Brucellosis seroprevalence in captive scimitar-horned oryx (Oryx dammah) in the United Arab Emirates and associated risk factors

Abstract

The scimitar-horned oryx ( Oryx dammah ) (SHO) is a large African antelope that became extinct in the wild just over two decades ago. Conservation of the species is of prime importance, but it might face pathogen stressors. Brucella melitensis biovar 1 was previously confirmed in a high-density captive population of SHO held in Abu-Dhabi emirate. The infection reached 67.0% (95% CI: 64.0 - 70.0) individual seroprevalence (n=959) during testing performed between January 2013 and January 2015. A model based on a multivariable logistic regression analysis showed that the seroprevalence ranged from 51.2 (95% CI: 39.6 - 62.7) to 86.9% (95% CI: 82.4 - 91.4) between six different enclosures, and probability of being seropositive was 1.83 (95% CI: 1.32 - 2.55) higher in females than in males, 3.09 (95% CI: 1.66 - 5.91) and 9.35 (95% CI: 4.66 - 19.44) higher in subadults and adults than in juveniles, respectively. The three serological tests used in this study (Rose Bengal Test, lateral flow assay and in-house i-ELISA) had a perfect or near-perfect agreement (Cohen’s Kappa coefficient >=0.97). Recurrent high seroprevalence in time and congruence of results from three different serological tests point toward a persistent B.melitensis infection in a high-density captive SHO population. Conclusion and significance Testing strategy (Bengal Test, lateral flow assay or in-house i-ELISA) has no effect on the estimation of the brucellosis seroprevalence in SHO permitting the selection of a practical test. We call for an evidence-based control program, and Brucella vaccine efficacy and innocuity studies in this endangered species.