Effectiveness of the Shope Papilloma Virus in Various American Rabbits

Abstract

The virus causing cutaneous horns and papillomas in western cottontail rabbits (Sylvilagus floridanus, Allen) gives rise to vigorous growths of the same sort in domestic rabbits (Genus, Oryctolagus). In animals of both kinds these growths have the immediate character of neoplasms, and in domestic rabbits they frequently progress to cancer. For this reason, the biological range of effectiveness of the virus has a special interest. Thus far rabbits only have proved susceptible to the virus. A Kansas dealer supplying cottontails with “natural” papillomas states that he has never seen them in any of thousands of jack-rabbits (Lepus californicus, Gray); yet in one of 24 he sent us a small but typical growth existed, hidden by the fur. Three mixtures were made of the host's blood serum with various proportions of glycerinated cottontail papilloma extract, and after incubation all were rubbed into the scarified skin of each of 3 domestic rabbits, which received also similar mixtures made with the sera of 4 other jack rabbits of the same lot. Growths developed at every site except where the mixtures with serum from the papillomatous animal had been inoculated. The “natural” jack rabbit papilloma enlarged slowly for some weeks, when the animal died and it was removed to 50% glycerine. An extract made 36 days later and inoculated into scarified domestic, cottontail, jack and snowshoe rabbits (Lepus americanus, Erxleben), 3 of each, produced growths in all. They were indistinguishable from such as are caused by cottontail virus. In 2 further experiments 2 jack rabbits were inoculated with cottontail virus extracts of differing derivations. Growths appeared in 3 of the 4 animals, the fourth dying too soon to be deemed resistant. An extract of the glycerinated papillomatous tissue from 1 of the others gave rise to growths in 2 of 3 domestic rabbits and in 2 jack rabbits.