Abstract
Thoroughbred foal body temperature data were collected from shortly after birth until shortly after weaning during the 2007/2008 season on a stud farm in the Western Cape Province of South Africa. Equine encephalosis (EE) caused by EE virus (EEV) serotype 4 (EEV-4) occurred in the foal group during the first autumn after their birth (March and April 2008). A descriptive study was undertaken to provide data on the EEV maternal antibody status, the association between pyrexia and EEV infection, and the incidence of infection amongst the foals prior to and during the episode. This included the frequent capturing of foal body temperature data and regular collection of serum and whole blood during pyretic episodes. Infection by EEV was determined using both virological and serological methods. A high EE incidence of at least 94% occurred amongst the foal cohort, despite the fact that 37% of foals had previously shown maternal antibody to EEV-4. Pyrexia in foals was not directly associated with EE infection and 41% of infected foals showed no detectable pyretic episode. Information obtained from this EE episode showed the high incidence of EEV infection in foals during the first autumn after their birth. Monitoring foal body temperature can alert farmers to outbreaks of infectious disease, such as EE. These results are relevant to the epidemiology of EE and facilitate greater understanding of it as a differential diagnosis of African horse sickness (AHS), given that EE and AHS have similar epidemiologic profiles.
Highlights
Equine encephalosis (EE) is an arboviral disease of equids that is transmitted by Culicoides midges (Paweska & Venter 2004)
Whilst there have been prior studies on the seroprevalence of EE virus (EEV) infection of horses in South Africa, this study provides data on the EEV maternal antibody status, the association between pyrexia and EEV infection, and the incidence of infection amongst Thoroughbred foals prior to and during a natural infection with EEV
Between January and March 2008, prior to the outbreak of EE, 34/93 (37%) foals had detectable levels of serum http://www.ojvr.org neutralisation test (SNT) antibodies to EEV-4, the titres of which were waning as foals aged (Figure 1)
Summary
Equine encephalosis (EE) is an arboviral disease of equids that is transmitted by Culicoides midges (Paweska & Venter 2004). The causative agent of EE is EE virus (EEV), a member of the Orbivirus genus in the Reoviridae family. EEV infections of horses are typically unapparent or manifest as only a mild or subclinical disease (Crafford et al 2011). The clinical signs may be similar to those seen in cases of African horse sickness (AHS), which is caused by the closely related AHS virus (AHSV) that is transmitted by haematophagous Culicoides midges (Howell, Guthrie & Coetzer 2004). The viraemic period in EEV-infected horses is generally brief, and horses do not act as long-term carriers of the virus (Erasmus et al 1970). The mortality rate of EE is less than 5% (Howell et al 2004)
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call