Serologic Evidence of Crimean-Congo Hemorrhagic Fever Virus Exposure among Livestock and Farmers in the Democratic Republic of the Congo

Crimean-Congo Hemorrhagic Fever (CCHF) is a potential high-threat zoonotic disease caused by the Crimean-Congo hemorrhagic fever virus (CCHFV). Transmission of CCHFV occurs primarily through bites of infected Hyalomma ticks or via direct contact with the blood or tissues of infected animals or humans. This study presents a cross-sectional assessment of CCHFV seroprevalence and risk factors associated with occupational and environmental exposures among cattle and swine agricultural workers.

Nine provinces across the Democratic Republic of the Congo (DRC) were selected and collection took place from June 2023 to July 2024. Five herds per species in each province were randomly visited, and at each facility or herd, up to 20 animals were chosen for serum sampling and attached tick collection. In five provinces, farm workers present on the day of collection were enrolled. Detection of anti-CCHFV Immunoglobulin G (IgG) antibodies was assessed via an in-house nucleoprotein-based enzyme-linked immunosorbent assay (ELISA).

Among the 1,118 cattle surveyed across nine provinces 57.0% (95%CI: 54.1-59.9%) were seroreactive. Cattle from two provinces in the southeast, Tanganyika and Lualaba, had 94.6% (95%CI: 89.9-99.2%) and 90.7% (95%CI: 84.9-96.5%) reactivity, respectively. Among the 1,020 swine surveyed 13.4% (95%CI: 11.1-15.2%) were seroreactive. Among the 180 agricultural workers surveyed, 12.8% (95%CI: 7.9-17.6%) (23) were seroreactive for CCHF antibodies.

This serologic survey indicated that CCHFV is circulating in the DRC and the southeast provinces are particularly at risk for spillover and morbidity among humans. Though no human cases have been reported since 2008, surveillance for CCHF should be considered among veterinary professional and healthcare workers.