Rift Valley fever seroprevalence and associated factors in non-vaccinated livestock (cattle and small ruminants) in Arua, Lira and Apac districts, Uganda

Abstract

Rift Valley fever (RVF) is a zoonotic viral disease of major veterinary public health and economic importance, transmitted primarily by mosquitoes and associated with significant livestock losses and human infections. Despite its epidemic potential and its demonstrated endemicity in western Uganda, data on its seroprevalence and associated factors from northern Uganda remain limited. This study determined the seroprevalence of RVF and its associated factors in unvaccinated livestock in Apac, Arua, and Lira districts. A cross-sectional study was conducted in selected sub-counties of Apac, Lira, and Arua districts in northern Uganda. Blood samples were collected from 704 randomly selected unvaccinated livestock (cattle, goats, and sheep). Sera were tested for RVF IgG antibodies using a competitive ELISA (IDvet) kit. Data on animal and herd characteristics were collected through interviews of livestock owners using a structured questionnaire. A robust modified Poisson regression analysis was done to estimate prevalence ratios for the factors associated with RVF IgG seropositivity. RVF IgG seroprevalence was 28% (95% CI: 24.8–31.4). Seropositivity was highest in Arua (54.5%) compared to Apac (28.6%) and Lira (18.1%). Seropositivity was higher in cattle (31.3%) when compared with goats (23%). In multivariable analysis, cattle were more likely to be RVF seropositive than goats (aPR = 1.37, 95% CI: 1.06–1.76, p < 0.05), while indigenous breeds had significantly lower likelihood of seropositivity than cross breeds (aPR = 0.40, 95% CI: 0.29–0.56, p < 0.05). Animals with recent (in the past 8 weeks) illness had significantly higher likelihood for RVF seropositivity than animals without recent illness history (aPR = 3.66, 95% CI: 2.93–4.57, p < 0.05). There is substantial RVF seropositivity among livestock in northern Uganda, suggesting possible RVFV circulation. Ecological factors, livestock species, breed types, and recent illness history are associated with RVF seropositivity, underscoring the need for strengthened surveillance and targeted control strategies.