Identification and molecular characterization of Rift Valley Fever virus, in Uganda

Abstract

Background: Rift Valley Fever (RVF) virus is a negative-sense, single stranded RNA virus, whose genome comprises of three segments, Large (L), Medium (M) and small (S). RVF is a vector-borne zoonotic disease which has caused serious economic losses to farmers, by killing thousands of their animals. Rift Valley Fever virus in Uganda was first detected in mosquitoes collected from Semuliki forest, in 1944. The country had its first outbreak of RVF in humans in 2016 in Kabale district, western Uganda. There was no human death reported. Methods and materials: This study was carried out in three districts of the country, all located in the cattle corridor, where the largest animal population is found. Whole blood samples were collected randomly from livestock (cattle, sheep and goats). RNA extraction was done using QIAamp Viral RNA Mini kit following the manufacturer's instructions. One-step RT-PCR was used to amplify 494 bp of L segment of RVF genome. Gel electrophoresis of the PCR products/amplicons was performed using 1% agarose gel in 0.5X TrisBorate EDTA (TBE) buffer and stained with Ethidium Bromide. Full genome sequencing of the positive samples is yet to be done to determine the circulating strain of RVF virus, in the country. Results: Out of 312 samples tested, only 5 samples tested positive for RVF virus (1.6%). All these positive samples were from bovine, but from three different districts (Kiruhura 2, Sembabule 2 and Gomba 1 sample respectively). Conclusion: This study indicates low prevalence of RVF in the study area. The results also indicate that the virus is circulating silently in the livestock population and the country is at a risk of getting an outbreak of RVF, any time when conditions become favorable for the virus to cross into human population.