex in both boar followed any (increasing, decreasing, or unchanged) trend foci and in mouflon (Ovis aries musimon) which was present only in one throughout the study period, a chi-squared test for trend [22], was of the foci; while a much lower seroprevalence (<20%) was detected in carried out. Mann-Kendall tests were performed to evaluate the trends in wild boars. In these two CCHFV foci of the Valencian region, the sero­ the densities of Iberian ibex and wild boar [23]. Finally, considering the prevalences and the populations of Iberian ibexes and wild boars have non-parametric nature of the data, a Spearman's rank correlation test not fluctuated significantly in the last 10 years [14,16]. Those findings was carried out to evaluate a possible correlation between the seropre­ suggest that Iberian ibexes, wild boars and occasionally mouflons, are valences of CCHFV in wild boar and the densities of Iberian ibex. To involved in the CCHFV circulation in the eastern Mediterranean region. account for the small number of observations (six, i.e., 2016–2017 to However, little is known about the distribution and abundance of 2021–2022), the p-value was adjusted based on the exact distribution CCHFV-competent tick species in this region. [24]. All statistical analyses were carried out using R software version In 2014, an outbreak of sarcoptic mange was detected in Iberian ibex 4.2.1 [25], and packages tidyverse [26], binom [27] and trend [28]. in the PTiBNP surrounding area, presumably introduced by local live­ To assess whether meteorological factors may have impacted the stock [17]. Sarcoptic mange is a skin disease caused by Sarcoptes scabiei dynamics of CCHFV in the PTiBNP, we used a knowledge-driven mite, which excavates the superficial epidermal layers causing a cata­ modelling approach (i.e., based on the existing knowledge about the bolic systemic inflammatory disease that leads to high mortalities, causal relationships with the pathogen of interest) [29]. We selected especially in wild Caprinae populations [18]. The sarcoptic mange ambient temperature and water vapor pressure deficit in the atmosphere epidemic in the PTiBNP progressed slowly but ended up in an 86.1% (VPD) as the factors to be evaluated for their potential effect on the reduction of the Iberian ibex population by 2021 (Departament d'Acció dynamics of CCHFV transmission in the PTiBNP [19,30]. Ambient Climàtica, Alimentació i Agenda Rural (DACC), i.e., Department of temperature influences the replication and spread of the virus within Climate Action, Food and Rural Agenda, personal communication). ticks and also regulates tick development. VPD influences tick mortality Since the abundance of wild ungulates seems to have a significant and has been found to be more relevant in defining the niche of ixodid effect on the risk of exposure to CCHFV [19], this sarcoptic mange ticks such as H. marginatum than other water-related variables such as outbreak represented an interesting scenario to evaluate how changes in evapotranspiration or soil humidity [30]. Hourly temperature data for the community of hosts modulated the transmission of CCHFV. There­ the area (PTiBNP) and period of study (2009–2023) was obtained from fore, we designed a retrospective multi-year cross-sectional study to Copernicus Climate Change Service [31] and averaged to obtain mean evaluate the trends of CCHFV seroprevalence in both Iberian ibexes and temperatures by month, while monthly VPD values were obtained from wild boars, as well as their population trends between 2013 and 2022. TerraClimate (http://www.climatologylab.org/terraclimate.html, Understanding the dynamics of CCHFV in an area also requires knowl­ accessed June 2023). We also calculated accumulated temperature and edge about the structure of the local community of ticks, known or po­ VPD in the complete year and accumulated VPD in winter [30] for the tential vectors of CCHFV. Thus, we carried out a field study to identify hunting seasons 2016–2017 to 2021–2022. To evaluate the trends of the tick species present in the PTiBNP, particularly focusing on the those three measures, Mann-Kendall tests were carried out, while detection of CCHFV vectors. Moreover, some meteorological factors are possible correlations between those measures and the seroprevalences of known to influence the transmission of CCHFV, either through the effect CCHFV in wild boar, were evaluated by Spearman's rank correlation 2 L. Carrera-Faja et al. One Health 17 (2023) 100622 tests, with adjusted p-values [24]. = 1.00), and accumulated VPD in winter (tau = 0.33, p = 0.45). Sampling of questing ticks was performed by dragging a 1 × 1 m Moreover, none of them was correlated with the seroprevalence of white cloth through the vegetation in three different 1 km transects CCHFV in wild boars: annual accumulated temperature (rs = 0.26, 0.2 < [32], all in