Abstract
Summary
Intradermal injection of 320 domestic rabbit infectious doses of Shope's fibroma virus caused mortality in cottontail rabbits (Sylvilagus floridanus) infected at 6 days of age or younger. Cottontails infected at 14 days of age or younger developed immense primary tumors at the site of inoculation. Fatal cases were observed to have foci of tumor cells in the kidneys and occasionally in the liver and spleen. The virus could be isolated from fatally infected animals from kidney, spleen, liver, lung, brain, and tumor tissues. The same dose of virus given by the same route to domestic rabbits (Oryctolagus cuniculus) of the same ages produced a more acute, more rapidly fatal and much less proliferative disease. The possible ecological significance of these observations is discussed and contrasted with effects of the closely related myxoma virus.
I am grateful to Mr. Orrin Rongstad for help in procurement of cottontail rabbits. The counsel of Drs. G. M. ZuRhein and S H. McNutt in the histopathological aspects of this study is gratefully acknowledged.
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