Ricinus communis as a Source of a Potential Selective Rodenticide

In this country vole extermination represents a serious ecological problem. Birds of prey such as barn owls and buzzards fed on voles poisoned by azodrin may die as a result of secondary poisoning. The possibility of using ricin as vole-poison has been explored. Ricin (M.W. 65,000) was extracted and purified from Ricinus communis seeds. The LD50 (oral route) was 10 mg/kg for mice and voles whereas 1 mg/kg was lethal for all barn owls and buzzards to which it was administered. In these species 24 h after administration full toxic symptoms developed but they were delayed up to 3 days in voles. In these latter animals changes in levels of SGOT, SGPT, LDH, CPK, and cytochrome P-450 occurred after gavage of ricin and myocardial infarct necrosis was a salient histopathological finding. Discrete injection of ricin into vole intestinal tract showed that the duodenum was the major absorptive segment. Feeding barn owls and buzzards with voles previously poisoned with ricin did not affect the birds of prey, thus indicating that no secondary poisoning occurred.