Integrated surveys of Rift Valley fever, yellow fever and dengue in Lobaye, Central African Republic

Background Confirmation by plaque reduction neutralization testing (PRNT) of concurrent cases of Rift Valley fever virus (RVFV), yellow fever virus (YFV) and dengue virus (DENV) in Safa village (Lobaye, Central African Republic, CAR) triggered a One Health investigation to assess human, animal, entomological and socio-environmental risk factors for arboviral transmission. Methods We conducted integrated epidemiological surveys, blood sampling in humans and domestic animals, larval and adult mosquito collections, and socio-anthropological interviews in Safa and the neighbouring village of Popoto located in Lobaye. Human sera were tested at the Institut Pasteur de Bangui (IPB) by qPCR for RVFV, YFV, DENV, CHIKV and West Nile virus (WNV), and also for YFV IgM by ELISA. Animals were screened for RVFV and other livestock pathogens. Immature and adult mosquitoes after identification were tested by qPCR for the three arboviruses. Results Among 432 human blood samples from both villages, all PCR analyses performed for arboviruses were negative. Regarding yellow fever testing by ELISA, five samples initially tested IgM positive at the IPB were subsequently sent to the WHO Regional Reference Laboratory (Institut Pasteur de Dakar, IPD, Senegal) for confirmation by PRNT. Four out of five samples were then confirmed positive for YFV. Entomological surveys showed the Breteau, House, and Container indices, exceeding WHO epidemic thresholds. Aedes aegypti and Ae. albopictus co-dominated breeding sites, mainly large outdoor water-storage containers. The qPCR assays for arboviruses in mosquito samples were negative. Among 116 animals, all RVFV PCR were negative. Finally, socio-anthropological findings revealed limited community awareness of arboviral diseases and persistent culturally rooted explanations of febrile illness. Conclusion The environmental conditions, vector indices and livestock health indicators during the investigation, reveal a high potential for arboviral transmission in Lobaye. Strengthened One Health surveillance, earlier alert activation, and reduction of outdoor Aedes breeding sites are urgently needed to mitigate future outbreaks.