Adaptation and validation of antibody-ELISA using dried blood spots on filter paper for epidemiological surveys of tsetse-transmitted trypanosomosis in cattle

The indirect enzyme-linked immunosorbent assay (ELISA) for the detection of anti trypanosomal antibodies in bovine serum was adapted for use with drie d blood spots on filter paper. Absorbance (450 nm) results for samples were expressed as percent positivit y, i.e. percentage of the median absorbance result of four replicates of th e strong positive control serum. The antibody-ELISA was evaluated in Zambia for use in epidemiological surve ys of the prevalence of tsetse-transmitted bovine trypanosomosis. Known neg ative samples (sera, n=209; blood spots, n=466) were obtained from cattle f rom closed herds in tsetse-free areas close to Lusaka. Known positive sampl es (sera, n=367; blood spots, n=278) were obtained from cattle in Zambia's Central, Lusaka and Eastern Provinces, diagnosed as being infected with Try panosoma brucei, ir: congolense, or T. vivax using the phase-contrast buffy -coat technique or Giemsa-stained thick and thin blood smears. For sera (at a cut-off value of 23.0% positivity) sensitivity and specificity were 86.1 and 95.2%, respectively. For bloodspots (at a cut-off value of 18.8% posit ivity) sensitivity and specificity were 96.8 and 95.7%, respectively. The i mplications of persistence of antibodies following treatment or self-cure a re discussed. (C) 1998 Published by Elsevier Science B.V. All rights reserv ed.