Integrated surveillance, virus isolation and phylogenetic characterization of Crimean-Congo hemorrhagic fever virus in Central Kazakhstan.

This study investigated the circulation of Crimean-Congo hemorrhagic fever virus (CCHFV) among livestock and ixodid ticks in the Karaganda and Ulytau regions of Central Kazakhstan and characterized the detected viral isolate. A targeted cross-sectional surveillance study was conducted during the spring-summer period of 2025 in the Shet, Aktogay, Ulytau, and Zhanaarka districts, as well as in the cities of Zhezkazgan, Satpayev, and Karazhal, selected because of pasture-based livestock management, livestock movement routes, and ecological suitability for ixodid tick populations. In total, 700 whole blood and 700 serum samples were collected from cattle and small ruminants. Additionally, 127 ticks were collected by flagging, direct removal from animals, and manual sampling and were identified morphologically. CCHFV RNA was detected using RT-qPCR, while anti-CCHFV IgG antibodies were detected by ELISA. Virus isolation was performed in BHK-21/13, Vero, CV-1, and MARC-145 cell lines. Viral RNA was not detected in livestock blood samples; however, one of eight tick pools collected in the Mibulak rural district tested positive by RT-qPCR. Anti-CCHFV IgG antibodies were detected in eight serum samples, including four originating from the same locality. A pronounced cytopathic effect was observed in BHK-21/13 and Vero cells on days 4-5 post-infection. Phylogenetic analysis of the S segment demonstrated that isolate CCHF/2025/Mibulak/KZ belongs to the Asia-2 genotype and clusters with strains previously reported from China, Kazakhstan, and Uzbekistan. Taken together, these findings support evidence of localized CCHFV circulation in Central Kazakhstan and highlight the importance of sustained integrated One Health surveillance for early detection and prevention of human infection.