Abstract
This is the first case of African horse sickness (AHS) in a dog where there was no apparent ingestion of horse meat. Significantly, the dog was part of a colony that resides in a Good Clinical Practice and Good Laboratory Practice accredited facility where complete history, weather and feeding records are maintained. The dog died after a week-long illness despite therapy. The principal post-mortem findings were severe hydrothorax and pulmonary consolidation (red hepatisation of the lungs). Histopathology revealed severe oedema and congestion of the lungs, hyaline degeneration of the myocardium and congestion of the liver sinusoids. Immunohistochemistry detected AHS-positive staining granules in the myocardium, whilst a real-time reverse transcription quantitative Polymerase chain reaction assay of tissue samples was strongly positive for African horse sickness virus nucleic acid. Other dogs on the property showed a 43%seroconversion rate to AHS.
Highlights
African horse sickness (AHS) is caused by African horse sickness virus (AHSV), a virus in the family Reoviridae, genus Orbivirus, of which there are nine known serotypes (Coetzer & Guthrie 2004)
It has been proposed that AHS is endemic to the eastern parts of the Mpumalanga and Limpopo provinces, where the virus is maintained in zebra reservoirs and from where its spreads southwards during the summer months (Bosman, Brückner & Faul 1995)
As none of the whole blood samples in the dog colony were positive for AHSV by real-time RTPCR, this could indicate that the infection in indirect enzyme-linked immunosorbent assay (iELISA)-positive animals occurred more than four months prior to sample collection, that AHSV is not bound to canine red blood cells to the extent that bluetongue virus is bound to red blood cells (Hassan & Roy 1999; Weyer et al 2013) or that the dogs were sub clinically infected more than 40 days previously, as sub clinically-infected horses only have detectible RNA levels over this period in whole blood (Weyer et al 2013)
Summary
African horse sickness (AHS) is caused by African horse sickness virus (AHSV), a virus in the family Reoviridae, genus Orbivirus, of which there are nine known serotypes (Coetzer & Guthrie 2004). Notwithstanding the controversy, it is clear that Culicoides spp. do not feed on dogs to the extent that they feed on horses and livestock, it is possible that dogs could be an incidental host for the midges Other potential vectors such as mosquitos and ticks (e.g. Rhipicephalus sanguineus) have been suggested and in some cases shown to be capable of transmitting AHS, the epidemiological importance of this is not known (Alexander et al 1995; Mellor 1993). Macropathological lesions tend to correspond to the ‘dunkop’ form of the disease in horses, including: severe oedema and hepatisation of the lungs; hydrothorax; petechiation on the pleura; inflammation and congestion of the gastric and intestinal mucosa; blood-stained faeces and enlarged spleen and liver.
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