Field diagnosis of sleeping sickness in the Ivory Coast. I. Comparison of the miniature anion-exchange/centrifugation technique with other protozoological methods

The miniature anion-exchange/centrifugation (m-AEC) technique for the detection of trypanosomes in blood was tried out as a field diagnostic method for African sleeping sickness among populations exposed to natural infection in the vicinity of Daloa, République de la Côte d'Ivoire. It was compared with the two other protozoological techniques in common use in Africa, namely, the microhaematocrit buffy-coat microscopy (MBCM) method and the thick blood film (TBF). A laboratory study on a small number of known infected subjects and two field-survey studies, all showed the m-AEC method to be more sensitive than the MBCM and very much more sensitive than the TBF. The m-AEC method detected many cases that were missed by one or other, or both, of the other tests. The m-AEC method has, also, other advantages. The duration of critical microscopy required is limited. It is faster in operation when large numbers of subjects are concerned than is the MBCM. It offers, with no additional operation beyond filling the eluates into suitable tubes, samples of diluted plasma which may be used for serology. Thus a very efficient survey procedure can be envisaged: first the m-AEC test, selecting infected subjects for immediate treatment; second, re-examining, by the m-AEC method, on a subsequent visit, those other subjects suspect on the basis of the serological examination of the eluates. The complexities of the preparation of materials and procedures, which hitherto have inhibited general application in the field of techniques involving anion-exchange, have been avoided by miniaturization and by the pre-preparation of apparatus and materials at a base laboratory.