Mapping the risk of Rift Valley fever in Uganda using national seroprevalence data from cattle, sheep and goats

Abstract

Uganda has had repeated outbreaks of Rift Valley fever (RVF) since March 2016 when human and livestock cases were reported in Kabale after a long interval. The disease has a complex and poorly described transmission patterns which involves several mosquito vectors and mammalian hosts (including humans). We conducted a national serosurvey in livestock to determine RVF virus (RVFV) seroprevalence, risk factors, and to develop a risk map that could be used to guide risk-based surveillance and control measures. A total of 3,253 animals from 175 herds were sampled. Serum samples collected were screened at the National Animal Disease Diagnostics and Epidemiology Centre (NADDEC) using a competition multispecies anti-RVF IgG ELISA kit. Data obtained were analyzed using a Bayesian model that utilizes integrated nested Laplace approximation (INLA) and stochastic partial differential equation (SPDE) approaches to estimate posterior distributions of model parameters, and account for spatial autocorrelation. Variables considered included animal level factors (age, sex, species) and multiple environmental data including meteorological factors, soil types, and altitude. A risk map was produced by projecting fitted (mean) values, from a final model that had environmental factors onto a spatial grid that covered the entire domain. The overall RVFV seroprevalence was 11.39% (95% confidence interval: 10.35–12.51%). Higher RVFV seroprevalences were observed in older animals compared to the young, and cattle compared to sheep and goats. RVFV seroprevalence was also higher in areas that had (i) lower precipitation seasonality, (ii) haplic planosols, and (iii) lower cattle density. The risk map generated demonstrated that RVF virus was endemic in several regions including those that have not reported clinical outbreaks in the northeastern part of the country. This work has improved our understanding on spatial distribution of RVFV risk in the country as well as RVF burden in livestock.

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, 2018aNyakarahuka et al, , 2023aNyakarahuka et al, , 2023bNyakarahuka et al, , 2023cNyamota et al, 2023;Tumusiime et al, 2023b).…”

“…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). An ecological niche model for Uganda also suggested that Isingiro district was a high risk area and the authors recommended surveillance activities to be targeted in such areas (Tumusiime et al, 2023a). In comparison with Kenya’s IgG RVF cattle seroprevalence picture (an indication to previous exposure to RVF), Owange et al reported 13.1% (183/1396) in 2014 (Owange et al, 2014a), Nanyingi et al reported 33.3% (95% CI [6.7–60]) in 2017, Bett et al reported 37.10% (30.72 – 43.84) in 2018.…”

“…Both wildlife and livestock share common water sources, along the shores of Lake Mburo and the Kagera River which spans the district. Isingiro district has an estimated cattle, goats and sheep of population of 368,246, 422,108 and 88,621 respectively (UBOS, 2024) and human population of 486,360 based on projections from human 2014 census respectively (Tumusiime et al, 2023a;). Isingiro district has 35 lower administrative units (sub counties) with 18 where animal rearing is conducted.…”

“…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.…”

Public health and research ethics education: the experience of developing a new cadre of bioethicists at a Ugandan institution

“…Africa continues to face emerging global health problems, like outbreaks of Ebola and Marburg viruses [ 27 ], which require testing new medications and vaccines, but many ethical issues related to such studies remain unresolved [ 28 ]. In Uganda, the western and southwestern regions have experienced outbreaks of yellow fever [ 29 ], rift valley fever [ 30 ], measles [ 31 ], and the Ebola virus disease from border crossing with the neighboring Democratic Republic of Congo [ 32 ], creating a perfect environment that requires responses from public health experts and researchers. Furthermore, Uganda is facing an epidemiological transition in disease burden from communicable to non-communicable diseases [ 33 ].…”