The present invention is directed to a filamentous bacteriophage for use in treating a neurodegenerative tauopathy or susceptibility to a neurodegenerative tauopathy and a method of using the bacteriophage for reducing the formation of fibrils of tau protein or for disaggregating pre-formed fibrils of tau protein, such as in a patient suffering from neurodegenerative tauopathy. The filamentous bacteriophage used in the present invention does not display (i) a mammalian cell internalization signal (ii) a &bgr；-amyloid antigen or an antibody to &bgr；-amyloid, or (iii) a tau protein antigen or an antibody to tau protein.
