Publisher Summary The subgenus Trypanozoon contains several kinds of trypanosome, which are morphologically indistinguishable but differ in their behavior. At various times specific or subspecific status has been accorded to each kind, but, in recent years, those cyclically transmitted by tsetse in Africa have been separated into subspecies of Trypanosoma brucei , while the others, transmitted non-cyclically outside the African tsetse belts, have retained separate species status. However, although such new terminology may be more correct taxonomically, the practical problems of distinguishing the trypanosomes remain. Enzyme electrophoresis is being used on an increasingly wide scale for the intrinsic characterization. However, as the number of enzyme systems being used for identification grows, comparison of stocks becomes increasingly difficult and intricate, particularly when an enzyme occurs in a multibanded form after electrophoresis. After using 12 enzyme systems to characterize 160 Trypanozoon stocks, the results have been analyzed to establish the degree of relatedness of each of the 59 zymodemest encountered. The detailed analysis is presented in this chapter.

Numerical analysis of enzyme polymorphism: a new approach to the epidemiology and taxonomy of trypanosomes of the subgenus Trypanozoon.

There is a dramatic resurgence of human African trypanosomiasis (HAT) in sub-Saharan Africa. T.b. gambiense is spreading epidemically in large areas of Central Africa, especially the Southern Sudan, Congo-Zaire, Angola, Uganda and the Central African Republic. Devastating epidemics of T.b. rhodesiense have occurred in south-eastern Uganda. The causes of the re-emergence of sleeping sickness as a public health problem include widespread civil disturbance and war, declining economies, reduced health financing and the dismantling of disease control programmes. Despite the inevitably fatal outcome without treatment, HAT is often given low priority by donors and national governments. The advances made in diagnosis, treatment and vector control have not been sufficiently implemented. To limit the human impact in some of the poorest communities in Africa, endemic countries will require external support to implement strategies for disease control. Donor agencies, NGOs and mission organisations could play an important role in supporting control efforts. National authorities will need to control and co-ordinate these efforts with assistance from WHO and the international community.

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Human African trypanosomiasis: an emerging public health crisis

The history of human sleeping sickness in East Africa is characterized by the appearance of disease epidemics interspersed by long periods of endemicity. Despite the presence of the tsetse fly in large areas of East Africa, these epidemics tend to occur multiply in specific regions or foci rather than spreading over vast areas. Many theories have been proposed to explain this phenomenon, but recent molecular approaches and detailed analyses of epidemics have highlighted the stability of human-infective trypanosome strains within these foci. The new molecular data, taken alongside the history and biology of human sleeping sickness, are beginning to highlight the important factors involved in the generation of epidemics. Specific, human-infective trypanosome strains may be associated with each focus, which, in the presence of the right conditions, can be responsible for the generation of an epidemic. Changes in agricultural practice, favoring the presence of tsetse flies, and the important contribution of domestic animals as a reservoir for the parasite are key factors in the maintenance of such epidemics. This review examines the contribution of molecular and genetic data to our understanding of the epidemiology and history of human sleeping sickness in East Africa.

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History of Sleeping Sickness in East Africa

Will the real Trypanosoma b. gambiense please stand up.

Publisher Summary This chapter focuses on the factors affecting immunity in both nonpregnant and pregnant women and on the chronicity of several infections that are carried through successive pregnancies with adverse consequences for mother and child. It considers risks to women of reproductive age to differ from men of equivalent years. Ensuring a reduction in the parasitic burden of women of reproductive age is the first step in reducing fetal infection and sensitization and in influencing the pathological pattern of parasitic disease in communities living in endemic areas. The practical and research implications of considering women as a special risk group for complications of parasitic infection are considerable and should lead to the development and implementation of improved control strategies. Health planners need to recognize that parasitic infection has serious consequences in pregnant women and primary health care services must be better equipped to detect and manage infections during pregnancy and between pregnancies. This chapter reviews those infections that are primarily identified by the Special Program for Research and Training in Tropical Diseases (World Health Organization) as being of particular public health concern (onchocerciasis, filariasis, schistosomiasis, malaria, African trypanosomiasis, and leishmaniases), although reference to other infections is made where relevant.

Parasitic infections in women and their consequences.

The history is given of sleeping sickness, of both the Gambian and Rhodesian types, in Nyanza Region, Kenya, leading up to the explosive outbreak, in Alego and the surrounding locations in 1964, of T. rhodesiense infections transmitted by G. fuscipes ( G. palpalis fuscipes ). Some account is given of the characteristics of this epidemic, of the conditions that may have contributed to it and of the danger of spread to other parts of Kenya. Since this epidemic is in marked contrast to the normal association of T. gambiense with tsetse of the G. palpalis group, and of T. rhodesiense with the G. morsitans group, the reasons for these associations are considered and it is concluded that the usual combinations are the result of selective factors operating in the different conditions in which the trypanosome strains are transmitted. Laboratory and field evidence is quoted to show that there is no reason why, given suitable conditions, either type of trypanosome should not be transmitted by tsetse of either group. It is suggested that the recorded history of the movement of infected persons, the belief then current that G. morsitans did not transmit sleeping sickness, and the early incidence and localization of cases in Nyasaland and Northern Rhodesia, are consistent with the conclusion that, about 1908, a virulent strain, or strains, of Trypanosoma infective to human beings was imported from the epidemic areas of the Congo to parts of Nyasaland and Northern Rhodesia infested with tsetse of the G. morsitans group, and that this strain, or strains, capable of infecting game animals and being re-transmitted from them, gave rise to what is now known as T. rhodesiense .

Some observations on the recent epidemiology of sleeping sickness in Nyanza Region, Kenya, and its relation to the general epidemiology of Gambian and Rhodesian sleeping sickness in Africa.

K. C. Willett

Papers

Some observations on the recent epidemiology of sleeping sickness in Nyanza Region, Kenya, and its relation to the general epidemiology of Gambian and Rhodesian sleeping sickness in Africa.