Detection and Molecular Characterization of Rift Valley Fever Virus in Apparently Healthy Cattle in Uganda

Rift Valley fever (RVF) is a zoonotic disease caused by the Rift Valley fever virus (RVFV), affecting humans, livestock, and wild ruminants. This study aimed to characterize and assess the genetic diversity of RVFV strains circulating among livestock in Uganda. Blood samples were collected between January 2021 and May 2024 from apparently healthy cattle, goats, and sheep in four districts. The samples were first screened for RVFV antibodies using ELISA; antibody-positive samples were subsequently tested for viral RNA using reverse transcriptase quantitative PCR (RT-qPCR). The PCR-positive samples underwent targeted amplicon sequencing, and phylogenetic analyses of the small (S) and large (L) genome segments were conducted to determine viral lineages. Of the 833 ELISA-positive samples, 10 (all from cattle) tested positive for RVFV RNA using RT-qPCR. Consensus sequences were successfully generated for six S segments and one L genome segment. A phylogenetic analysis revealed that all sequences belonged to lineage C, showing close genetic similarity to RVFV strains previously identified in Uganda, Kenya, Sudan, Madagascar, and Saudi Arabia. Limited genetic diversity was observed at both the nucleotide and amino acid levels. The detection of RVFV in apparently healthy cattle suggests ongoing, low-level viral circulation in Uganda. These findings offer important insights for guiding RVF surveillance, control, and policymaking in the country.