Evidence of African horse sickness virus infection of Equus zebra hartmannae in the south-western Khomas Region, Namibia.

This study explores the occurrence of African horse sickness virus (AHSV) in Hartmann’s mountain zebra, a suspect, yet unproven, reservoir host of the virus, in Namibia’s Khomas Region. The research was conducted following reports of equine deaths from suspected AHSV in an area previously thought to be locally AHSV-free.

Background

• In 2008, cases suspected to be African horse sickness (AHS) were reported from the arid Khomas Region of Namibia, an area initially believed to be free of AHS.
• Hartmann’s mountain zebra (Equus zebra hartmannae) occurs in this region and is an unconfirmed potential reservoir host of the African horse sickness virus.

Methodology

• In order to verify the presence of the AHSV and/or antibodies against this virus in the zebras, tissue samples, serum, and blood from 31 culled E. z. hartmannae were analysed.
• Examination of the samples was executed through reverse transcription-polymerase chain reaction (RT-PCR), a common method used in molecular biology to detect specific genetic material in samples, and enzyme-connected immunosorbent assay (ELISA), a standard test for measuring immunological agents in specimens.

Findings

• AHSV antibodies were detected in all 18 samples that were tested implying that these zebras have been exposed to the virus and produced an immune response.
• In addition to antibodies, active AHSV double-stranded RNA was detected in 26% of the zebras, confirming that these zebras are not only exposed to but are also exploiting the virus.
• These findings provide the first concrete evidence that Hartmann’s mountain zebra can indeed become infected with the African horse sickness virus.