A qualitative risk assessment of Crimean-Congo haemorrhagic fever in Nigeria: implications for One Health response

Abstract

Background Crimean-Congo Haemorrhagic Fever (CCHF) is a severe tick-borne viral disease. Increasing cases in West Africa suggest potential undetected circulation in Nigeria. Methods A One Health Joint Risk Assessment was conducted to identify transmission pathways and assess the likelihood and impact of human CCHF infections at the human–animal–environment interface in Nigeria. Risk framing involved developing structured questions for potential Crimean-Congo Haemorrhagic Fever virus (CCHFV) transmission scenarios. A scoping review was conducted and median seroprevalence values were reported. The likelihood, impact and data uncertainty for human infection scenarios were used for a qualitative estimation of risk. Results Human contact with infected livestock during farming, veterinary practices and exposure to ticks was identified as a key infection route. Most cases in Nigeria (66.7%) were identified via serology, with a median human seroprevalence of 6.1% and cattle seroprevalence of 30.2%. CCHFV has been isolated from Rhipicephalus ticks. Four risk assessment questions were defined and focused on veterinarians, abattoir workers, herders, wildlife rangers and healthcare workers. Animal-related professions had a moderate likelihood of infection. Conclusion Strengthening One Health surveillance, vector control and multisector infection prevention is crucial to reducing the risk of CCHF and averting future outbreaks.