# Serologic evidence of crimean-congo hemorrhagic fever virus exposure among livestock and farmers in the Democratic Republic of the Congo

## TL;DR

This study found high rates of Crimean-Congo Hemorrhagic Fever virus exposure in livestock and farmers in the Democratic Republic of the Congo, especially in the southeast, highlighting the risk of future outbreaks.

## Contribution

The study provides the first serologic evidence of CCHFV exposure in DRC livestock and agricultural workers, identifying high-risk regions.

## Key findings

- Over 57% of cattle and 13% of swine showed evidence of CCHFV exposure.
- Southeastern provinces Tanganyika and Lualaba had over 90% seroreactivity in cattle.
- 13% of agricultural workers had CCHFV antibodies, indicating human exposure.

## Abstract

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 direct contact with 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, swine, and 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%) 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.

This study investigated exposure to Crimean-Congo Hemorrhagic Fever virus (CCHFV), a tick-borne disease, in livestock and agricultural workers across nine provinces of the Democratic Republic of the Congo (DRC). Researchers tested over 1,100 cattle, 1,000 swine, and 180 farm workers for antibodies to CCHFV, which can indicate past infection. More than half of the cattle (57%) and 13% of the swine had evidence of exposure, with extremely high rates in the southeastern provinces of Tanganyika and Lualaba, where over 90% of cattle tested positive. About 13% of farm workers also showed signs of past infection. The findings reveal widespread circulation of CCHFV among animals and people, even though no human outbreaks have been reported in the DRC since 2008. The study also found limited use of protective gear and close daily contact between workers and livestock, highlighting the risk of future spillover events. These results underscore the need for improved surveillance, farmer education, and One Health strategies that integrate human, animal, and environmental health efforts to prevent emerging zoonotic threats.