Bovine coronavirus presence in domestic bovine and antelopes sub-Saharan Africa: evidence from Namibia

Background: Bovine coronavirus (BoCV) causes significant economic losses to cattle farming due to mortality in calves, reduced growth performances and milk production in feedlots and dairy cattle. Worldwide distribution of BoCV has been demonstrated, although knowledge of its epidemiology in Africa, especially in the sub-Saharan region, is limited. Results: In the present study, a total of 208 swab samples of wild ruminants and 435 bovines from different regions of Namibia were obtained and tested by a BoCV-specific qRT-PCR. Twenty-six bovine samples tested positive [26/435 (5.98%; 95CI: 3.94-8.64%)] while, among the wild ruminants, only Greater Kudu (Tragelaphus strepsiceros) were shown to be positive [13/52 (25.00%; 95CI: 14.03-38.95%)] of which 8 showed clinical signs. Analysis of partial nucleoprotein and spike protein gene sequences and comparison with international reference sequences demonstrated the existence of a unique Namibian clade, resulting from a single introduction event around 2010 followed by local evolution. Although the introduction source remains unknown, contact between bovine and wild animals appears likely. Conclusions: The present study represents the first report of BoCV circulation in southern Africa, which showed a relatively high frequency and the ability of persisting and evolving locally in the absence of further foreign introductions. The implications for disease spread among domestic bovines and the potential impact on wildlife should encourage broader investigations on BoCV involving other African countries. Moreover, the Greater Kudu’s susceptibility to BoCV infection was also proven, further highlighting the host plasticity of this virus.