Fluorescent Antibody Test for the Serodiagnosis of African and American Trypanosomiasis in Man

Abstract

A fluorescent antibody technique for the serodiagnosis of African and American trypanosomiasis in man is described. The test can be performed simply and rapidly through the use of trypanosomes in blood smears as antigen. There were extensive cross-reactions with sera from patients with other species of trypanosomes. Tests of sera from healthy controls and from patients with nontrypanosomal diseases and disorders revealed relatively few cross-reactions, indicating a high degree of specificity. The finding that dried blood on absorbent paper could be tested successfully with the FA technique may indicate its usefulness for studies in endemic areas. Human infections with African and American trypanosomiasis constitute important clinical and public health problems in large regions of the world. An unequivocal diagnosis of trypanosomiasis is often difficult to obtain since the clinical picture is not always well defined and the organisms frequently cannot be recovered by blood examinations. Consequently, there is a need for reliable, rapid, and inexpensive procedures which could provide the basis for an adequate diagnosis of these infections, especially during the latent and chronic phases of the disease. The fluorescent antibody technique (Coons et al., 1941) is rapidly developing into a practical, sensitive, and specific diagnostic method for several parasitic infections. Fife and Muschel (1959) described a fluorescent antibody technique (FA) for the serodiagnosis of Trypanosoma cruzi infections. T. cruzi cultured on a diphasic blood agar medium was utilized as a source of antigen. This technique, which required all the reactions to be carried out in test tubes to prevent drying of organisms, appeared to be less specific than the complementfixation test using purified T. cruzi antigen. Studies with T. rhodesiense and T. gambiense in experimental animals (Williams et al., 1963) have resulted in a rapid and practical FA technique which can be run on slides using as Received for publication 21 December 1962. antigen thin blood smears from infected rats. A technique for the use of minute amounts of dried blood in the fluorescent antibody test was developed recently (Anderson et al., 1961). This technique, which permitted mailing of specimens under adverse conditions, was found to be particularly useful in epidemiological surveys of schistosomiasis and trichinosis (Sadun et al., 1961, 1962). The current report summarizes results of studies in which the FA technique was used to stain fixed blood forms of T. rhodesiense, T. gambiense, and T. cruzi toward the development of a reliable and practical test for the laboratory diagnosis of African and American trypanosomiasis. The procedures were evaluated with sera obtained from humans in endemic areas. Furthermore, in the present work attempts were made to determine the degree of cross-reactivity of different trypanosome species and to determine whether blood smears dried on absorbent paper could be used in the serological diagnosis of trypanosomiasis. MATERIALS AND METHODS Sera: Human sera were obtained from individuals with well-documented trypanosomiasis infections. The diagnosis of trypanosomiasis in the patients was established by the recovery and identification of organisms from the blood or spinal fluid. To determine the specificity of the FA test, control sera from individuals with viral, bacterial, and parasitic infections other than trypanosomiasis were used. To test whether the presence of auto-