Spatio-Temporal Dynamics of Crimean Congo Hemorrhagic Fever Virus Infection Using Animal Sentinel Herds in Senegal:...

Crimean-Congo Hemorrhagic Fever virus (CCHFV) is a zoonotic arbovirus of major public health, transmitted to humans and animals by ticks or animals infected. Although previous evidence of CCHFV circulation was reported in central and southeastern bioecological areas of Senegal, its spatial and temporal dynamics remain poorly understood. To investigate CCHFV activity, naïve sheep and goats were placed near human populations as sentinel herds in the areas from March 2021 to June 2024. Blood and tick samples were regularly collected from these animals. Sera were tested by ELISA for CCHFV antibodies, while ticks were screened by RT-PCR for CCHFV RNA. A total of 2,708 sera were tested and an overall seroconversion of 16.83% (95% CI: 14.46%-19.42%) was recorded. Variations in CCHFV infection rate (CCHFVIR) were no significant between central and southeastern zones, but highly significant between districts within each area. Goats were significantly more likely to be infected than sheep (OR = 1.47; 95% CI: 1.03-2.11; p = 0.035). The CCHFVIR was significantly higher during dry season (dry: 21.77%; 95% CI: 17.80%-26.17% vs. rainy: 13.08%; 95% CI: 10.30%-16.28%, p = 0.001). Seasonal fluctuations in tick vectors abundance appeared to closely correlate with seroconversion dynamics in sentinel herds, even if they are no tick pool positive to CCHFV by RT-PCR. This study showed permanent circulation of CCHFV in both areas, and suggest that rainfall patterns, host species and geographic location are key factors in CCHFV transmission risk. A One Health approach associating animal, human and environmental surveillances need to be implemented to control CCHF emergence and spread.