Detection of Sporadic Outbreaks of Rift Valley Fever in Uganda through the National Viral Hemorrhagic Fever Surveillance System, 2017–2020

Abstract

Rift Valley fever (RVF) is a zoonotic disease of public health and economic importance. Uganda has reported sporadic outbreaks of RVF in both humans and animals across the country, especially in the southwestern part of the “cattle corridor” through an established viral hemorrhagic fever surveillance system. We report 52 human cases of laboratory-confirmed RVF from 2017 to 2020. The case fatality rate was 42%. Among those infected, 92% were males and 90% were adults (≥ 18 years). Clinical symptoms were characterized by fever (69%), unexplained bleeding (69%), headache (51%), abdominal pain (49%), and nausea and vomiting (46%). Most of the cases (95%) originated from central and western districts that are part of the cattle corridor of Uganda, where the main risk factor was direct contact with livestock (P = 0.009). Other predictors of RVF positivity were determined to be male gender (P = 0.001) and being a butcher (P = 0.04). Next-generation sequencing identified the predominant Ugandan clade as Kenya-2, observed previously across East Africa. There is need for further investigation and research into the effect and spread of this neglected tropical disease in Uganda and the rest of Africa. Control measures such as promoting vaccination and limiting animal–human transmission could be explored to reduce the impact of RVF in Uganda and globally.

Exploring community-based reporting of livestock abortions for Rift Valley Fever surveillance in Uganda: A pilot study

“…Regarding brucellosis, goats had the highest prevalence than cattle. These findings align with previous research conducted in Uganda and Keny (Birungi et al, 2021; Kabami, 2023; Ndumu et al, 2021; Nyakarahuka et al, 2018a, 2023a, 2023b, 2023c; Nyamota et al, 2023; Tumusiime et al, 2023b).…”

“…The relatively lower IgM positivity is suggestive of less current circulation despite the confirmed presence of RVF in four districts of Isingiro, Mbarara, Rubanda and Kazo in the 16 th – 20 th epidemiological weeks (Kabami, 2023). The presence of RVF antibodies in Isingiro district could also be explained by previous outbreaks in 2018, 2020 (Nyakarahuka et al, 2023c). The nationwide seroprevalence study by Nyakaruhuka et al showed that RVF was circulating in over 37/135 districts across the five regions in Uganda (Nyakarahuka et al, 2023c).…”

“…Following univariate screening for farm level risk factors (S1 Table) with a cutoff of p<0.2 for inclusion in a multivariable model, we developed a multivariable model. Known biological risk factors (stage of pregnancy, animal host, history of animal movements, environmental conditions) were also forced into the multivariable model regardless of the univariate significance (Nyakarahuka et al, 2023c). The associations were assessed by odds ratios, with a 5% level for statistical significance.…”

“…However, the first laboratory confirmed cases from animals and humans were not reported until 2016 from Kabale District (Shoemaker et al, 2019). Since then there have been sporadic RVF outbreaks in different parts of the country and these have been investigated by Ministry of Health (MoH) and Ministry of Agriculture, Animal Industries and Fisheries (MAAIF)’s surveillance departments (Aceng et al, 2023; Birungi et al, 2021; Kabami, 2023; Nyakarahuka et al, 2018a, 2023c, 2023a; Tumusiime et al, 2023a, 2023c). However, RVF surveillance is typically only carried out responsively after outbreaks that have already led to the loss of human lives or livestock.…”

Emerging tickborne viruses vectored by Amblyomma americanum (Ixodida: Ixodidae): Heartland and Bourbon viruses

“…Disease in young sheep, goats, and cattle is observed with the related Bhanja bandavirus (Hubalek 1987, Hubalek et al 2014). Severe epizootics in sheep, cattle, buffalo, and goats are associated with Rift Valley Fever virus, a phylogenetically related mosquito-borne phlebovirus (HRTV and DBV were formerly grouped with the phleboviruses) (Meegan et al 1979, House et al 1992, Madani et al 2003, Chevalier et al 2010, Hubalek et al 2014, Nyakarahuka et al 2023). Of the thogotoviruses, only the eponymous THOV has been shown to produce disease in animals, causing leukopenia in cattle and abortion and fever in sheep (Davies et al 1984, Sang et al 2006b).…”