Serologic and molecular evidence for circulation of Crimean-Congo hemorrhagic fever virus in ticks and cattle in Zambia

Author summary Crimean-Congo hemorrhagic fever (CCHF) is a severe viral disease mainly transmitted by ticks. Effective prophylactics and therapeutics have not been established for this disease yet. While CCHF is endemic in Africa, information on the distribution and genetic diversity of CCHF virus (CCHFV) is quite limited in many Sub-Saharan African countries. In this study, we conducted serologic and molecular epidemiologic investigations for CCHFV infection in cattle and ticks in Zambia. Serologic screening revealed that 8.4% of cattle were tested positive for CCHFV-specific IgG. Hyalomma ticks infected with CCHFV were also identified by genetic screening. Phylogenetic analyses showed that one of the CCHFVs detected in Zambia was a genetic reassortant between African and Asian CCHFV strains. Currently, Zambia is considered CCHF-free country because CCHF cases have never been reported. However, the findings in this study indicate that CCHFV is maintained in Hyalomma ticks and occasionally transmitted to vertebrate hosts such as cattle in Zambia. Further epidemiologic studies and continuous monitoring of CCHFV infection should be implemented in the southern African region. Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne zoonosis with a high case fatality rate in humans. Although the disease is widely found in Africa, Europe, and Asia, the distribution and genetic diversity of CCHF virus (CCHFV) are poorly understood in African countries. To assess the risks of CCHF in Zambia, where CCHF has never been reported, epidemiologic studies in cattle and ticks were conducted. Through an indirect immunofluorescence assay, CCHFV nucleoprotein-specific serum IgG was detected in 8.4% (88/1,047) of cattle. Among 290 Hyalomma ticks, the principal vector of CCHFV, the viral genome was detected in 11 ticks. Phylogenetic analyses of the CCHFV S and M genome segments revealed that one of the detected viruses was a genetic reassortant between African and Asian strains. This study provides compelling evidence for the presence of CCHFV in Zambia and its transmission to vertebrate hosts.