Soft plastron, soft carapace with skeletal abnormality in juvenile tortoises: Histopathology and isolation of a novel Picornavirus from Testudo graeca and Geochelone elegans

摘要

Objective: A disease is described in juvenile tortoises (Testudo graeca and Geochelone elegans) consisting mainly of a soft carapace, soft plastron and deformed skeleton. The aim of this study was to determine histopathological lesions and the biological properties of the isolated viruses. Materials and methods: Clinical signs and gross pathology were determined on diseased and healthy appearing tortoises. Paraffin sections were stained with HE, PAS and Prussian Blue and histologically examined. Terrapene heart (TH-1) cell cultures served for virus isolations from 64 tissues and 104 swabs. One isolate (isolate 1243/37 tongue) was used in neutralization tests on 19 sera. Results: Retarded growth and increasingly soft plastron and carapace were the prominent signs in diseased tortoises. Pathological lesions consisted of dilated urinary sac, enlarged kidneys and livers. Histo-pathologically, hepatic hemosiderosis, hypoplastic anaemia, congestive glomerulonephrosis and osteodystrophy were seen. A novelvirus ("virus X") was isolated from 64 organs and 79 of 104 swabs. The isolated viruses were identified as a novel chelonid Picornavirus based on cytopathic effect, resistance to chloroform and stability at low pH. Co-cultivation with 5-iodo-2'-deoxyuridine and actinomycin D did not reduce virus titres. Electron microscopically, round, non-enveloped particles (25-30 nm) were detected. Neutralizing antibodies to the isolate 1243/37tongue were present in 17 of 19 sera from seven species of tortoises. Conclusion and clinical relevance: Nephropathy, osteodystrophy and virus isolations suggest a viral aetiology. Metabolic bone disease is the major differential diagnosis. Further investigations in vivo are needed to evaluate the likely effects of the Picornavirus on tortoises.