Abstract
BACKGROUND AND AIM: Epizootic hemorrhagic disease virus (EHDV), an Orbivirus transmitted by Culicoides midges, infects a wide range of ruminant species including dromedary camels (Camelus dromedarius). Although circulation of EHDV has been documented in cattle in the Sultanate of Oman, its epidemiology in camels remains poorly characterized. This study was conducted in the Al Batinah North and Al Batinah South governorates, coastal regions with hot, arid climates favorable to vector activity, to estimate individual-level seroprevalence of EHDV antibodies in dromedary camels, identify associated risk factors using univariate and multivariate analyses, and evaluate spatial distribution patterns to inform future control measures in multi-host livestock systems. MATERIALS AND METHODS: A cross-sectional study was performed between September 2020 and July 2021. Serum samples were collected from 415 camels across 50 holdings using convenience sampling. Antibodies against EHDV were detected with a commercial competitive enzyme-linked immunosorbent assay (c-ELISA) targeting the VP7 protein (sensitivity = 85.9 %, specificity = 99.7 %). True prevalence (TP) was calculated using the Rogan-Gladen estimator. Univariate associations were assessed with chi-square or Fisher's exact tests; variables with p < 0.25 were entered into backward stepwise binary logistic regression. Spatial analyses included average nearest-neighbour clustering, Getis-Ord Gi* hot-spot analysis, and kernel density estimation in ArcGIS. RESULTS: Apparent seroprevalence was 40.2 % (95 % confidence interval [CI]: 35.5-45.1 %), with an estimated TP of 46.7 % (95 % CI: 41.3-52.3 %). No significant difference existed between governorates (p = 0.520). In univariate analysis, seropositivity was significantly higher in camels > 4 years of age (45.9 % vs 19.3 %; p < 0.001), in breeding/leisure camels (43.1 % vs 20.8 %; p = 0.002), and in animals kept in contact with other ruminants (49.3 % vs 35.6 %; p = 0.007). After multivariate adjustment, only age > 4 years (odds ratio [OR] = 3.4, 95 % CI: 1.88-5.96; p < 0.01) and contact with other ruminants (OR = 1.6, 95 % CI: 1.05-2.44; p = 0.029) remained independent risk factors. Global spatial clustering of positive holdings was highly significant (nearest-neighbour ratio = 0.39, z = -8.26, p < 0.001), with elevated density along coastal agricultural corridors. CONCLUSION: This first large-scale serological survey confirms active circulation of EHDV among dromedary camels in northern Oman. Older age and mixed-species herding are the main risk factors identified. The findings highlight the importance of camels in the multi-host ecology of EHDV and emphasize the need for integrated national surveillance, vector studies, and molecular characterization of circulating serotypes to support evidence-based control strategies in a changing climate.