124
46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
The effect of sales consignment on
the nasal shedding of EHV-1 and -4
in young Thoroughbred horses
Badenhorst, Ma, Ganswindt, Ab, Page, Pa, Guthrie, AJ c and Schulman, ML d*
a
d
Companion Animal Clinical Studies, bDepartment of Anatomy and Physiology, cEquine Research Centre and
Section of Reproduction, University of Pretoria
Introduction
Equine respiratory infection is a major cause of disease and economic loss and
negatively impacts on animal welfare worldwide. Anecdotal evidence suggests that up
to 50% of veterinary call-outs made to horses in racing are for respiratory disease.
Among the most common pathogens recognised in cases of infectious upper
respiratory tract disease (IURD), are equine herpesvirus-1 and -4 (EHV-1 and -4),
equine influenza virus (EIV) and Streptococcus equi subspecies equi. In young horses,
infection is often associated with an outbreak of acute respiratory disease
characterised by biphasic-pyrexia (rectal temperature > 38.5 ˚C) and serous nasal
discharge that may later become mucopurulent. Mild or sub-clinical infections are
common.
Sales events provide an opportune environment for commingling of horses
originating from various populations. This factor, together with the stress associated
with transport to, and confinement at the sale yards, predispose these horses to
shedding and transmission of contagious respiratory pathogens. Young horses are
more susceptible to infectious respiratory pathogens, with a higher detection rate
for these pathogens being observed during the winter months. The identification of
risk factors for shedding and transmission of pathogens associated with sales events,
will contribute towards improved management of horses consigned to such events.
EHV-1 and -4 are closely related alpha herpesviruses and are considered ubiquitous
in equine populations worldwide. Key aspects in the pathogenesis of EHV-1 and -4
are latency and stress-related recrudescence. Respiratory tract replication and
shedding in respiratory secretions has been associated with stressors such as long
distance transport, overcrowding, commingling, participation at show events, sales,
hospitalisation and immunosuppression due to illness or immunomodulatory drugs.
Horizontal spread to naive animals may occur by means of direct horse-to-horse
contact, inhalation of aerosolised virus or contact with fomites contaminated by
respiratory secretions. Viral nucleic acid (DNA) can be detected in nasal secretions
by means of qPCR during the period of viral shedding, on average a duration of 14 d
post-infection.
Confirmation of prevalence of infection and identification of factors that determine
the risk of inf V7F