Seroprevalence of Crimean-Congo Hemorrhagic Fever and Rift Valley Fever Viruses Among Ruminants in Nigeria: A Descriptive Epizootiological Analysis.

Crimean-Congo hemorrhagic fever (CCHF) and Rift Valley fever (RVF) are major zoonotic diseases, spread by arthropods, with livestock serving as amplifying hosts. Despite Nigeria's large ruminant population and robust cross-border animal trade, data on the seroprevalence of the viral agents causing these diseases remain limited. A longitudinal serological survey was conducted in five major livestock markets across Nigeria. A total of 3450 animals (cattle, sheep, and goats) were tested for Crimean-Congo hemorrhagic fever virus (CCHFV) and Rift Valley fever virus (RVFV) antibodies using ELISA. Data on species, age, sex, animal origin, and tick infestation were collected and analyzed. Overall seroprevalence was 27.1% (95% CI: 25.6-28.6) for CCHFV and 5.8% (95% CI: 5.1-6.7) for RVFV. Cattle showed the highest prevalence for both CCHFV (55.4%) and RVFV (11.2%), followed by sheep (17.4% and 2.9%) and goats (8.6% and 3.4%). Evidence of mixed exposure to both CCHFV and RVFV antibodies was detected in 8.2% of cattle, 0.7% of sheep, and 0.2% of goats. Seropositivity was higher in older animals, females, tick-infested animals, and those of Nigerian origin compared to imported animals. Market-level variation was observed, with Mubi livestock market showing the highest CCHFV prevalence (35.5%) and Illela livestock market the highest RVF prevalence (11.2%). The detection of con-current CCHFV and RVFV antibodies, alongside high CCHFV prevalence and detectable RVFV circulation among Nigerian livestock highlight the risk of zoonotic spillover, particularly in livestock markets with intense human-animal interaction.