Clinical and epidemiological investigations of Orbivirus infections in domestic dogs (Canis lupus familiaris)

Abstract

Dogs are atypical host species for some of the most economically important orbiviral diseases, African horse sickness (AHS) and bluetongue (BT). Dogs are the only non-equid species to develop the severe fatal form of AHS, and along with the Eurasian lynx, dogs are the only non-ruminants to develop fatal bluetongue (BT). However, the role of dogs as a host species for orbiviruses has been largely dismissed as incidental or of low significance in the epidemiology of orbiviruses. In light of recent dog mortalities due to AHS which occurred with suspected midge-borne transmission, this thesis examines clinical and epidemiological features of Orbivirus diseases in South African dogs. The author shows that exposure to the African horse sickness virus (AHSV) in dogs in Tshwane, South Africa was common and frequent, with as many dogs estimated to have been exposed to AHSV as the population of horses in the area. At the onset of this investigation, only AHS had been described in South African dogs. The author describes the novel identification of the bluetongue virus (BTV) and possible equine encephalosis virus in South African dogs. The author describes the clinical presentation and management of a pregnant dog diagnosed with naturally occurring BT. The author investigates the farm of origin for this dog and shows a high level of exposure to BTV in dogs on the farm was high and detected the viral RNA from blood samples in three dogs (50%). The author reports the detection of equine encephalosis from samples collected from a puppy with a fatal respiratory disease. The findings of this study suggest dogs could play a greater role in the persistence, spread and introduction of orbiviruses than previously thought.