The significance of viral, bacterial and protozoan infections in zebra : a systematic review and meta-analysis of prevalence

Wild equids can harbour multi-host infectious agents that are able to affect other wildlife species, but also domestic animals and humans. The direct and indirect contact between wild and domestic equids is constantly increasing due to global movement of horses and equine products, the depletion of natural areas and climate and land-usage changes, which could result in burdensome epidemics. Nevertheless, currently there is a lack of adequate epidemiological data from zebra. Three electronic databases were searched from 10 to 20 March 2021 for publications reporting bacterial, viral and protozoan infections in zebra. Data for a total of 12 relevant variables were extracted from reviewed papers to undergo a qualitative analysis. Prevalence-reporting studies were subjected to meta-analysis for estimating the pooled prevalence and seroprevalence of microbials in wild zebra populations. We identified 30 pathogen species and the most represented were equine Herpesvirus 1 and 9, Bacillus anthracis, African horse sickness virus and Theileria equi. They were reported from all the three zebra species, both in captivity and wilderness. Pooled seroprevalences were estimated for the equine Orbiviruses AHSV (70%; 95% CI: 35–96%) and EEV (21%; 95% CI: 8–38%) and for the equine α-Herpesviruses EHV-1 (72%; 95% CI: 43–93%), EHV-4 (40%; 95% CI: 0–100%) and EHV-9 (58%; 95% CI: 9-98%), and pooled prevalences for the equine piroplasms T. equi (100%; 95% CI: 94–100%) and B. caballi (8%; 95% CI: 0–28%). Zebra is most probably a component of the reservoir from which AHSV, EHV-1 and T. equi can be directly or indirectly transmitted to horse populations, potentially causing disastrous epidemics. Zebra can also harbour zoonotic pathogens like B. anthracis, Brucella spp., A. phagocytophylum, CCHFV and T. brucei. Other agents like EHV-9, BPV-1 and BPV-2 have the potential to spread from zebra to other wild endangered animal species. We conclude that zebra is an important host of multiple and dangerous pathogens for both animals and humans. Comprehensive studies focused on the prevalence of infectious agents present in zebra populations and the associated risk factors are required.