Evaluation of ELISA using crude Trypanosoma brucei brucei antigen and CATT in the detection of human African trypanosomiasis

Abstract

An antibody Enzyme Linked Immunosorbent Assay (ELISA) for the detection of parasite induced IgG
and IgM using excretory-secretory products of Trypanosoma brucei brucei (T. b. brucei) as antigen was carried out on
human sera and cerebrospinal fluid samples collected from a field survey. Card Agglutination Technique for
Trypanosomiasis (CATT) was also performed on dried blood samples from the same subjects. Anti-trypanosome
antibody was detected in 85.7% and 74.5% of the 98 samples using ELISA and CATT respectively, 36 of these
subjects were confirmed parasite positive, 57 were negative and 5 were non-endemic controls. The sensitivity of the
assays using sera from parasite-positive cases for the detection of antibodies by ELISA (IgG + IgM) was 100% and
94.4% for CATT. The sensitivity of the antibody detection assay was 77.8% for IgG and 88.9% for IgM respectively
and the specificity was 60% for CATT, 40% IgG and 100% IgM. A statistically significant relationship between IgM
titres and parasite presence in subjects (P < 0.05) was observed. Thirteen CSF samples from 6 parasite positive and 7
aparasitaemic subjects were analyzed. IgG antibodies were detected in 7 (53.8%) and IgM in 6 (42.2%) of these. The
specificity of the ELISA assays was 46.2% (IgG), 53.8% (IgM) and sensitivity was 66.7%. The findings of this study
showed that the crude extract of T. b. brucei was highly immunogenic and the antibody ELISA using this antigen was
more specific than CATT in the diagnosis of human trypanosomiasis. The field sensitivity and application of CATT in
field survey was also highlighted.
Key Words: African Trypanosomiasis; Trypanosoma brucei brucei; ELISA; CATT; Detection of trypanosomes.