Bovine spongiform encephalopathy (BSE) is a neurological disease of cattle. Antibody responses to Acinetobacter radioresistens and six other bacteria, as well as to bovine myelin basic protein and bovine neurofilaments were measured in 128 BSE positive animals, 63 BSE negative animals and 64 healthy control animals. Animals positive for BSE had the highest levels of antibodies to Acinetobacter radioresistens (p < 0.0001) and also autoantibodies to bovine myelin basic protein (p < 0.0001) and bovine neurofilaments (p < 0.0001). In an endeavour to develop an antemortem test for BSE, 12 different strains of Acinetobacter were further tested in a MAN (myelin-Acinetobacter-neurofilament) assay involving 28 BSE positive and 18 BSE negative animals and defined bovine brain peptides. Five out of the 12 Acinetobacter bacteria tested [Acinetobacter (sp3), A. haemolyticus (sp4), A. johnsonii (sp7), A. lwoffii (sp8) and Acinetobacter (sp9)] gave 100% sensitivity and 100% specificity for detecting BSE. The highest anti-bacterial antibody level compared to controls was obtained with A. johnsonii. Further field studies are required to determine the validity of the MAN assay in detecting animals affected with BSE.