1. A certain percentage of South African sheep kept locally become “carriers” of anaplasma. The course of the disease is evidently of such a mild nature that it has never been identified naturally.
2. When sheep introduced from some other centres in Union are injected with the blood of such carriers, reactions of anaplasmosis are set up. Such a disease, as regards its course, symptoms, and the nature of anaplasma, resembles a mild form of bovine anaplasmosis described by Theiler. The disease was propagated in sheep for eleven generations by means of blood-inoculations.
3. When carriers of ovine anaplasma are splenectomized, grave symptoms of anaplasmosis are set, which in some instances prove fatal.
4. In the same way splenectomy of equines, carriers of nuttallia, was followed by a relapse of nuttalliosis with fatal results. In case of bovines, relapses of anaplasmosis alone, or combined with piroplasmosis and gonderiosis, followed. In the latter instance it was shown that bovines reared locally were not necessarily carriers of anaplasma and piroplasma simultaneously.
5. The reactions of anaplasmosis in splenectomized sheep were protracted over long periods, with remissions from time to time.
6. The blood-changes in the splenectomized infected sheep were associated with a marked oligocythaemia, the appearance of erythroblasts, normoblasts, and jolly-bodies. With reference to the leucocytes, first a neutrophilia was noted, then a monocytosis with erythrophagocytosis and a lymphocytosis developed, and in some instances an eosinophilia.
7. It would appear that the neutrophilia is associated with the operation of splenectomy, the monocytosis with the removal of “degenerated” and “damaged” erythrocytes, the lymphocytes seem to have some association with the return to normal of the erythrocytes, and the eosinophilia seem to stand in some relation to the removal of the spleen.
8. The operation of splenectomy in susceptible equines, bovines, goats, and ovines was carried out with practically no impairment. A transitory polyglobuly and neutrophilia were seen in some of the cases.
9. Susceptible and splenectomized susceptible bovines failed to react to “ovine” anaplasma, nor did such “bovines” become carriers of “ovine” anaplasma.
10. Non-splenectomized local goats could not be infected with “ovine” anaplasma, whereas splenectomized local goats only showed the presence of parasites in the blood after a prolonged incubation period.
11. Susceptible and splenectomized ovines could not become infected with “bovine” anaplasma, nor did such ovines become carriers of “bovine” anaplasma.
12. Anaplasmosis in sheep, except for a few instances where Gonderia ovis was seen, could in no way be connected with a stage in the life-cycle of a piroplasmosis.
13. All attempts made to show that anaplasmosis of sheep was associated with a filterable virus failed.
14. It was shown that anaplasma retained its vitality to infect. susceptible sheep when stored in citrate for one week, three weeks, five weeks, and in one case for nine weeks.
15. No difficulty was experienced in differentiating between “anaplasma” and “jolly-bodies.”
16. The “chromatin-bodies” produced by drugs, like pyrogallic acid, were “jolly-bodies” and associated with an oligocythaemia and had nothing whatsoever to do with “anaplasma.”
17. In view of the results arrived at in this paper, and on account of fatal “relapses of malaria” reported to have occurred in human beings after the removal of the spleen, splenectomy in man ought to be carefully considered when undertaken in malarial regions.