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

Jean Bosco Ntivuguruzwa¹Emmanuel Kabalisa²Happy Jean Bosco Asifiwe³Adeline Gapasi Uwamahoro⁴Immaculée Nyampinga²Agrippine Mukarurangwa²Nadine Rujeni³Jean Paul Habimana¹Marie Louise Mukamuhirwa¹Patience Karemera¹Placidie Umukunzi¹Beathe Iradukunda¹Patrick Mazimpaka¹Peter Hudson^5,6Maurice Byukusenge⁷Joram Josephat Buza⁸Vivek Kapur^5,8,9Adolphe A Ndikubwimana⁴Isabelle Mukagatare²Martin Ntawubizi¹Robab Katani^10,8*

• ¹School of Veterinary Medicine, College of Agriculture, Animal Sciences and Veterinary Medicine, University of Rwanda, Nyagatare, Rwanda
• ²National Reference Laboratory, Rwanda Biomedical Center, Kigali, Rwanda
• ³School of Health Sciences, College of Medicine and Health Sciences, University of Rwanda, Kigali, Rwanda
• ⁴School of Public Health, College of Medicine and Health Sciences, University of Rwanda, Nyagatare, Rwanda
• ⁵The Pennsylvania State University Huck Institutes of the Life Sciences, University Park, United States
• ⁶The Pennsylvania State University Department of Biology, University Park, United States
• ⁷The Pennsylvania State University Department of Veterinary and Biomedical Sciences, University Park, United States
• ⁸Nelson Mandela African Institute of Science and Technology Water Infrastructure and Sustainable Energy Futures, Arusha, Tanzania
• ⁹The Pennsylvania State University Department of Animal Science, University Park, United States
• ¹⁰The Pennsylvania State University (PSU), University Park, United States

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.