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.
ABSTRACT
BACKGROUND AND AIM: African horse sickness (AHS) is a non-contagious viral disease of horses and other equids caused by an arbovirus belonging to the Reoviridae family and genus Orbivirus. AHS is an endemic disease that is responsible for the death of a high number of horses every year in Namibia. At present, there is no information on the prevalence and distribution of AHS virus (AHSV) serotypes in the different regions of Namibia. Therefore, this survey aimed to fill this knowledge gap by investigating the AHSV seroprevalence in Namibian donkeys. MATERIALS AND METHODS: A total of 260 blood samples (20 samples for each region) were randomly collected from donkeys aged between 3 and 5 years. Sera were screened for AHSV-specific immunoglobulin G antibodies using acommercial competitive enzyme-linked immunosorbent assay kit and samples positive to AHSV antibodies were further tested by serum neutralization (SN) assay to evaluate the AHSV serotype-specific immune response. RESULTS: Seroprevalence of antibodies against AHSV in Namibian donkeys was 63.5%. The AHSV prevalence was significantly higher in the northern region (64%) than in the southern region (36%). A significantly (p<0.05) higher number of donkeys had antibodies against AHSV-6 (37.8%) and AHSV-9 (37.8%). The AHSV-2, AHSV-6, and AHSV-9 prevalence were higher (p<0.05) in the northern regions compared to the southern regions. None of the donkeys in this study, however, tested positive for AHSV-8. CONCLUSION: Results of the current study indicate that all AHSV serotypes have either circulated previously or are circulating in Namibia except for AHSV-8. In particular, AHSV-1, -2, -3, -4, -5, -6, and -9 serotypes have circulated or are circulating in the northern region of Namibia, while AHSV-1, -4, -5, -6, -7, and -9 have infected donkeys in the south. AHSV-9 and AHSV-6 were the most prevalent serotypes detected in donkeys in this study. SN results showed that several donkeys from Kavango East, Kavango West, and Ohangwena regions had been exposed to multiple serotypes, indicating the possibility of cocirculation of several strains in Namibia.
ABSTRACT
In January 2019, high mortalities were reported among African Penguins (Spheniscus demersus) in a breeding colony on Halifax Island, Namibia, Africa. Analysis of samples by reverse transcription quantitative PCR indicated the presence of highly pathogenic avian influenza (HPAI) subtype H5N8. Sequence analysis of the hemagglutinin and neuraminidase genes confirmed the presence of the virus in the birds and its high similarity to HPAI subtype H5N8 identified in South Africa in 2017. There have been no previous reports of HPAI H5N8 in Namibia.
