Carcinoma in the Cottontail Rabbit Following Spontaneous Virus Papilloma (Shope)

The Shope rabbit papilloma is an epithelial new growth caused by a filtrable virus and transmissible in series through cottontail (Genus, Sylvilagus) and domestic rabbits (Genus, Oryctolagus). Both in the gross and histologically it is similar to the virus papillomata of man, cattle and dogs., - Further, it has been found to possess not only the immediate characters of a tumor, but also the potentiality of progressive alteration until finally it may assume the characteristics of a squamous cell carcinoma with metastases., We have confirmed these findings. Carcinomatous changes have been reported previously only in experimentally inoculated domestic rabbits., , It would be highly significant were the host-parasite relationship so perfected in the natural host, the cottontail rabbit, that malignant changes never occurred. The significance of such a finding would apply irrespective of whether the virus per se, or whether secondary factors were responsible for the carcinoma. The purpose of this communication is to report that such is not the case, for we have observed carcinomatous degeneration of a naturally occurring papilloma in a wild cottontail rabbit. Of 132 cottontail rabbits (Sylvilagus floridanus alacer Bangs) received from southern Kansas, 11 have had spontaneously one or more of the papillomatous growths. These 11 cottontails were kept for observation and for a source of virus. With a single exception, our findings have agreed with those previously described., The history of the exceptional case follows: Cottontail rabbit S5-CR 363. Thin, young, adult male. Received March 30, 1935. On lower abdomen 4 pigmented warts were noted: A, 18×22×15 m. in height, B, C and D, 4-6 mm. in diameter x6-8 mm. in height. Rapid gain in weight. Papillomata appeared unchanged for 85 days, when lesion A showed superficial ulceration with thickening of the underlying tissues. Six days later the rabbit died from fracture of the lumbar spine sustained accidentally the previous day.