Viral dissemination and diagnostic insights from experimental infection of sheep with Crimean-Congo hemorrhagic fever virus.

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne orthonairovirus widely distributed across Asia, Africa, the Middle East, and Southern Europe, causing severe illness and hemorrhagic fever in humans. While sheep usually show no clinical symptoms, they develop viremia and can play a key role in transmitting the virus to ticks and humans. Despite their importance in transmission, our understanding of infection dynamics in these animals remains limited. To bridge this knowledge gap, we conducted a controlled study in which six Pomeranian Coarsewool sheep were experimentally infected with CCHFV, strain Kosovo Hoti, and monitored over 21 days. All sheep developed transient fever and viremia. Necropsies at 5-7 days post infection (dpi) revealed highest viral loads in liver, spleen, testicles, and lymphoid tissues. Seroconversion occurred by 7 dpi and virus-neutralizing antibodies were detectable by day 8. These findings enhance our understanding of CCHFV infection dynamics in sheep and will aid future research, including vaccine development.