Esophageal Tumors in Sheep: Some Ecological Observations

Summary

The occurrence of esophageal tumors in sheep on a large farm near Cradock, Cape Province, South Africa, is recorded. The tumors were found only during a 10-year period in which lambs were drenched with a mixture of nicotine sulfate and copper sulfate to combat internal parasites. During this time the sheep on a plateau grassland showed an incidence of over 8% of gullet tumor, while those grazing in scrub-covered valley bottoms and on hills did not show this condition. When the drench was changed, there was no further gullet tumor in the flocks. The tumors appear to be environmentally linked in some way. Their exact nature was not determined. Some tentative conclusions regarding the etiology of the tumors are proposed.