Some principles of the epidemiology of human trypanosomiasis in Africa

Human trypanosomiasis in Africa is treated as a disease complex in which three main elements are involved, the vertebrate host, the parasite and the insect vector, and the epidemiology is discussed in terms of the three pairs of relationships between these elements.Under host-vector relationships the significance of the type of man-fly contact is pointed out and an outline given of how it may be determined, and transmission of the disease influenced, by human activities, climatic factors and other conditions, in both Trypanosoma gambiense and T. rhodesiense sleeping-sickness.Under host-parasite relations consideration is given to the question of reservoir hosts, variations between human-infective strains in virulence, infectivity to animals and response to chemotherapy, and the relationships of these factors to one another and to the epidemiology of the disease.The complexity of factors involved in vector-parasite relations is discussed and the need for fuller information on the relative importance of these factors is stressed.     

Trends in research on the immunology of trypanosomiasis

It was thought timely, in view of the increasingly close association between immunology and parasitology, to attempt a synthesis of research on trypanosomiasis immunology—research which may be expected both to lead to the solution of practical problems in this disease and to provide models for the study of basic immunological problems.     

Some principles of epidemiologic studies.

The use of epidemiological evidence is frequently involved in clinical decision making. Usually epidemiological investigation seeks to determine the extent of the association between a suspected factor and the occurrence of a disease. When the data are collected retrospectively then rates of exposure to the factor are compared for a group of cases of the disease and a group of controls. If the study is prospective then incidence rates of the disease are compared for a group exposed to the factor and an unexposed group. Although the retrospective approach is often more feasible it is also more vulnerable to bias. The possible influence of bias and chance must be taken into consideration when interpreting the results of any study. Relative risk serves as a useful index for expressing the strength of the association between the factor and the disease.     

Some current problems in the sero-immunology of trypanosomiasis in relation to the epidemiology and control of the disease

The author draws attention to the need for accurate epidemiological information so that control programmes may be properly orientated and he emphasizes that we are still at a loss in this respect in the case of trypanosomiasis, as we still lack methods to recognize, among the assemblage of natural trypanosome populations with identical morphology, those populations that have the biological capabilities to produce disease in man and his domestic stock.     

Future prospects for the chemotherapy of human trypanosomiasis. 1. Novel approaches to the chemotherapy of trypanosomiasis

Chemotherapy of trypanosomiasis and leishmaniasis is far from satisfactory and the discovery of new drugs has been slow. Emphasis on the empirical approach to drug development is now shifting towards a more rational, directed approach, which employs the modern tools of science. This is illustrated with respect to the newly discovered drug target, trypanothione, a unique metabolite which is critical for survival of Trypanosoma and Leishmania and absent from the host.     

Towards the Atlas of human African trypanosomiasis

Background  

Updated, accurate and comprehensive information on the distribution of human African trypanosomiasis (HAT), also known as sleeping sickness, is critically important to plan and monitor control activities. We describe input data, methodology, preliminary results and future prospects of the HAT Atlas initiative, which will allow major improvements in the understanding of the spatial distribution of the disease.     

Future prospects for the chemotherapy of human trypanosomiasis. 2. Combination chemotherapy and African trypanosomiasis

This paper reviews the progress which has been achieved with combination chemotherapy of experimental murine central nervous system trypanosomiasis. Successful treatments have been achieved with suramin followed by 5-nitroimidazoles; difluoromethylornithine in combination with bleomycin, 9-deazainosine, suramin, arsenicals, antimonials and diamidines; and also the arsenicals in combination with the 5-nitroimidazoles or nifurtimox. Pretreatment with prednisolone and azathioprine, to minimize reactive encephalopathies, and supportive treatment with oxygen are both indicated.