Abstract:
Commingling of horses from various populations, together with physiological stress
associated with transport and confinement at a sales complex, may be associated with
detection and transmission of equine herpesvirus type-1 (EHV-1) and -4 (EHV-4). This
prospective cohort study aimed to investigate the currently undefined prevalence of EHV-1
and -4 in young Thoroughbreds at an auction sale in South Africa, and associations between
clinical signs, physiological stress and viral detection.
Ninety, two-year old Thoroughbreds (51 colts, 39 fillies) were consigned from eight farms and
sampled at a South African auction sale. The horses were monitored for pyrexia and nasal
discharge. Nasal swabs were collected for quantitative polymerase chain reaction (qPCR)
assay to detect EHV-1 and -4 and faecal samples were collected for enzyme immunoassay
(EIA) to determine faecal glucocorticoid metabolite (FGM) concentrations.
EHV-4 nucleic acid was detected in some and EHV-1 nucleic acid in none of the population.
Pyrexia and nasal discharge were poor indicators of EHV-4 status. Variation in FGM
concentrations was best explained by transportation and preparation for auction. Peaks in
EHV-4 detection and increases in FGM concentrations were identified shortly post-arrival
and on the first day of auction. Temporal changes in FGM concentrations of horses from
individual farms showed two distinct patterns: Pattern A (biphasic peaks) and Pattern B
(single peak).
It was concluded that sales consignment was associated with some EHV-4 nucleic acid
detection and distinctive physiological stress patterns in this population of young
Thoroughbreds.
