1. 1. The results of various studies by other workers on the spleen and parasite rates in Indians, Malays and Bantu are summarized. 2. 2. The results of our own observations on Khonds in India, and on Masai and Bantu in East Africa are also summarized and compared with the foregoing and with one another. 3. 3. It is pointed out that wide differences may be found in the malarial status of communities in the same country and, in the case of the Bantu, of the same race; while close similarities occur in different countries. 4. 4. The results of experimental infections in birds and monkeys are cited and interpreted in terms of the two states of allergy and immunity. The probable significance of these is illustrated by reference to the role of the two states in tuberculosis. 5. 5. It is suggested that the observed contrasts in the spleen and parasite rates in diverse communities may also be explained in terms of immunity and hypersensitivity. 6. 6. It is concluded that the immune status is dependent not on race but on the frequency of infection; and that the most accurate index of endemicity is the frequency of infections in the non-immune, that is the rate in early infancy. 7. 7. While a consideration of the Spleen Rate and Endemic Index may be of value in forming an estimate of endemicity and immunity when similar communities are being compared, these indices may be misleading when the epidemiological surroundings are dissimilar. 8. 8. A consideration of the variation with age in the spleen and parasite rates throws more light on endemicity and immunity and on such variation a rough classification may be made into immune and sub-immune communities. 9. 9. But it is suggested that by far the most sensitive index at present available for field studies is the average parasite count, and its variation with age. c 1937.
There has been little change since 1955 in the laboratory techniques for seeking new antifilarial compounds, although one valuable addition to laboratory study has been the experimental infection of cats with Brugia malayi.The chief drug for the treatment and control of filariasis-whether caused by Wuchereria bancrofti or by B. malayi-continues to be diethylcarbamazine, and the author reviews the reports recently published on its use. In India and China large-scale campaigns involving the use of this drug have been undertaken; and in Tahiti filariasis has been suppressed and almost eliminated. Campaigns on a smaller scale and pilot projects considered in this survey include those conducted in Pacific islands, Malaya, Ceylon, Brazil, Surinam and East and West Africa.It is generally agreed that the administration of diethylcarbamazine produces a great diminution in the microfilarial counts of those taking it, and in many persons both microfilariae and adult worms are eradicated. The difficulties which arise are due to toxic effects which occur in some recipients and which may adversely affect the acceptability of treatment.
The particular agricultural adaptation we have been considering is the ultimate determinant of the presence of malaria parasites in the intracellular environment of the human red blood cell. This change in the cellular environment is deleterious for normal individuals, but individuals with the sickle-cell gene are capable of changing their red-cell environment so that intense parasitism never develops. Normal individuals suffer higher mortality rates and lower fertility rates in a malarious environment than individuals with the sickle-cell trait do, so the latter contribute proportionately more people to succeeding generations.
Matched MeSH terms: Africa, Eastern; Africa, Western