This study of the anemia produced by P. lophurae in ducks emphasizes the significance of a decrease in the number of red cells in this disease, and furthermore, it suggests that the rapid diminution in the number of parasites following the peak of the parasitemia may be directly related to the character of this anemia since these parasites apparently do not prefer young erythroblasts to mature erythrocytes.
The observations made in this study show that erythrocytes in the ducks first appear as spherical bodies in stained smears and when mature they are elliptical in shape. Under abnormal conditions such as may occur with a severe parasitemia, erythroblasts appear in the peripheral blood in large numbers, sometimes almost completely replacing the adult type of red cell. Both microcytes and macrocytes appear in the blood stream. The amount of hemoglobin within some of these young erythrocytes is small as indicated by the hemoglobin determinations and the staining reaction. Small young erythroblasts with little hemoglobin appear in the peripheral blood when the maximum load is placed upon the hematopoietic tissues.