Abstract
A new species of coccidium E. duodenalis sp.nov., has been described, from the pheasant. It is characterized by the subspherical shape of the oocyst, the lack of polar granules and the presence of large sporocystic residual bodies. Endogenous stages are found in the epithelial cells lining the villi, and occur chiefly in the duodenum and upper intestine. Second-generation merozoites form gametocytes and/or third-generation schizonts. The prepatent period is 5 days.E. duodenalis is moderately pathogenic, doses of 50 000 oocysts causing a 30% mortality and a significant weight loss in the survivors. Treatment with a range of sulphonamides in the drinking water was successful as was preventive treatment with Sulphaquinoxaline mixed with the food.Acknowledgements are due to Mr S. F. M. Davies for initiating this programme and carrying out a number of the animal inoculations, to Dr Helen Hein for help and advice in the design of the experiments and to Dr L. P. Joyner for advice in the preparation of the manuscript. The author also wishes to thank Miss C. N. Hebert for the statistical analysis of weight gains and Mr M. A. Peirce, Mr G. L. Choon, Miss J. Saddington and Miss M. Blore for technical assistance.

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