[House effect and family contamination in sleeping sickness: interpretative trial of the phenomenon. Study of 3 Congolese foci].

A review is given of the different hypotheses concerning the concentration of trypanosomiasis cases at the house or family level: 1. Mechanical transmission by haematophagous insects. 2. Interrupted feeding of a tsetse fly with cyclic infection on different people. 3. Family biological factor. These hypotheses are used as a introduction to an epidemiological field study in three congolese foci. Whereas their distribution among village districts is random, patients are significantly aggregated at the house and/or family level. This distribution may be partly explained by the behaviour of members of the family and community cells, associated with amplifying factors, the most probable being interrupted feeding of a tsetse fly with cyclic infection. In some foci other possibilities can be considered, such as mechanical transmission by Aedes or hereditary population factors. This spatial and/or familial concentration of cases is an important epidemiological property of sleeping sickness, the practical implication of which is the exhaustive survey of the human environment of cases.