Spontaneous renal adenocarcinomas in the frog are presumed to be caused by a virus but not naturally transmitted between adult frogs. However, we have observed a high incidence of renal tumors in frogs maintained in the laboratory under crowded conditions in contrast to frogs housed under relatively uncrowded conditions. These results suggest that under laboratory conditions natural transmission or an unknown environmental factor(s) is important in the epidemiology of the frog renal adenocarcinoma.

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This investigation was supported by USPHS Research Grants No. CA-05755 and No. CA-06927 from the National Cancer Institute.

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