Abstract:
Equid alphaherpesvirus 1 (EHV-1) is an economically important virus, associated with
respiratory infection, late gestation abortion, neonatal death and myeloencephalopathy in
horses. The aim of the present study was to test the hypothesis that EHV-1 is present in the
nasopharynx and placentae of neonatal foals in the absence of clinical signs of infection. This
would suggest that vertical transmission of virus occurs in inter-epizootic periods: such
information could inform foaling management and the potential eradication of the virus by
vaccination.
Samples were collected from animals resident on a single farm in the Western Cape Province,
South Africa, which had not experienced a clinical outbreak of EHV-1 recently. Sterile swab
samples from 71 post-partum Thoroughbred mares, their healthy full-term foals and fetal
membranes were obtained and assayed for EHV-1 and EHV-4 nucleic acid using a duplex
quantitative polymerase chain reaction (qPCR).
The null hypothesis for this study was that EHV-1 was not present in the nasopharynx and
placentae of new-born, viable and healthy foals. As no EHV-1 or EHV-4 nucleic acid was
detected on a duplex EHV-1/EHV-4 qPCR assay from the mare and foal nasal and fetal
membrane swabs, the null hypothesis was accepted. It was therefore concluded that there
was no detectable EHV-1 and -4 DNA in this population at the time of sampling. It was
speculated that this may have been due to the cyclical nature of EHV-1 infections. The
inclusion of additional breeding seasons on additional farms would be valuable for future
studies.
