[Use of molecular biology in the diagnosis of human African trypanosomiasis].

Human African trypanosomiasis (HAT), a.k.a. sleeping sickness, is still a major public health problem in sub-Saharan Africa. In West and Central Africa, this vector-borne parasitic disease in caused by Trypanosoma brucei gambiense transmitted by glossidinae. According to the classic model, HAT is characterized by two phases, i.e. the early circulating phase and the later neurological phase. Diagnosis from blood samples in the field and staging from cerebrospinal fluid samples in the laboratory are difficult due to the absence of specific clinical symptoms and fluctuating parasitemia levels. Several recent studies have described the use of the polymerase chain reaction (PCR) technique with primers specific for Trypanosoma brucei s.1 to improve the sensitivity and specificity of conventional test methods. Within the framework of active screening, PCR carried out on blood samples prior to serological tests could be helpful in identifying suspected infection. Although the one-time initial investment is high, expenditures on expendables is lower for PCR than conventional techniques (mAECt: miniature anion exchange column test) while achieving higher sensitivity. For application on cerebrospinal fluid samples, PCR also achieves better sensitivity than conventional techniques and thus can contribute to staging of the disease. Identification of the early or late phase is important for documenting successful therapy and early diagnosis of relapse. Further research will be needed before actual implementation. This is notably the case with regard to specificity since it is still not possible to assert that positive PCR is a sign of active infection by a pathogenic trypanosome in man.