Spatial distribution and risk factors associated with ruminant brucellosis in different agroecological zones of Uganda

Brucellosis is a serious zoonotic disease with devastating impacts on public health and animal productivity. Despite an increasing number of reported cases in humans, livestock and wild animals, in Uganda no systematic countrywide research has been conducted to map the disease. A cross-sectional study was performed to estimate the seroprevalence in domestic ruminants in districts distributed in six agroecological zones. A total of 231 herds were sampled, and serum samples from 3536 bovine, 1691 caprine and 259 ovine tested with Rose Bengal Plate test. Metadata on the associated risk factors were collected via a structured questionnaire. Bivariable data analysis and Binary logistic regression model were used to determine the relationships between prevalence and risk factors at the herd level, while a Generalized Linear Mixed Model was applied at the individual animal level. Individual animal seroprevalence varied highly; Kasese 13.8% (confidence interval [CI 95%]: 11.26–16.73%), Wakiso 13.2% ([CI 95%]: 10.09–17.23%) and Apac 12.8% ([CI 95%]: 9.43–17.02%) districts presented the highest rates for bovine brucellosis, with no positive reactors in Lira and Masaka districts. The rest of the districts fell in between. Individual prevalence of caprine brucellosis equally varied, with Kiruhura district posting 26.4% ([CI 95%]: 19.87–34.13%), Kasese district 12.8% ([CI 95%]: 8.72–18.54%), and several districts posting 0%. Ovine brucellosis prevalence was insignificantly low. There was significant ( P < 0.001) variation in collective/herd brucellosis prevalence among the districts and agroecological zones. Kasese and Apac had the highest bovine herd prevalence (84.6%, [CI 95%]: 57.77–95.68%) and (55.6% [CI 95%]: 33.72–75.44%), respectively. Caprine brucellosis collective prevalence also varied, with Kasese district having the highest prevalence (85.7% [CI 95%]: 48.68–97.43%), followed by Kiruhura (66.7%, [CI 95%]: 30.0–90.32%). Agroecological zones with large herds, containing mixed breeds (P = < 0.001), that are freely interacting ( P = 0.001), sharing water resources ( P = 0.015), and frequent introductions of new livestock, were very vulnerable to introduction and spread of brucellosis. This study revealed a heterogeneous occurrence and distribution of domestic ruminant brucellosis, data which will be pivotal for implementing region specific control programs.