Schulz et al. Parasites Vectors (2021) 14:342 https://doi.org/10.1186/s13071-021-04819-x Parasites & Vectors RESEARCH Open Access Detection of Crimean-Congo hemorrhagic fever virus in blood-fed Hyalomma ticks collected from Mauritanian livestock A. Schulz1, Y. Barry2, F. Stoek1, M. J. Pickin1, A. Ba2, L. Chitimia‑Dobler3, M. L. Haki2, B. A. Doumbia4, A. Eisenbarth1, A. Diambar2, M. Y. Bah4, M. Eiden1 and M. H. Groschup1* Abstract Background: Crimean‑Congo hemorrhagic fever virus (CCHFV) belongs to the genus Orthonairovirus (Nairovididae) and is a (re)emerging tick‑borne pathogen. It is endemic in most parts of Africa, Asia and southern Europe, and can cause severe hemorrhagic symptoms in humans, with high fatality rates (5–30%). Methods: Hyalomma ticks were collected from four diferent livestock herds (cattle and camels) in Mauritania in 2018. The tick species were determined morphologically and confrmed molecularly by using the cytochrome oxidase 1 gene marker. For the detection of CCHFV, ticks were tested individually by one‑step multiplex real‑time reverse‑ transcriptase quantitative polymerase chain reaction. The small segment of all positive samples was sequenced to determine the CCHFV genotype. Results: In total, 39 of the 1523 ticks (2.56%) collected from 63 cattles and 28 camels tested positive for CCHFV. Three Hyalomma species were identifed. Hyalomma rufpes had the largest proportion of positivity (5.67%; 16/282), followed by Hyalomma dromedarii (1.89%; 23/1214). No Hyalomma impeltatum tested positive (0%; 0/21). Positive ticks were found in only six out of 91 host animals. Viral sequence analysis revealed the presence of two diferent CCHFV lineages (Africa I and Africa III). Conclusions: In this study, 2.56% of Hyalomma ticks collected from camels and cattle in Mauritania tested positive for CCHFV. However, the true prevalence of CCHFV in unfed ticks may be lower, as a considerable number of ticks may have been passively infected during blood‑feeding by co‑feeding ticks or due to viremia of the host. The results indicate the need to track the actual area of circulation of this virus. Keywords: Crimean‑Congo hemorrhagic fever virus, Hyalomma species, Livestock, Epidemiology, Mauritania Background parts of Africa, southern Asia and southern Europe [1, Crimean-Congo hemorrhagic fever virus (CCHFV), 2]. Te virus is characterized by its high genetic diver- which is a member of the genus Orthonairovirus in the sity [3]. Hard ticks of the genus Hyalomma are consid- family Nairovididae, is an emerging zoonotic arthropod- ered to be the main vectors and reservoirs of CCHFV [4]. borne virus that causes Crimean-Congo hemorrhagic Most, if not all, of the various hosts of Hyalomma (rang- fever (CCHF) in humans. CCHFV is present in most ing from wildlife species to domesticated animals) can be infected with CCHFV, although they tend to develop *Correspondence: [email protected] only short-term viremia without clinical symptoms [5]. 1 Institute of Novel and Emerging Infectious Diseases, Friedrich‑Loefer‑ In contrast, CCHFV infections in humans can lead to Institut, Südufer 10, 17493 Greifswald‑Insel Riems, Germany severe hemorrhagic symptoms, with a high lethality rate Full list of author information is available at the end of the article © The Author(s) 2021. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/. The Creative Commons Public Domain Dedication waiver (http:// creat iveco mmons. org/ publi cdoma in/ zero/1. 0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Schulz et al. Parasites Vectors (2021) 14:342 Page 2 of 10 of up to 30% [4]. Seroepidemiological studies of diferent 13]. Te results presented here can contribute to a better livestock and wildlife species can provide a frst indica- CCHFV exposure risk analysis for local farmers, butchers tion of whether CCHFV is circulating in a region. Hence and other exposed groups in close contact with livestock seroepidemiology has become a widely used instrument in the surveyed sampling areas. However, this work is not to identify areas potentially at risk of endemicity of the intended to replace the large-scale, nationwide epidemio- virus [5, 6]. For direct virus detection in these risk areas, logical studies that are necessary for a comprehensive ticks collected in the course of feld studies are often and detailed risk analysis. screened for the presence of the virus. However, these fndings must be interpreted with caution. Te detection Methods of CCHFV in engorged ticks is only evidence of the pres- Collection