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.Immunological approaches do, however, show some promise in this respect in that it is possible to relate the antigenic type to particular virulence characteristics, at least in mice. Nomenclature of trypanosome antigenic types requires to be improved and agreed so as to facilitate the integration of the work of different laboratories. Immunological methods have also improved disease survey, and tests such as immunofluorescence, and serum and cerebrospinal fluid IgM estimation, are now available. These tests may be applied conveniently on a large scale and to primitive populations. They powerfully complement the classical parasitological survey methods. Studies on the immunization of animals against trypanosomiasis have not yet yielded any method of practical application but are useful contributions to basic knowledge and have indicated areas in need of special investigation-such as the variety of antigenic types of the main pathogenic trypanosome species circulating in given areas of Africa, the stability of this "spectrum" of antigenic types in time, and the range of distribution in Africa of particular antigenic types.