Evaluation of Indirect Enzyme-Linked Immunosorbent Assay (ELISA) Systems for the Serodiagnosis of Bovine Trypanosomosis in Disease Endemic Areas of Kenya

Abstract

The present study was aimed at validating the performance of four indirect ELISA systems developed for the detection of anti-trypanosomal antibodies in bovine serum. The assay systems employed either native or denatured crude lysate antigens prepared from Trypanosoma congolense (Tc) Broaden 1904 and T. vivax (Tv) Ziemann 1905. Assay systems were designated as TcAGd, TcAGn, TvAGd or TvAGn, depending on the trypanosome species from which the antigen was prepared (Tc or Tv), and whether the antigen was denatured (AGd) or native (AGn). The microtitre plates used were precoated with these antigen preparations at the International Atomic Energy Agency (IAEA) laboratories in Vienna, Austria and shipped to Kenya. Diagnostic sensitivities and specificities were assessed using both known infected and uninfected bovine sera, respectively. All the positive samples were collected from cattle kept in trypanosomosis endemic areas of Galana and Ukunda in Coast province and Mfangano Island in Nyanza province of Kenya. Known negative sera were obtained from the KARI-TRC dairy farm. These animals are kept in a non-trypanosomosis endemic area in Muguga, near Nairobi, Kenya. Assay sensitivity ranged from 86% to 97% while specificity was between 82% and 100% depending on the assay system used. Systems employing denatured antigens had slightly higher, diagnostic sensitivity and specificity. The study has demonstrated that antigen pre-coated plates are useful in circumventing the problem of antigen instability. However, further studies need to be undertaken using larger sample sizes to determine if there are any significant differences between plates pre-coated with native and denatured antigens. The present version of indirect ELISA is a useful epidemiological tool that can be used in establishing the presence and extent of the disease.