Seroprevalence and risk factors associated with brucellosis in humans and livestock in Nyagatare district of Rwanda.

BACKGROUND

Brucellosis is a significant but under-reported bacterial zoonosis in Rwanda. Despite recognition as one of Rwanda's top six priority zoonotic diseases in 2019, comprehensive epidemiological data linking human and animal infections remain limited, particularly in high-risk pastoral communities. This study aimed to determine brucellosis seroprevalence and associated risk factors in humans and livestock in Nyagatare District, a major livestock-producing region of Rwanda.

METHODS

A cross-sectional study was conducted from March to October 2023 across three sectors (Karangazi, Rwempasha, and Rwimiyanga sectors) using stratified random sampling. Blood samples were collected from 886 humans and 930 livestock (637 cattle, 222 goats, 71 sheep) and screened via indirect Enzyme-Linked-Immunosorbent Assay. Risk factor data were collected through structured questionnaires. Multivariable logistic regression identified factors associated with seropositivity, with results expressed as odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

The overall seroprevalence was 19.9% (176/886; 95% CI: 17.3-22.6) in humans and 10.9% (101/930; 95% CI: 9.0-13.0) in livestock. Among livestock, seroprevalence was highest in cattle (11.9%, 76/637; 95% CI: 9.4-14.5), followed by goats (11.3%, 25/222; 95% CI: 7.1-15.4), and sheep (1.4%, 1/71; 95% CI: 0.0-4.2). In humans, significant risk factors included male gender (OR = 2.66, 95% CI: 1.57-4.64, p < 0.001), age >55 years (OR = 7.39, 95% CI: 3.82-14.8, p < 0.001), and working as an animal health practitioner (OR = 2.90, 95% CI: 1.38-6.06, p = 0.005). In livestock, key risk factors included retention of aborted animals in herds (OR = 10.0, 95% CI: 2.27-49.2, p = 0.003), improper disposal of aborted fetuses (OR = 3.15, 95% CI: 1.18-7.99, p = 0.018), and shared water sources (OR = 2.49, 95% CI: 1.27-4.93, p = 0.008). Geographic analysis revealed higher seropositivity in the Rwimiyaga sector (OR = 3.06, 95% CI: 1.37-7.45, p = 0.009).

CONCLUSIONS

This study reveals a high burden of brucellosis in both human and livestock populations in Nyagatare District, with particularly elevated risk among animal health workers and where livestock management practices are poor. Our findings suggest three targeted interventions: (1) Mandatory use of personal protective equipment for animal health workers, (2) Proper disposal of infectious animal materials, and (3) Sector-specific control strategies for high prevalence areas. These results provide critical evidence for developing One-Health interventions to control brucellosis in Rwanda and similar East Africa settings.