Seroprevalence of African horse sickness in selected donkey populations in Namibia

Abstract

<jats:p>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 a commercial 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&lt;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&lt;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.</jats:p>

West Nile Virus Seroprevalence in a Selected Donkey Population of Namibia

“…Differently from African horse sickness, no overall differences were observed between the northern and southern part of the country (21). Potentially, the different vector ecology and distribution could explain the observed difference.…”

“…Although, cases of West Nile fever were never recorded in equids around Namibia, the results of this study provided enough evidence about the presence and viral circulation all around the country, testifying the practical usefulness end efficacy of routinary serological monitoring of donkeys as sentinels for WNV presence. Surveillance systems based on virus detection in birds, mosquitoes, horses and poultry are used in several countries to estimate the public health risk for flaviviruses such as WNV (21). A livestock census conducted in Namibia in 2015 showed a population of 27.151 horses and 148.859 donkeys (22).…”

Epidemiological aspects of some equine viral diseases

“…In Gambia, 96% of the tested horses and donkeys were seropositive for AHS serotype 9 (37). All AHSV serotypes are circulating in Namibia, and Zimbabwe except for AHSV-8 with the AHSV-9 and AHSV-6 were the most prevalent serotypes detected in donkeys (38). A recent outbreak was reported in Thailand with afraid of being a threat to other Asian countries as sometimes the virus jumps out of endemic regions and spread far away as India and Pakistan (39) (Figure 4).…”

Serological Examinations of Significant Viral Infections in Domestic Donkeys at the Special Nature Reserve “Zasavica”, Serbia

“…African horse sickness is currently limited to the Sub-Saharan region where it is responsible for deaths of horses every year [ 20 ]. However, several enzootics in the 1959–1965 period were also recorded outside of the African region, in Asia and in North Africa.…”