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Studies of caprine arthritis-encephalitis viruses, associated diseases and their control in Western Australia

Ellis, Trevor Maxwell (1986) Studies of caprine arthritis-encephalitis viruses, associated diseases and their control in Western Australia. PhD thesis, Murdoch University.

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Abstract

The clinical signs and pathology of chronic arthritis-synovitis and chronic interstitial pneumonia in goats in Western Australia were described.

Retroviruses were isolated by explant culture techniques from synovial membrane of joints with arthritis, lung tissue of goats with chronic interstitial pneumonia and lung tissue of goats with arthritis but no pneumonic lesions. Similar viruses were also recovered from peripheral blood leucocytes, alveolar macrophages and cells centrifuged from colostrum of goats with arthritis, or arthritis and chronic interstitial pneumonia, by co-cultivation of these cells with normal goat synovial membrane (GSM) cells.

The physico-chemical characteristics of the isolated retroviruses were similar to those previously reported for caprine arthritis encephalitis virus (CAEV) which was initially isolated from joint lesions of goats in the USA. These similarities included cultural and morphological characteristics, the presence of RNA-dependent DNA polymerase in the virion, a buoyant density of 1.15 g/ml, similarities in protein composition and antigenic relationship to maedi-visna virus. One property distinguishing the local virus isolates from those described in the USA was the mechanism of virus-induced cell fusion. CAEV-induced cell fusion was previously reported to require de novo synthesis of viral protein in infected cells. Local isolates of CAEV induced cell fusion of GSM cells before progeny virus was detected and de novo synthesis of virus coded proteins was not required.

The physico-chemical characteristics of CAEV isolates from lungs of goats with chronic interstitial pneumonia and joints of ii goats with chronic arthritis were indistinguishable. Inoculation of CAEV-free goats with viruses isolated from either type of lesion induced arthritis-synovitis lesions which were similar to those in goats with naturally-occurring disease. None of the isolates from either lung or joint tissue induced interstitial pneumonia in experimentally infected goats, although there was evidence which suggested that lungworms or other granuloma-inducing processes interacted with CAEV to produce chronic interstitial pneumonia.

Enzyme linked immunosorbent assays (ELISA), agarose gel immunodiffusion (AGIO) and serum neutralisation tests were developed to detect CAEV-antibody in goats. Goats with antibody to CAEV were persistently infected with CAEV. Serological surveys of goats in Western Australia indicated a high prevalence of infection in dairy goats and a low prevalence in Angora goats. There was no evidence of CAEV infection in feral goats.

All CAEV isolates shared common ELISA and AGIO antigens but antigenic heterogeneity was demonstrated using serum neutralisation tests. Antigenic variation of CAEV was shown to occur during persistent infection of goats although the significance of this variation in the pathogenesis of CAEV-induced lesions appeared to be minimal.

Ingestion of colostrum and milk from infected does was shown to be a major method of transmission of CAEV, although the virus was also transmitted between older goats during prolonged close contact or mating. This information was used to devise a programme which was successfully used to eradicate CAEV infection from a herd with a high prevalence of CAEV infection.

Item Type: Thesis (PhD)
Murdoch Affiliation: School of Veterinary Studies
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: repository@murdoch.edu.au. Thank you.
Supervisor(s): Robinson, Wayne and Wilcox, Graham
URI: http://researchrepository.murdoch.edu.au/id/eprint/53421
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