Re-emergence of fibromatosis in farmed game hares (Lepus europaeus) in Italy

Fibromatosis in hares has not been reported in Northern Italy since 1961 (Leinati and others 1961). After 40 years, in the same geographic area an outbreak of fibromatosis in reared game hares occurred. Two hundred and fifty (25%) of animals examined showed typical skin lesions with no difference in prevalence related to the age. Skin tumours of 1 to 3 cm in diameter were present on the legs and ears. After 4-6 weeks the skin lesions disappeared and the animals spontaneously recovered. Histologically many large cells with large nuclei and numerous periodic acid-Schiff inclusion bodies in their abundant cytoplasm were observed. Electron microscopy confirmed the presence of poxviruses. The virus produced typical pocks on the chorion-allantoic membrane of SPF embrionated chicken eggs, but no cytopathic effect on a continous line of rabbit kidney cells (RK13). Cross-infection trials and serological examinations of challenged rabbits, hares and cottontails were carried out but none of the animals developed the disease and none of the sera examined contained antibodies against myxoma virus.