areas where both wild boar and Iberian ibex were known to p-adjusted<0.5), annual accumulated VPD (rs = 0.09, 0.5 < p-adjusted), be present. Furthermore, six (two per transect) carbon dioxide-based and accumulated VPD in winter (rs = 0.26, 0.2 < p-adjusted<0.5). traps (CO2 traps) baited with dry ice were placed on 50 × 50 cm white cloths, to target species with host-seeking behavior (e.g., adult 4. Discussion Hyalomma spp.) [33]. CO2 traps were placed at least 200 m far from each dragging transect and left for 2 h. Cloth-dragging and CO2 trapping were The epidemiology of CCHF is complex and spatiotemporally het­ performed three times in the same transects during May and July 2023. erogeneous since biotic (host-vector-pathogen) and abiotic (e.g., Moreover, we collected ticks from wild boars (n = 7) hunted by rangers climate, habitat) interactions vary among ecosystems [36]. Identifying from the PTiBNP as a part of a wild boar population control program, the main drivers for the transmission of CCHFV in different systems is during May and June 2023. Adults and nymphs were identified alive critical to implement measures to reduce the risk to people. after collection using 35× and 64× magnifying lenses and taxonomic Red deer is considered an indicator of CCHFV infection risk in keys [34]. Data from ticks collected on Iberian ibex from PTiBNP in extensive areas of central and southern Spain [12]. However, in the Varela-Castro et al. [35] is also displayed in a table for a more eastern Mediterranean ecoregion the density of red deer is low and, in comprehensive comparison. the PTiBNP, CCHFV circulation involved Iberian ibex and wild boar, although with different levels of seroprevalence [13]. Our repeated 3. Results cross-sectional study in the PTiBNP showed that the seroprevalence of CCHFV in Iberian ibex remained at 100% even though sarcoptic mange Throughout the study period, 100% of the Iberian ibexes tested had dramatically reduced its population. In contrast, the CCHFV seropre­ antibodies against CCHFV. Regarding wild boars, the seroprevalence valence in wild boars decreased significantly yet its density did not show gradually declined throughout hunting seasons (66.7% in 2016–2017 to any increasing or decreasing trend. In fact, the reduction in the sero­ 4.2% in 2021–2022; Table 1, Fig. 1). This trend in seroprevalence prevalence of CCHFV in wild boars was found to be significantly reduction was statistically significant (Х2 (df = 1) = 59.9, p < 0.0001). correlated to the decrease in the abundance of Iberian ibexes. This The census of Iberian ibexes also had a statistically significant correlation suggests a possible connection between the CCHFV trans­ decreasing trend (tau = − 0.64, p = 0.0028), but no statistically signif­ mission cycles in Iberian ibex and wild boar, potentially through the icant trend was observed for the density of wild boars (p = 0.80) or the sharing of common tick vectors. seroprevalence in Iberian ibexes (p = 1.0) (Fig. 1). However, there was a The influence of the community of ungulates on CCHFV transmission statistically significant (Spearman's) correlation (rs) between the sero­ was evidenced by the results of Cuadrado-Matías et al. [19], who found prevalences of CCHFV in wild boar and the abundance of Iberian ibexes that the abundance of hosts was the most influential determinant of the during the study period (rs = 0.942, 0.02 < p-adjusted<0.05). inter-annual variation in CCHFV exposure risk. However, the precise A total of 499 ticks were harvested from the vegetation, 250 by mechanism that explains the epidemiological scenario in the PTiBNP is dragging and 249 by CO2 traps. Among them, 367 (89.2%) were Rhi­ difficult to ascertain. Whether Iberian ibexes can develop a CCHFV picephalus bursa, while Haemaphysalis punctata, Rhipicephalus sanguineus viremia after the bite of an infected tick and then transmit the virus to sensu lato (s.l.) and Hyalomma marginatum were less frequent (Table 2). uninfected ticks — potentially amplifying the viral infection in para­ One single specimen of Dermacentor marginatus and another of Rhipice­ sitizing ticks — is not known. In that case, the reduction of the popu­ phalus pusillus were also found. lation of Iberian ibexes would have decreased the number of infected A total of 118 ticks were collected from wild boars, with Rhipice­ ticks available to transmit CCHFV to wild boars. The few CCHFV phalus bursa being the most abundant (44.9%) and present in all the experimental infections used to evaluate viremias in ungulates were individuals, followed by Rhipicephalus sanguineus (28.8%) and Hya­ carried out several decades ago in livestock species such as cattle and lomma marginatum (20.4%). Six Hyalomma lusitanicum (5.1%) and one sheep, and they reported short-term viremias (2–9 days) followed by the Dermacentor marginatus (0.8%) were also identified (Table 2). development of anti-CCHFV antibodies [10]. As indicated by several The results of the monthly temperatures and the monthly VPD values authors [9,10,37], further experimental infections are needed, including in the PTiBNP for the period 2009 to 2022 showed a rather regular in wild ruminants but also in wild boars, to determine their potential pattern (Fig. 2). None of the cumulative meteorological variables role as amplifiers of CCHFV. Even in the absence of viremic hosts, there showed any statistically significant trend: annual accumulated temper­ are other mechanisms that may explain the maintenance of CCHFV foci. ature (tau = − 0.33, p = 0.45), annual accumulated VPD (tau = − 0.07, p Tick co-feeding allows the transmission of the virus present in the saliva of an infected tick to uninfected ticks feeding nearby [38]. This mech­ anism has been thoroughly explored for tick-borne encephalitis virus Table 1 [39,40], but its importance for CCHFV transmission remains to be Seropositivity against CCHFV in Iberian ibex and wild boar in the Ports de determined [8]. Some tick species, rather than hosts, are considered the Tortosa i Beseit Natural Park by hunting season. Data is displayed by n◦ of true natural reservoirs of CCHFV. Competent tick species allow the positives / total; seroprevalence percentage (95% exact confidence interval), − replication of CCHFV in their tissues, which later enables the trans­ no samples available. Hunting seasons 2014–2015 and 2015–2016 are not stadial transmission of the virus from larva to nymph or from nymph to included in the table because there were no samples available. * Part of these adult [9]. Transmission from adult female ticks to their eggs (i.e., ver­ results were already published in Espunyes et al. (2021) [13]. tical transmission) is also possible, although this mechanism seems to be Season Iberian ibex Wild boar less efficient in the case of CCHFV [37]. If vertebrate hosts can only 2012–2013 13 / 13; 100% (75.3% - 100.0%) – develop short-term viremias at first exposure [37], a more likely 2013–2014 9 / 9; 100% (66.4% - 100.0%) – explanation for the correlation between the Iberian ibex population 2016–2017 4 / 6; 66.7% (22.3% - 95.7%) – decline and the decrease in the seroprevalence of CCHFV in wild boars 2017–2018* 16 / 16; 100% (79.4% - 100.0%) 23 / 47; 48.9% (34.1% - 63.9%) 2018–2019* 41 / 41; 100% (91.4% - 100.0%) 18 / 31; 58.1% (39.1% - 75.4%) would be that Iberian ibex is important for the maintenance of tick 2019–2020* 9 / 9; 100% (66.4% - 100.0%) 15 / 54; 27.8% (16.5% - 41.6%) vectors of CCHFV. Therefore, the knowledge about the local community 2020–2021 – 7 / 78; 8.8% (3.7% - 17.6%) of ticks and which species could act as vectors of CCHFV, is critical. 2021–2022 – 3 / 72; 4.2% (0.9% - 11.7%) It is accepted that Hyalomma spp. are the main vectors and reservoirs Total 88 / 88; 100% (95.9% - 100.0%) 66 / 288; 22.9% (18.2% - 28.2%) of CCHFV, and in Spain, the two established species are H. lusitanicum 3 L. Carrera-Faja et al. One Health 17 (2023) 100622 Fig. 1. A: Trends in the seroprevalences of CCHFV antibodies in Iberian ibexes and wild boars (with their 95% confidence intervals), in relation to Iberian ibex censuses for the period between 2009 and 2022 in Ports de Tortosa i Beseit Natural Park (PTiBNP). B: Trend in the census of wild boars for the same area and period. The dotted vertical line indicates sarcoptic mange introduction in the surrounding of PTiBNP (2014). Grey dashed line with asterisks in Iberian ibex census trend indicates the years when total animal counts were obtained through linear regression (with the previous and the next animal counts). Grey area indicates the study period. Table 2 Ticks collected from vegetation and wild boars during May and July 2023 (present study), and from Iberian ibex during 2011–2015 (Valera-Castro et al. [35]) in Ports de Tortosa i Beseit Natural Park (PTiBNP). Tick species Questing and host-seeking ticks Wild boars (n = 7) (%) Iberian ibex (n = 134) (%) (Results from Varela-Castro et al., (2018)) Dragging CO2-trap Total (%) Rhipicephalus bursa 206 239 445 (89.2%) 53 (44.9%) 601 (89.8%) Haemaphysalis punctata 28 4 32 (6.4%) – 23 (3.4%) Rhipicephalus sanguineus s.l. 13 2 15 (3.0%) 34 (28.8.