Participatory risk assessment in support of the zoonotic disease surveillance system in Cameroon: the case of Ebola Virus Disease and Rift Valley Fever

Background Viral haemorrhagic fevers (VHFs) are a group of acute zoonotic diseases with high mortality and morbidity rates infecting both humans and animals. These diseases are endemic in tropical rainforests of central Africa and can lead to severe epidemics. Previous studies have identified Cameroon as a high-risk country, due to favourable ecoclimatic conditions and the presence of susceptible mammals and vectors that have been tested positive for viruses causing VHFs. However, the country has not yet reported any epidemics/epizootics of VHFs such as Rift Valley Fever (RVF) and Ebola Virus Disease (EVD). This research provides novel, context-refined knowledge of perceived risk factors and temporal patterns of RVF and EVD emergence in Cameroon, where epidemiological data on these diseases are limited. Methods The present work proposes a risk assessment of the emergence and transmission of these two zoonoses through the development of an integrated risk assessment tool for identifying high-risk periods and key risk factors. A mixed, semi-quantitative approach involving expert semi-structured interviews, and a monthly calendar was used for data collection. Expert-based risk evaluation was then compared to risk factors derived from the scientific literature. Results For RVF, the wettest months seem to pose the highest risk, with increased inter-animal transmission during livestock transhumance. Key spatial determinants identified by experts included rainfall, host density, reservoirs, vectors, and livestock movements. For EVD spillover risk, human activities and behaviours, land cover, and host density were also identified as critical. Convergences and divergences regarding expert-based and literature-based risk factors for RVF and EVD were observed, with variations concerning livestock trade and ethnic background respectively. The distinction is likely attributable to the differing approaches of contextualization and generalization employed respectively by the two sources of weighting. Conclusions This study shows that, even in regions with no documented disease history, an integrated approach combining expert knowledge and literature-based evidence enables meaningful disease risk assessment, generates novel and context-specific information, and supports the refinement of preventive strategies. The participatory visual tool introduced allows identification and quantification of putative zoonotic risk factors and their temporal dynamics, informing risk mapping, management, and communication.