Wesselsbron virus at the livestock-human interface: A practical guide to disease recognition and diagnosis.

Wesselsbron virus (WSLV) is a mosquito-borne Orthoflavivirus of the yellow fever virus (YFV) serocomplex, widely distributed across sub-Saharan Africa. It is neglected, and its true impact is likely underestimated. WSLV causes abortion, congenital malformations, and neonatal mortality in sheep, the primary recognized vertebrate host, but infections have also been documented in goats, cattle, camels, wildlife, and humans. The virus is maintained in complex cycles predominantly involving Aedes mosquitoes and incompletely defined domestic and wild vertebrate hosts. Direct infection via the placenta, milk, and accidental laboratory exposure have been documented. These non-vector routes coincide with routine husbandry in African pastoral and agropastoral systems, creating opportunities for exposure at the livestock-human interface. Severe clinical disease is best characterized in sheep, in which hepatitis, congenital abnormalities, abortion, and neonatal mortality predominate. Similar symptomatology was reported in camels, but causality has not yet been experimentally demonstrated. Human infections are sporadic, usually self-limiting, it can involve hepatic disease, and rarely neurological manifestations. Clinical diagnosis of Wesselsbron disease is challenging because symptoms and environmental circumstances overlap closely with Rift Valley fever. While there is no serological cross-reactivity between WSLV and RVFV, WSLV antibodies broadly cross-react with other viruses of the YFV serocomplex. Molecular assays have improved detection of acute infections, and recent experimental studies have clarified pathogenesis, transmission, and immune responses. This review provides a practical framework for recognizing WSLV infection, selecting appropriate diagnostic samples and assays, and deciding when WSLV should enter the differential diagnosis of Rift Valley fever-like disease in humans, ruminants, and camels. We highlight non-vector zoonotic transmission, improved surveillance, routine diagnostic inclusion, and targeted research to better define Wesselsbron disease in a One Health context.