%) 5 (0.8%) Hyalomma marginatum 2 3 5 (1.0%) 24 (20.4%) 1 (0.2%) Dermacentor marginatus – 1 1 (0.2%) 1 (0.8%) 11 (1.6%) Rhipicephalus pusillus 1 – 1 (0.2%) – – Hyalomma lusitanicum – – – 6 (5.1%) – Haemaphysalis sulcata – – – – 28 (4.2%) Total 250 249 499 118 669 and H. marginatum [34], but little information is available about their In contrast, H. marginatum was known to be present in the PTiBNP distribution in the eastern Mediterranean region of Spain. A recent study but only one specimen had been found in the 134 the Iberian ibexes reported a high burden of H. lusitanicum ticks in wild boars from the evaluated by Varela-Castro et al. [35]. Absence or low levels of metropolitan area of Barcelona, where this tick species was detected in H. lusitanicum and H. marginatum ticks in Iberian ibexes may also be more than one-third (33.6%) of the animals [41]. In addition, in 2022, associated to a low preference of Hyalomma spp. ticks for this host. That questing H. lusitanicum ticks were collected in 31 municipalities sur­ would be consistent with studies in other areas of Spain in which both rounding the city of Barcelona [42]. Our study is the first to report the H. marginatum and H. lusitanicum were hardly ever detected feeding on presence of H. lusitanicum in the PTiBNP although in low abundance – Iberian ibex despite its presence in the area [44,45]. Nonetheless, it six specimens parasitizing two wild boars. In fact, H. lusitanicum was not should be pointed out that all those studies on ticks collected from found in any of the 134 Iberian ibexes from the PTiBNP sampled be­ Iberian ibexes were carried out during the hunting season (October to tween 2011 and 2015 [35], likely because Lagomorpha is absent or February), while the adults of H. lusitanicum are found on hosts mainly present in very low densities in the main areas where Iberian ibexes are between April and October (with peaks in May–June and Septem­ present (DACC personal communication). Presence of H. lusitanicum has ber–October), and the adults of H. marginatum are found on hosts mainly traditionally been associated with the presence of wild rabbits and hares between March and November (peak in April–June) [43]. Other authors because they are the main hosts for the immature stages [43], although, report that, nowadays, adults of H. lusitanicum may be found feeding on occasionally, larvae and nymphs may also feed on the same hosts as ungulates throughout the entire year [8], which is consistent with the adults [8]. finding of Castillo-Contreras et al. [41], who detected H. lusitanicum 4 L. Carrera-Faja et al. One Health 17 (2023) 100622 Fig. 2. Monthly vapor pressure deficit (VPD) in kilopascal (kPa) (green) and temperature in Celsius (orange) from 2009 to 2022. Grey area indicates the study period between 2016 and 2022. The dotted vertical line indicates sarcoptic mange introduction in PTiBNP (2014). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) ticks in wild boars from areas close to Barcelona all year round. In the cannot be ruled out and deserves to be investigated. It has been gener­ case of wild boar, we found H. marginatum in 6 out of 7 animals (May to ally assumed that Hyalomma spp. ticks are crucial for CCHFV trans­ July 2023) suggesting a possible role in CCHFV transmission to wild mission, and that in their absence/low abundance, an active focus of boars. This finding might be related to the fact that these individuals CCHFV cannot be maintained, but actual knowledge is lacking, and were captured in an area where free-ranging domestic cattle are occa­ studies to address these issues are required [9]. sionally present, and H. marginatum is mainly associated with the pres­ Dermacentor marginatus was found to be the most abundant tick ence of cattle [43]. Studies on wild boars and environmental ticks from species in wild boars from natural areas of north-eastern Spain [53,54], other areas of the PTiBNP are needed to accurately evaluate the abun­ coinciding with other studies carried out in Mediterranean habitats dance and distribution of H. marginatum in this region. In any case, the [55]. More recently, a study on ticks on wild boars from the metropol­ data available points out to the absence or very low abundance of itan area of Barcelona showed that D. marginatus was the second most Hyalomma spp. ticks in Iberian ibexes of the PTiBNP [35], which does abundant species (infestation prevalence: 26.9%) after H. lusitanicum not appear to explain the 100% seroprevalence detected in this species. (33.6%), while R. bursa was scarce (0.2%) [41]. In the PTiBNP, Rhipicephalus bursa, on the other hand, accounted for nearly 90% of D. marginatus was also found in the Iberian ibexes although at low levels the ticks found on Iberian ibexes from the PTiBNP [35], and 44.9% and (1.6%) [35], and we found a single D. marginatus in a wild boar and 89.2% of the ticks found, respectively, in wild boar and vegetation in the another in the vegetation. Although D. marginatus has been shown to present study. Several experimental studies suggested that Rhipicephalus transmit CCHFV transovarially, its role as a competent vector is still not species play a certain role in the transmission of CCHFV [46,47]. In a clear [9]. Given the low burden of D. marginatus in Iberian ibexes, and study of cattle from across Uganda, 69.7% (292/419) of the animals had the limited evidence about its role as a vector of CCHFV, this tick species CCHFV antibodies but only one of the 1065 ticks collected on them was is unlikely to have played a significant role in CCHFV transmission in the of the genus Hyalomma, and was negative to CCHFV, while 5.9% (18/ PTiBNP. 