Rural hyper-endemic malaria in Tanganyika Territory

Abstract

1. 1. There is a real need for a detailed study of hyper-endemic malaria in African villages, in order to provide the necessary background to more summary observations in other parts. 2. 2. A survey of previous work shows that, while a few careful studies of this nature have been made in other parts of the world, Africa is not so fortunate. The previous observations recorded show that the findings in different countries cannot be fitted into a coherent whole. 3. 3. A description is given of the people studied, their diet, and their conditions of life, with some indication of the diseases to which they are subject and of the birth and death rates. 4. 4. There is a high prevalence of A. gambiae in. houses, and a mean sporozoite infectivity of 12-2 per cent. The infectivity has a seasonal rise to 24 per cent., at a time when there is an average of nearly 15 female anopheles to a house. 5. 5. In a detailed clinical description of the course of malarial infection in this untreated population, it is shown that all babies are infected within 5 months of birth, and that all have severe infections. 6. 6. This stage of acute infestation has passed its zenith after 18 months, and is succeeded by a period of malarial instability, during which the parasite count rises and falls irregularly. But symptoms are absent. 7. 7. After puberty symptoms are completely absent, and the general parasite level is a fiftieth or less of that which is present during infancy. 8. 8. The spleen rate is high, being 85 per cent., but it decreases with the parasite rate, as immunity is acquired. The largest spleens are found in babies soon after their first infection. 9. 9. There is a seasonal rise in the parasite infestation of man, which is chiefly confined to the non-immune and partially immune children. 10. 10. Gametocytes are found predominantly in children, at the time when immunity is just beginning to be established. Even if they are present in adults, they occur in very small numbers only. There is a great seasonal rise in the frequency and number of gametocytes in children under 5 years of age. 11. 11. P. falciparum is the dominant infection at all ages, but the other species (including P. ovale ) are also present during the first few years of life, and more rarely later. The immunity acquired to P. falciparum is less complete than that acquired to the other species. 12. 12. While children suffer from malaria during the first 2 years of life, and a few die during the first few months, older children cannot be said so to suffer, and no evidence was obtained of any harmful effects from malaria during adult life.