CARCINOMA IN THE LEOPARD FROG: ITS PROBABLE CAUSATION BY A VIRUS

Area of Science:

• Oncology
• Virology
• Amphibian Pathology

Background:

• Epithelial tumors with intranuclear inclusions are common in leopard frog kidneys.
• These tumors can be invasive adenocarcinomas that metastasize or more organized adenomas.

Purpose of the Study:

• To investigate the causative agent of kidney tumors in leopard frogs.
• To determine if the tumor is transmissible and if it is organ-specific.

Main Methods:

• Inoculation of leopard frogs with living tumor fragments or cell suspensions into various body cavities.
• Administration of desiccated and glycerinated tumor material.
• Observation of tumor development in inoculated frogs and control groups.
• Inoculation of alien frog species to test for organ specificity.

Main Results:

• Inoculation with living or treated tumor material did not result in significant local growth but led to kidney tumor development in approximately 20% of surviving leopard frogs.
• The incidence of kidney tumors in inoculated frogs significantly exceeded that in control groups.
• No tumors developed in alien frog species inoculated with the tumor material, indicating organ specificity.

Conclusions:

• The results strongly suggest an inclusion-forming, organ-specific virus as the cause of leopard frog kidney tumors.
• The findings support the viral etiology of these amphibian neoplasms.