Crimean–Congo hemorrhagic fever (CCHF), the most widespread tick-borne viral human infection, poses a threat to global health. In this study, clinical samples collected through national surveillance systems were screened for acute CCHF virus (CCHFV) infection using RT-PCR and for exposure using ELISA. For any CCHF-positive sample, livestock and tick samples were also collected in the neighborhood of the confirmed case and tested using ELISA and RT-PCR, respectively. Genome sequencing and phylogenetic analyses were also performed on samples with positive RT-PCR results. In Eastern Senegal, two human cases and one Hyalomma tick positive for CCHF were identified and a seroprevalence in livestock ranging from 9.33% to 45.26% was detected. Phylogenetic analyses revealed that the human strain belonged to genotype I based on the available L segment. However, the tick strain showed a reassortant profile, with the L and M segments belonging to genotype I and the S segment belonging to genotype III. Our data also showed that our strains clustered with strains isolated in different countries, including Mauritania. Therefore, our findings confirmed the high genetic variability inside the CCHF genotypes and their introduction to Senegal from other countries. They also indicate an increasing CCHF threat in Senegal and emphasize the need to reinforce surveillance using a one-health approach.

Background: Crimean‐Congo haemorrhagic fever (CCHF), a disease of medical and veterinary importance in several countries including Senegal, is transmitted by ticks or exposure to infected body fluids. Severe human cases of CCHF were recently observed across Senegal suggesting modification of the endemicity area and the tick fauna. Objective: This study aims to investigate some aspects associated with the bioecology of ticks infesting livestock and their infection with CCHF virus (CCHFV) across three bioclimatic areas of Senegal. Methods: Ticks were collected between October 2020 and November 2022, from randomly selected cattle, goats and sheep in the Sahelian, Sudano‐Sahelian and Sudanian zones. They were screened for CCHFV RNA by RT‐PCR. Results: A total of 3632 animals were examined, and 35.3% (95% CI: 33.8–36.9) were found tick‐infested. The overall tick infestation rate was 81.7% (95% CI: 78.1–84.9) in cattle, 30.3% (95% CI: 28.2–32.5) in sheep and 24.1% (95% CI: 21.8–26.5) in goats. TIR differed per age, gender, host species and bioclimatic area. Overall, 7734 ticks belonging to 12 species and 3 genera were collected. The most abundant species included Rhipicephalus evertsi (32.7%) and Hyalomma impeltatum (20.1%). CCHFV was detected in 6 of the 1709 tested pools with an overall minimum infection rate (MIR) of 0.8‰. Infected ticks ( H. impeltatum and H. rufipes ) were collected mainly from the anogenital areas of sheep and cattle in the Sahelian and Sudano‐Sahelian zones. Conclusion: These updated data on ticks and CCHFV vectors in Senegal will be useful for the prevention and control of tick‐borne diseases.

: Crimean–Congo hemorrhagic fever (CCHF) is a lethal zoonotic disease transmitted through tick bites and contact with infected animals or humans. As CCHF continues to expand worldwide, we report on the first severe outbreak in Senegal (Podor, Saint-Louis region) in 2022. We conducted a comprehensive outbreak investigation after a confirmed CCHF human case in Podor. This included sample collections from humans, animals, and ticks from the household and surrounding area. Human and animal samples were tested by ELISA for antibodies to CCHF virus and by reverse transcription polymerase chain reaction (RT-PCR) for CCHF virus RNA, whereas tick samples underwent CCHF RT-PCR only. Positive RT-PCR samples underwent viral genome sequencing for genetic characterization. We determined three CCHF human cases, with two deaths, as well as virus circulation in 11 ticks and in livestock, with an overall seroprevalence of 42.5%. CCHF IgG antibodies were detected in human contact cases, showing its prior prevalence in the area. Phylogenetic analyses revealed high genetic diversity within CCHF genotypes, with existence of reassortants and cocirculation of two different isolates from various origins in Mboyo and Nenette villages, where human cases were detected. The data showed a correlation between the strains identified in humans and ticks in each village, showing two independent emergences in Podor. The outbreak in Podor was probably because of the high abundance of animal hosts in this sylvopastoral area, the diversity of tick populations with the presence of the main CCHF vectors, and the increasing prevalence of CCHF virus. The surveillance in this area needs to be strengthened.

Ticks are major vectors of numerous pathogens affecting both livestock and humans. In Senegal, data on the diversity of tick‐borne pathogens (TBPs) in ruminant‐associated ticks remain limited. In total, 1703 ticks were collected from goats, sheep, and cattle across three ecological zones of Senegal (Sudanian, Sahelian, and Sudano‐Sahelian). Tick species were identified morphologically, and 300 individuals were screened for 36 microorganisms using a high‐throughput microfluidic real‐time PCR system. DNA was successfully extracted and amplified from 289 ticks. The most abundant species were Rhipicephalus evertsi evertsi (32.3%), Hyalomma truncatum (19.6%), R. guilhoni (15.6%), H. rufipes (11.6%), and Amblyomma variegatum (11.0%). Among the screened ticks, 226 (78.9%) were positive for at least one microorganism. True pathogens of veterinary and/or zoonotic importance included Anaplasma ovis (30.8%), Coxiella spp. (23.9%), Rickettsia aeschlimannii (13.1%), Theileria spp. (11.1%), and Ehrlichia canis (4.8%), with sporadic detections of Anaplasma marginale , A. bovis , and Babesia spp. (0.3% each). In addition, non‐pathogenic Francisella ‐like endosymbionts (FLEs) were detected at high prevalence (37.4%) across all ecological zones. The presence of TBPs and/or endosymbionts was significantly associated only with the tick’s host in the multivariable logistic regression model. Ticks collected from goats (OR = 7.82; p = 0.024) and sheep (OR = 7.70; p = 0.015) were significantly more likely to be infected than those collected from cattle (reference group). A total of 96 cases of microorganism co‐occurrence were recorded across different tick species. Co‐infections were more frequent in ticks collected from the Sudano‐Sahelian zone (48.2%) and in those from sheep (32.0%). None of the detected microorganism species showed a significant associated with tick sex. This study represents the first large‐scale molecular survey of TBPs in ruminant‐associated ticks in Senegal, revealing both a high diversity of pathogens and a widespread presence of tick endosymbionts. While endosymbionts, such as FLEs, are not known to be pathogenic, their abundance may influence tick physiology and vector competence. The detection of zoonotic pathogens, such as E. canis and R. aeschlimannii , underscores the need to strengthen tick surveillance and investigate their potential public health implications.