Abstract
West Nile Virus (WNV) is a mosquito-borne virus enzootically maintained in birds. However, it can incidentally infect other species, leading to sometimes severe clinical consequences like in horses and especially human beings. Despite the topic relevance, the presence and distribution of WNV are currently unknown in Namibia. Several countries implement surveillance systems based on virus detection in birds, mosquitoes, and vertebrate species including horses. The present study aimed to fill this knowledge gap by serologically evaluating WNV exposure in Namibian donkeys, whose population is remarkably bigger than the horse one. Forty-seven out of 260 sampled animals showed neutralizing antibodies against WNV (18.07% [95% CI = 13.59–23.30%]), demonstrating its circulation in all country territory, although, with apparent regional differences. On the contrary, no association with animal age or sex could be identified. The present study demonstrates the widespread presence of WNV in Namibia as well as the practical utility and effectiveness of donkeys as sentinels for infection surveillance. Due to clinical relevance, vaccination campaigns should be considered for horses of high economic or genetic value. Additionally, the burden of WNV infection on human health should be carefully evaluated.
Highlights
West Nile Virus (WNV) is a mosquito-borne virus of the genus Flavivirus within the family Flaviviridae
A total of 108 out of 260 (41.54% [95% CI = 35.38–47.79%]) analyzed donkeys tested positive by ELISA, and in 47 out of 260 (18.07% [95% CI = 13.59–23.30%]) the presence of WNV neutralizing antibodies was confirmed by virus neutralization test (VNT) (Table 1)
One hundred and eight out of 260 samples (41.54% [95% CI = 35.38–47.79%]) tested positive using a competitive ELISA test, only 47 (18.07% [95% CI = 13.59–23.30%]) were confirmed by the reference WNV VNT
Summary
West Nile Virus (WNV) is a mosquito-borne virus of the genus Flavivirus within the family Flaviviridae. First discovered in 1937 in the West Nile district, Uganda [1], WNV is maintained in nature in an enzootic cycle involving ornithophilic mosquitoes and birds. Birds act as reservoirs and amplifying host while mosquitoes as vectors [2]. Humans and horses are incidental or deadend hosts. Only ∼10% of infected horses develop clinical signs [4] and the mortality can reach 50% [4]. The susceptibility of other equine species to WNV infection remains poorly documented. WNV antibodies have been found in donkeys and mules in several African countries [5,6,7,8].
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