Emergence of Crimean-Congo Hemorrhagic Fever Virus in Eastern Senegal in 2022

Abstract

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.

Keywords: Crimean–Congo hemorrhagic fever virus; Eastern Senegal; human; reassortment; ticks.

Figure 1

Regions and locations of Crimean–Congo hemorrhagic fever virus detection in humans and ticks in 2022 in Eastern Senegal.

Figure 2

Maximum-likelihood trees of CCHFV strains based on the L (a), M (b), and S (c) segments. L, M, and S segments follow the genotype names described by Papa et al. [10]. Genotypes are identified by Roman numerals. All the newly characterized CCHF isolates from Senegal in 2022 are color-coded in red.

Figure 3

Similarity plot generated by SIMPLOT software version 3.5.1 based on the 3 genome segments. The tick strain (Koum_2022) was used as a query sequence, and isolates from Oman (OMAN_1997), Spain (SPN_2016), Senegal (SEN_1969 and SEN_1972), and Mauritania (MRT_1984) were used as representative parent sequences. The similarity score is expressed as percentage.

Figure 4

Scheme of genetic reassortment between CCHF genotypes. Each circle represents a different CCHF genotype. The 3 internal lines represent all genome segments according to their decreasing sizes (L, M, and S segments). The arrows indicate shared segments. The genotype of the tick strain (Koum_2022) was derived from reassortment events between the potential candidate strains.