sites ence of the virus—it does not imply vector competence Mauritania, a large country in West Africa, is mainly of a tick, or constitute a quantitative measure of the true located in the desert landscape of the Sahara, and has virus prevalence in an area, since passive contamination a low population density. Samples were collected in the of the tick from the blood of the host cannot be excluded region surrounding the capital Nouakchott and the town [7]. Unequivocal information on host-vector dynam- of Rosso. Camels were sampled at a livestock market with ics as well as vector competence can only be obtained a nearby slaughterhouse on the outskirts of Nouakchott. by complex experimental studies of tick-host transmis- In addition, one cattle herd was sampled at a dairy farm sion, which have to be conducted according to stringent 60 km east of Nouakchott near the small village Idini guidelines, as described by Gargili et al. [7]. According to (Trarza). Two other sampling sites for cattle and cam- World Health Organization data, West African countries, els, respectively, were located in the area surrounding including Mauritania, are considered highly endemic, Rosso (Trarza) in southwestern Mauritania. Te distance with a large annual incidence of human CCHF cases. between Nouakchott and Rosso is about 160 km (Fig. 1). Traditional husbandry is common in Mauritania, mean- ing that there is close contact between farmers and their Collection of samples livestock. Te frst evidence of human CCHFV infec- Hyalomma ticks were collected from a total of 28 cam- tion in Mauritania was reported in 1983 [8]. Moreover, els and 63 cattles from the four aforementioned herds. several serological studies on livestock revealed a high On average, about 17 ticks per animal were collected and seroprevalence, 15%, in small ruminants [9, 10] and up examined. Te highest number of ticks (53 specimens) to 67% in cattle [11], underlining the high endemic sta- from an individual animal were collected from a cattle in tus of the country. Despite those high seroprevalences, Idini, while the lowest number (two specimens) was col- the presence of CCHFV in ticks has not been system- lected from a cattle in Rosso. Blood samples were taken atically studied in Mauritania. Te frst comprehensive from most of the animals (Idini, cattle, n = 49; Nouak- survey was conducted in 1985 and included 2539 ticks chott slaughterhouse, camels, n = 13; Rosso, camels, collected from cattle, sheep, goats, camels and horses n = 15). No blood samples were obtained from the cattle [12]. Te samples were pooled and analyzed using the herd in Rosso. In total, 77 blood samples were collected complement fxation test, which showed 12/172 (6–9%) among the diferent herds. Te sampled animals were CCHFV-positive tick pools. Of the four analyzed tick mainly infested with ticks of the genus Hyalomma. Given species (Hyalomma rufpes, Hyalomma marginatum, that Hyalomma ticks are considered to be the main vec- Hyalomma impeltatum and Hyalomma dromedarii), tor of CCHFV and that the primary objective was to only H. rufpes pools were positive. In a second study, 378 detect as well as to characterize the virus, ticks of other engorged and non-engorged ticks of two diferent genera genera were not considered in this study. Te collected (Hyalomma and Rhipicephalus) were tested for the pres- ticks and sera were stored at − 70 °C for 5 months at ence of CCHFV. CCHFV was only detected in four Rhipi- the Ofce National de Recherche et de Développement cephalus evertsi evertsi collected from sheep, whereas all de l’Elevage in Nouakchott. Ethanol (90%) was added to of the Hyalomma ticks were negative [10]. the tick samples prior to their shipment to the Friedrich- Te main goal of this study was to obtain recent data Loefer-Institut, Germany. Subsequently, tick and blood on the circulation of CCHFV in selected livestock herds samples were stored in ethanol for 3 months before fur- and Hyalomma ticks in Mauritania. Special attention ther processing. was paid to the characterization of CCHFV genotypes and accurate tick species determination, since incorrect Morphological and molecular identifcation of tick species identifcation of tick species is considered to be one of All ticks were morphologically identifed using the iden- the primary reasons for misleading statements regard- tifcation keys of Apanaskevich et al. [14–16]. Individ- ing potential vector/reservoir species in the literature [7, ual ticks were homogenized in Bufer AVL (300 µl AVL Schulz et al.