304) of the Rhipicephalus pools were positive [48]. And, in the case of Haemaphysalis punctata was the third most abundant tick species in R. bursa, CCHFV has been found in unfed ticks, which is considered an Iberian ibex in the PTiBNP [35], and also the second most abundant tick unequivocal demonstration that the virus survived tick molting or was species in the environment. CCHFV has been found in H. punctata passed transovarially from the engorged female to the larvae via the collected from ungulates on several occasions [9], and recently, a study eggs [9]. Moreover, R. bursa ticks appear to be the main vector of CCHFV carried out in southern Russia detected CCHFV in one (n = 477) genotype VI (Europe 2) (recently re-classified as Aigai virus) in different H. punctata unfed specimen [56]. These findings indicate that countries of the Balkan region [49]. Interestingly, in a study carried out H. punctata can also be a potential vector of CCHFV although its role in in Greece in which 2000 ticks were collected from sheep and goats, most maintaining the virus is still uncertain. Europe 1 sequences were obtained from Rhipicephalus sanguineus s.l., If the transmission of CCHFV in Iberian ibex and wild boar in the while the majority of Europe 2 sequences were obtained from R. bursa PTiBNP are somehow interconnected, the contrast in the prevalence [50]. It is not clear whether CCHFV strains introduced into a region between the two species may be explained by a difference in the burden could adapt to new tick species and if that association between R. bursa of CCHFV-tick vectors, as seen for example for H. lusitanicum which is and genotype VI is driven by the competence of this tick species, or by found in lower numbers in wild boars compared to red deer [51]. The the abundance of R. bursa in the region [9]. As the efficiency of Rhipi­ lower burden of ticks in wild boars may be influenced by behavioral cephalus spp. ticks as vectors of CCHFV is still not clear, further exper­ features (e.g., ritual of taking mud baths to remove ectoparasites), or to a imental studies on vector competence are needed [50]. While R. bursa in preference for habitats with a lower number of ticks [19]. all its stages prefers ruminants, adult R. bursa ticks are also found in wild A recent study in southwestern Spain detected significant interan­ boars although in a lower burden [41,51,52], which is consistent with nual variations in CCHFV seroprevalence in wild boar in the absence of the findings of the present study. Therefore, the possibility of a major demographic changes in the abundance of this species [19]. connection between CCHFV transmission cycles in Iberian ibex and wild Meteorological factors may impact the transmission of CCHFV directly, boars with the involvement of R. bursa (rather than Hyalomma spp.) by the effect on the replication and spread of the virus within the tick 5 L. Carrera-Faja et al. One Health 17 (2023) 100622 (mainly determined by temperature), or indirectly, through the effect of Declaration of Competing Interest meteorological factors on tick abundance [30,52]. We therefore evalu­ ated whether changes in meteorological factors relevant to CCHFV The authors declare that they have no known competing financial transmission may have influenced the dynamics of CCHFV in the interests or personal relationships that could have appeared to influence PTiBNP. The pattern of temperature and VPD remained quite regular the work reported in this paper. throughout the study period, and the statistical evaluation of the cu­ mulative values of temperature and VPD suggests that meteorological Data availability factors cannot explain the reduction of CCHFV seroprevalence in wild boars. However, as ticks are responsive only to the microclimatic con­ Data will be made available on request. ditions, conclusions based on large-area analyses should be interpreted with care [57]. Acknowledgements An alternative explanation for the differences in the seroprevalences between Iberian ibex and wild boars is that independent transmission We are grateful to the Departament d'Acció Climàtica, Alimentació i cycles occur in these two host species. In other words, that the ticks Agenda Rural (Generalitat de Catalunya) for providing the samples from involved in CCHFV transmission in Iberian ibex and wild boars are not the wildlife surveillance program. the same, and therefore may be affected differently by changes in abiotic or biotic factors. References Our findings indicate that there are some differences in the tick communities parasitizing Iberian ibex and wild boars. However, given [1] M.E.J. Woolhouse, L.H. Taylor, D.T. 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